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784 terms

Bio 1 Lec, Spring 08

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cell
organism's basic units of structure and function
cell theory
fundamental unit; all calls come from preexisting cells; contain hereditary information which is passed from cell to cell during cell division; All known living things are made up of cells
prokaryotic cells
lack membrane-bound organelles; lack a nucleus; contain DNA, butplasma membrane present not in a separate compartment); smaller than eukaryotic; almost always have tough external wall; single-celled organisms (Archaea and Bacteria);
eukaryotic cells
have membrane-bound organelles; have membrane-bound nucleus (with DNA inside); larger than prokaryotic; some have a tough outer wall (plants); single and multicellular (animals, plants, fungi, protists); plasma membrane present
taxonomic scheme
kingdom, phylum, class, order, family, genus, species
three domains
Bacteria (prokaryotic cells); Archaea (prokaryotic cells); Eukarya (eukaryotic cells)
bacteria
single-celled organisms; diverse and widespread; less extreme environments
archaea
single-celled organisms; extreme environments (salty lakes, hot springs)
eukarya
single- and multi-celled organisms
hierarchy of organization (micro)
(in order) atoms, complex biological molecules (macromolecules), subcellular organelles, cells, tissues, organs, organ systems, complex organism
hierarchy of organization (macro)
(in order) population, community, ecosystem, biome, biosphere
properties & processes associated with life
order, reproduction-biogenesis, energy utilization (processing), growth and development, response to environment, homeostasis, evolutionary adaptations
cells (history)
1665 Robert Hooke named them; 1600's Antonie van Leeuwenhok first saw a live cell; 1839 Matthias Schleiden & Theodor Schwann came up with the cell theory
cytoplasm
The entire contents of the cell, exclusive of the nucleus, and bounded by the plasma membrane.
nucleus
the chromosome-containing organelle of a eukaryotic cell
organelle
Structure inside eukaryotic cells that performs specialized functions.
eukaryotic kingdoms
plantae; animalia: fungi; protists
plante
part of (1 of 4) the eukaryotic kingdom, multicellular, phtosynthetic autotrophs
animalia
part of (2 of 4) the eukaryotic kingdom, multicellular, ingest other organisms
fungi
part of (3 of 4) the eukaryotic kingdom, decomposers, absorb nutrients after breaking them down
protists (multiple kingdoms)
unicellular and simple multicellular
what links all forms of life (similarities)?
universal genetic code, similarity in cell structure, glycolysis is a widespread metabolic pathway, regulatory mechanisms, evolution
glycolysis
The splitting of glucose into pyruvate. This is the one metabolic pathway that occurs in all living cells, serving as the starting point for fermentation or aerobic respiration.
homeostasis
the ability to maintain a relatively constant internal environment in the presence of a changing external environment (steady-state physiological condition of the body). uses negative and positive feedback
matter
anything that takes up space and has mass; organisms are composed of matter
atoms
the smallest component of an element that still has properties of the element, consisting of a positively charged nucleus surrounded by a charged cloud of electrons.
96% and 4% of living matter are made of these elements
C, O, H, N and P, S, Ca, K, Na, Cl, Mg
isotope
atoms with the same number of protons and electrons, but different numbers of neutrons
ion
atom or molecule that has a change due to gain or loss of an electron
element
matter composed of atoms that all have the same atomic number (protons)
compound
substance consisting of 2 or more elements in a fixed ratio (does not necessarily have the same traits as its elements)
valence
indicates how many electrons an atom is missing from its outermost shell (2 for first ring, 8 for all rings after that). Indicates the number of bonds an atom is likely to form
energy
capacity to cause change
potential energy
energy mater has because of its location or structure (electrons of an atom differ in their amounts of potential energy)
energy level (electron shell)
an electron's state of potential energy
What is the chemical behavior of an atom determined by?
the distribution of electrons in the levels/shells (by the valence) (elements with full outer shells are chemically inert)
what is the valence of oxygen (atomic #8)?
-2
what is the valence of carbon (atomic #6)?
-4
orbital
three-dimensional space where electrons are found 90% of the time (each electron shell (level) has a specific number of orbitals (2 and 8))
electronegativity
an atom's attraction for the electron in a bond; the more electronegative an atom, the more strongly it pulls shared electrons toward itself
covalent bonds
sharing of outermost electrons between atoms, very strong; nonpolar covalent bond and polar covalent bond
nonpolar covalent bond
electrons equally distributed between atoms of molecule; not water soluble (hydrophobic); most common in biological matter
polar covalent bond
electrons pulled toward more electronegative atom of molecule; water soluble (hydrophilic)
Ionic bonds
one atom strips electrons from bonding partner; compound held together by attraction between cation & anion; weaker than covalent bonds
cation
ion with a po, positively charged ion (lost electrons)
anion
negatively charged ion (gained electrons)
hydrogen bond
weak attraction between a slightly positive H and another slightly negative atom (usually O or N). results in many properties of water
hot spots
electrons distributed asymmetrically in molecules or atoms
van der Waals interactions
attractions as a result of hot spots between molecules that are close together
proton
particle in the nucleus with a positive charge of +1 and an atomic mass number of 1 Dalton.
neutron
a non-charged nuclear particle with the same mass as the proton
electron
negatively charged particle (-1) with a mass 1/1837 of that of a proton
list bond strength from highest to lowest
nonpolar covalent bonds; polar covalent bonds; ionic bond; hydrogen bond; van der Waals interactions
strongest bonds in organisms
covalent bonds, form cell's molecules
what do the weak chemical bonds do?
reinforce shapes of large molecules and help molecules adhere to each other
charged molecules, what kind of bonds?
ionic or polar covalent (water, salt)
uncharged molecules, what kind of bonds?
nonpolar covalent (oils)
molecular shape
biological molecules reconize and interet with each other based on molecular shape; similar shapes, similar functions; change the shape, change the function
reaction (rxn)
makinga nd breaking chemical bonds, leads to changes in composition of matter
chemical equilibrium
point at which there is no net change of concentrations of reactants and products
water facts
3/4 of planet; organisms are 70-95% water; could be prerec for life
water characteristics
cohesive behavior; ability to moderate temp; expansion upon freezing; versatile solvent
cohesion
clinging together of molecules of same substance
adhesion
clinging together of molecules of different substances
surface tension
measure of how difficult to stretch/break surface of liquid
kinetic energy
energy of motion
heat
measure of total amount of kinetic energy due to molecular motion
temperature
measures intensity of heat due to average kinetic energy of molecules
calorie (cal)
amount of heat required to raise temp of 1g of water by 1C
kcal
kilocalories (1,000cal); what you see on food packages
joule (J)
unit of energy where 1J = 0.239 cal; 1 cal = 4.184 J
specific heat
amount of heat that ust be absorbed or lost for 1g of substance to change temp by 1 degree C
water's specific heat
1 cal/g/degree C; (very high, water is resistant to temp change)
why is water's specific heat high?
breaking H bonds in water requires energy before you even get the actual molecules to move faster (to heat up)
implications of water's specific heat
moderates coastal temp; stabilizes earth temp; organisms can maintain stable temp
evaporative cooling
hottest molecule in liquid is most likely to leave, so temp decreases
properties of ice
floats in liquid water because H bonds in ice are more ordered; water reaches greatest density @4C
ice implications
if ice sank, no life in the oceans because lakes/ocean would not thaw out
solution
a solute dissolved in a solvent (ex: salt water = salt (solute) in water (solvent)
mole
Avogadro's number (6.023 * 10^23) of molecules
1 molar solution
1 mole of molecules dissolved in solvent to make 1L total solution
water's solvent properties
polar molecule; small; can deal with cations and anions; can also dissolve other polar molecules
hydration shell/sphere
when ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules
hyrophillic
water-loving (ionic, polar molecules)
hydrophobic
water-fearing (oily molecules)
acid
solution with H+ higher than water (ex: vinegar). release H+
base
solution with H+ lower than water (ex: bleach); soak-up H+
pH
=log 1/H+
key to an atom's chemical characteristics
electron configuration, which determines the kinds and number of bonds an atom will form
tetravalence
having 4 valence electrons
3D shape of carbon atom with 4 single covalent bonds
the bonds angle toward the corners of an imaginary tetrahedron (~109.5 degrees)
3D shape of molecule with two carbon atoms that are joined by a double bond
flat (all bonds are on the same plane)
carbon's most frequent partners
oxygen, hydrogen and nitrogen
four major atomic components of organic molecules
carbon, oxygen, hydrogen and nitrogen
hydrocarbons
organic molecules consisting of only carbon and hydrogen; hydrophobic; can undergo reactions that release a large amount of energy
adipose cells
fat cells: long hydrocarbon tails attached to a nonhydrocarbon component
isomers
compounds that have the same numbers of atoms of the same elements but different structures and hence different properties (three types: structural isomers, geometric isomers, enantiomers)
structural isomers
differ in the covalent arrangements of their atoms
geometric isomers
have the same covalent partnerships, but they differ in their spatial arrangements (cis isomer and trans isomer)
geometric isomers arise from what?
the inflexibility of double bonds
enantiomers
isomers that are mirror images of each other; biological enzymes act on only 1 enantiomer
asymmetric carbon
a carbon atom that is attached to four different atoms or groups of atoms
steroid
organic molecules with a common carbon skeleton in the form of 4 fused rings
functional groups
characteristic groups often attached to skeletons of organic molecules, determine chemical properties; most commonly involved in chemical rxns
The functional groups most important in the chemistry of life
hydroxyl; carbonyl; carboxyl; amino; sulfhydryl; phosphate; methyl (not as important)
hydroxyl group
structure = -OH; compound = alcohols; ex: ethanol; functional properties: polar, can form hydrogen bonds with water, helping dissolve organic compounds such as sugars
carbonyl group
structure: >CO; compound: ketones (within a carbon skeleton) and aldehydes (at the end of the carbon skeleton); ex: acetone (ketone) and propanal (aldehyde); a ketone and an aldehyde may be structural isomers with different properties, also found in sugars, giving rise o two major groups of sugars: aldoses and ketoses
carboxyl group
structure: -COOH; compound: carboxylic acids; ex: acetic acid; properties: acidic,found in cells in the ionized (-1) form
amino group
structure-NH2; name of compound: amines; ex: glycine; properties: basic, ionized (+1) under cellular conditions
sulfhydryl group
structure: -SH; compound: thiols; ex: cysteine; properties: two sulfhydryl groups can react, forming a covalent bond, which helps stabilize protein structure. cross=linking of cysteines in hair proteins maintains the curliness or straightness of hair
phosphate group
structure: -OPO3(-2); compound: organic phosphates; ex: glycerol phosphate; properties: contributes negative charge to the molecule of which it is a part, has the potential to react with water, releasing energy
methyl group
structure: CH3; compound: methylated compounds; ex: 5-methyl cytidine; properties: addition of a methyl group to DNA affects expression of genes, arrangement of methyl groups in male and femal sex hormones affects their shape and function
adenosine triphosphate (ATP)
one of the three phosphates may be split off as a result of a reaction in water, releasing energy
macromolecule
a giant molecule formed by the joining of smaller molecules, usually by a condensation reaction (a covalent connection)
polymer
long molecule consisting of many similar or identical building blocks linked by covalent bonds
monomers
repeating units that serve as the building blocks of a polymer
condensation synthesis
a reaction in which 2 monomers are combined covalently through the removal of a small molecule (when the small molecule is water, it is called dehydration reaction)
enzymes
specialized macromolecules that speed up chemical reactions in cells
hydrolysis
disassembles polymers into monomers, a reverse of the dehydration reaction
four main classes of large biological molecules? What are their monomer forms?
carbohydrates (sugar), lipids (fatty acids), proteins (amino acids), nucleic acids (nucleotides);
carbohydrate
general form = CH2O; names end in "ose"; water soluble, form rings in water; taste sweet; often pentoses or hexoses (5,6 carbons)
monosaccharides
the simplest carbohydrate. known as simple sugars, monosaccharides have molecular formulas that are generally some multiple of CH2O; classified by location of carbonyl group and # of carbons in carbon skeleton
disaccharide
2 monosaccharides strung together
monosaccharide examples
glucose; fructose; galactose
disaccharide examples
sucrose (glucose + fructose); lactose (glucose + galactose); maltose (glucose + glucose)
when do sugars often form into rings?
in aqueous solutions
polysaccharide
polymer of more than 2 monosaccharides; important in metabolism; sometimes used for cell I.D.; store energy; structure/function determined by monomers & locations of bonds between monomers
starch (amylose) & glycogen
polysaccharides of thousands of glucoses; store energy; allows organisms to store thousands of glucoses in 1 polysaccharide molecule. The glycogen breaks down glucose in the digestive tract, and is synthesized from glucose in the liver
what do plants use for energy storage?
starch
what do animals use for energy storage
glycogen
cellulose
a polymer of glucose; a major component of the tough wall of plant cells
∝ glucose
are helical; form starch
ß glucose
are straight; form cellulose; H atoms on one strand can bond with OH groups on other strands. parallel cellulose molecules held together this way are grouped into microfibrils, which form strong building materials for plants
why does cellulose in human food passes through the digestive tract as insoluble fiber?
enzymes that digest starch by hydrolyzing ∝ linkages can't hydrolyze ß linkages in cellulose
why can many herbivores, from cows to termites, digest cellulose (∝ glucose)?
have symbiotic relationships with microbes that use enzymes to digest cellulose
chitin (pronounced "kite-en")
a structural polysaccharide; found in the exoskeleton of arthropods; provides structural support for the cell walls of many fungi; used to make surgical thread; Like cellulose, but with nitrogen
lipids
only class of large biological molecules that do not form polymers; hydraphobic (consist mostly of hydrocarbons, which form nonpolar bonds); some are 'polymers' of fatty acid
important lipids
fats; phospholipids; steroids
triglycerides
composed of glycerol and fatty acids; OH from glycerol and H from fatty acid break off in a dehydration reaction
saturated fats
no C=C double bonds; have max # of hydrogen atoms; animal fats; solid at room temp
unsaturated fats
one or more C=C double bonds; vegetable fats; fish fats; liquid at room temp
fats related to diet
saturated fats contribute to cardiovascular disease through plaque deposits; trans fats (hydrogenated unsaturated fats) may be even more unheathly
hydrogenation
process of converting unsaturated fats to saturated fats by adding hydrogen
trans fats
partially hydrogenated oils (margarine, crisco); solid at room temp; found in almost all processed food (cis = H on same side of C=C bond; trans = opposite sides)
fat's function
energy storage (stored in adipose cells); adipose tissue also cushions vital organs and insulates the body
phospholipids
two fats and a phosphate group attached to glycerol; fat tail = hydrorphobic. phosphate group & its attachments = hydrophilic; examples: membranes, soaps; when added to water, self-assemble into micelles, liposomes, bilayers; major component of all cell membranes
micelles
polar heads interact with water; nonpolar tails 'hide' inside (looks like little balls with the tails inside)
steroids
lipids characterized by a carbon skeleton consisting of four fused frings
cholesterol
an important steroid, component in animal cell membranes; acts as a precursor molecule for the synthesis of other biologically important steroids, such as hormones
proteins
one or more polypeptides (polymers build from the same set of 20 amino acids); account for more than half of dry mass of most cells
enzymatic proteins
selective acceleration of chemical reactions (ex: digestive enzymes)
structural proteins
support (ex: silk fiber; keratin in hair, horns, feathers and other skin appendages)
storage proteins
storage of amino acids (ex: ovalbumin in egg white)
transport proteins
transport of other substances (ex:hemoglobin, transport proteins)
hormonal proteins
coordination of an organism's activities (ex: insulin)
receptor proteins
response of cell to chemical stimuli (ex: receptors in nerve cells)
contractile and motor proteins
movement (ex: actin and myosin in muscles, proteins in cilia and flagella)
defensive proteins
protection against disease (ex: antibodies combat bacteria and viruses)
aldoses
sugars with the carbonyl group at the end of the carbon chain (aldehyde sugars)
ketoses
sugars with the carbonyl group in the middle of the carbon chain (ketone sugars)
trioses
sugars made of a 3-carbon chain
pentoses
sugars made of a 5-carbon chain
hexoses
sugars made of a 6-carbon chain
criterion for classifying sugars
where the carbonyl group is located (aldehyde sugar vs. ketone sugar); size of the carbon skeleton; spacial arrangement around asymmetric carbons
glucose and cellular respiration
series of reactions start with glucose
importance of simple sugars
energy source for cells; their carbon skeletons are raw material for the synthesis of other types of small organic molecules, such as amino acids and fatty acids; made into disaccharides and polysaccharides
glycosidic linkage
a covalent bond formed between two monosaccharides by a dehydration reactions
actin
A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.
aminopeptidase
An enzyme found within the small intestine that splits off one amino acid at a time, beginning at the opposite end of the polypeptide containing a free carboxyl group.
basal body
A eukaryotic cell organelle consisting of a 9 + 0 arrangement of microtubule triplets; may organize the microtubule assembly of a cilium or flagellum; structurally identical to a centriole.
cell fractionation
The disruption of a cell and separation of its organelles by centrifugation.
cell wall
A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists. In plant cells, the wall is formed of cellulose fibers embedded in a polysaccharide-protein matrix. The primary cell wall is thin and flexible, whereas the secondary cell wall is stronger and more rigid and is the primary constituent of wood.
central vacuole
A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
centriole
A structure in an animal cell composed of cylinders of microtubule triplets arranged in a 9 + 0 pattern. An animal cell usually has a pair of centrioles involved in cell division.
centrosome
Material present in the cytoplasm of all eukaryotic cells, important during cell division; the microtubule-organizing center.
chloroplast
An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
chromatin
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists as a mass of very long, thin fibers that are not visible with a light microscope.
chromosome
A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins. See chromatin.
cilium
A short cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules ensheathed in an extension of plasma membrane.
collagen
A glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom.
contractile vacuole
A membranous sac that helps move excess water out of the cell.
crista
(plural, cristae) An infolding of the inner membrane of a mitochondrion that houses the electron transport chain and the enzyme catalyzing the synthesis of ATP.
cytoplasm
The entire contents of the cell, exclusive of the nucleus, and bounded by the plasma membrane.
cytoplasmic streaming
A circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of materials within cells.
cytoskeleton
A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical and transport functions.
cytosol
The semifluid portion of the cytoplasm.
desmosome
A type of intercellular junction in animal cells that functions as an anchor.
dynein
A large contractile protein forming the side-arms of microtubule doublets in cilia and flagella.
electron microscope (EM)
A microscope that focuses an electron beam through a specimen, resulting in resolving power a thousandfold greater than that of a light microscope. A transmission electron microscope (TEM) is used to study the internal structure of thin sections of cells. A scanning electron microscope (SEM) is used to study the fine details of cell surfaces.
endomembrane system
The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles.
eukaryotic cell
A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles, present in protists, plants, fungi, and animals; also called eukaryote.
extracellular matrix (ECM)
The substance in which animal tissue cells are embedded, consisting of protein and polysaccharides.
fibronectin
A glycoprotein that helps cells attach to the extracellular matrix
flagellum
(plural, flagella) A long cellular appendage specialized for locomotion. The flagella of prokaryotes and eukaryotes differ in both structure and function.
food vacuole
A membranous sac formed by phagocytosis.
gap junction
A type of intercellular junction in animal cells that allows the passage of material or current between cells.
glycoprotein
A protein covalently attached to a carbohydrate.
Golgi apparatus
An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum.
granum
(plural, grana) A stacked portion of the thylakoid membrane in the chloroplast. Grana function in the light reactions of photosynthesis
integrin
A receptor protein built into the plasma membrane that interconnects the extracellular matrix and the cytoskeleton.
intermediate filament
A component of the cytoskeleton that includes all filaments intermediate in size between microtubules and microfilaments.
light microscope (LM)
An optical instrument with lenses that refract (bend) visible light to magnify images of specimens.
lysosome
A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of eukaryotic cells.
microfilament
A solid rod of actin protein in the cytoplasm of almost all eukaryotic cells, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction.
microtubule
A hollow rod of tubulin protein in the cytoplasm of all eukaryotic cells and in cilia, flagella, and the cytoskeleton.
middle lamella
A thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young plant cells.
mitochondrial matrix
The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the Krebs cycle.
mitochondrion
(plural, mitochondria) An organelle in eukaryotic cells that serves as the site of cellular respiration
myosin
A type of protein filament that interacts with actin filaments to cause cell contraction.
nuclear envelope
The membrane in eukaryotes that encloses the nucleus, separating it from the cytoplasm.
nuclear lamina
A netlike array of protein filaments that maintains the shape of the nucleus.
nucleoid
A dense region of DNA in a prokaryotic cell.
nucleolus
(plural, nucleoli) A specialized structure in the nucleus, formed from various chromosomes and active in the synthesis of ribosomes
nucleus
(1) An atom's central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons
organelle
One of several formed bodies with specialized functions, suspended in the cytoplasm of eukaryotic cells.
peroxisome
A microbody containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide.
phagocytosis
A type of endocytosis involving large, particulate substances, accomplished mainly by macrophages, neutrophils, and dendritic cells.
plasma membrane
The membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell's chemical composition.
plasmodesma
(plural, plasmodesmata) An open channel in the cell wall of plant through which strands of cytosol connect from an adjacent cell
plastid
One of a family of closely related plant organelles that includes chloroplasts, chromoplasts, and amyloplasts (leucoplasts).
primary cell wall
A relatively thin and flexible layer first secreted by a young plant cell.
prokaryotic cell
A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea.
proteoglycan
A glycoprotein in the extracellular matrix of animal cells, rich in carbohydrate.
pseudopodium
(plural, pseudopodia) A cellular extension of amoeboid cells used in moving and feeding
ribosome
A cell organelle constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm; consists of rRNA and protein molecules, which make up two subunits.
rough ER
That portion of the endoplasmic reticulum studded with ribosomes.
scanning electron microscope (SEM)
A microscope that uses an electron beam to scan the surface of a sample to study details of its topography.
secondary cell wall
A strong and durable matrix often deposited in several laminated layers for plant cell protection and support.
smooth ER
That portion of the endoplasmic reticulum that is free of ribosomes.
stroma
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
thylakoid
A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
tight junction
A type of intercellular junction in animal cells that prevents the leakage of material between cells.
tonoplast
A membrane that encloses the central vacuole in a plant cell, separating the cytosol from the vacuolar contents, called cell sap; also known as the vacuolar membrane.
transmission electron microscope (TEM)
A microscope that passes an electron beam through very thin sections; primarily used to study the internal ultrastructure of cells.
transport vesicle
A tiny membranous sac in a cell's cytoplasm carrying molecules produced by the cell.
vesicle
A sac made of membrane inside of cells.
active transport
The movement of a substance across a biological membrane against its concentration or electrochemical gradient with the help of energy input and specific transport proteins.
amphipathic molecule
A molecule that has both a hydrophilic region and a hydrophobic region.
aquaporin
A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis).
concentration gradient
An increase or decrease in the density of a chemical substance in an area. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, the ions or other chemical substances involved tend to move from where they are more concentrated to where they are less concentrated.
cotransport
The coupling of the downhilldiffusion of one substance to the uphill transport of another against its own concentration gradient.
diffusion
The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area.
electrochemical gradient
The diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to move relative to the membrane potential.
electrogenic pump
An ion transport protein that generates voltage across a membrane.
endocytosis
The cellular uptake of macromolecules and particulate substances by localized regions of the plasma membrane that surround the substance and pinch off to form an intracellular vesicle.
exocytosis
The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane.
facilitated diffusion
The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients
flaccid
Limp. A walled cell is flaccid in surroundings where there is no tendency for water to enter.
fluid mosaic model
The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids.
gated channel
A protein channel in a cell membrane that opens or closes in response to a particular stimulus.
glycolipid
A lipid covalently attached to a carbohydrate.
glycoprotein
A protein covalently attached to a carbohydrate.
hypertonic
In comparing two solutions, referring to the one with a greater solute concentration.
hypotonic
In comparing two solutions, referring to the one with a lower solute concentration.
integral protein
Typically a transmembrane protein with hydrophobic regions that completely spans the hydrophobic interior of the membrane.
ion channel
Protein channel in a cell membrane that allows passage of a specific ion down its concentration gradient.
isotonic
Having the same solute concentration as another solution.
ligand
A molecule that binds specifically to a receptor site of another molecule.
membrane potential
The charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances.
osmoregulation
The regulation of solute and water concentrations in body fluids by organisms living in hyperosmotic, hypoosmotic, and terrestrial environments.
osmosis
The diffusion of water across a selectively permeable membrane.
passive transport
The diffusion of a substance across a biological membrane.
peripheral protein
A protein appendage loosely bound to the surface of a membrane and not embedded in the lipid bilayer.
phagocytosis
A type of endocytosis involving large, particulate substances, accomplished mainly by macrophages, neutrophils, and dendritic cells.
pinocytosis
A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.
plasmolysis
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment.
proton pump
An active transport mechanism in cell membranes that uses ATP to force hydrogen ions out of a cell, generating a membrane potential in the process.
receptor-mediated endocytosis
The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.
selective permeability
A property of biological membranes that allows some substances to cross more easily than others.
sodium-potassium pump
A special transport protein in the plasma membrane of animal cells that transports sodium out of the cell and potassium into the cell against their concentration gradients.
tonicity
The ability of a solution to cause a cell within it to gain or lose water.
transport protein
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.
turgid
Very firm. A walled cell become turgid if it has a greater solute concentration than its surroundings, resulting in entry of water.
acetyl CoA
Acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme.
aerobic
Containing oxygen; referring to an organism, environment, or cellular process that requires oxygen.
alcohol fermentation
The conversion of pyruvate to carbon dioxide and ethyl alcohol.
anaerobic
Lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen and may be poisoned by it.
ATP synthase
A cluster of several membrane proteins found in the mitochondrial crista (and bacterial plasma membrane) that function in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentration gradient to make ATP. ATP synthases provide a port through which hydrogen ions diffuse into the matrix of a mitrochondrion.
beta oxidation
A metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA.
cellular respiration
The most prevalent and efficient catabolic pathway for the production of ATP, in which oxygen is consumed as a reactant along with the organic fuel.
chemiosmosis
An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most ATP synthesis in cells occurs by chemiosmosis.
citric acid cycle
A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide; occurs within the mitochondrion; the second major stage in cellular respiration.
cytochrome
An iron-containing protein, a component of electron transport chains in mitochondria and chloroplasts.
electron transport chain
A sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.
facultative anaerobe
An organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions.
fermentation
A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.
glycolysis
The splitting of glucose into pyruvate. Glycolysis is the one metabolic pathway that occurs in all living cells, serving as the starting point for fermentation or aerobic respiration.
lactic acid fermentation
The conversion of pyruvate to lactate with no release of carbon dioxide.
NAD+
Nicotinamide adenine dinucleotide, a coenzyme present in all cells that helps enzymes transfer electrons during the redox reactions of metabolism.
oxidation
The loss of electrons from a substance involved in a redox reaction.
oxidative phosphorylation
The production of ATP using energy derived from the redox reactions of an electron transport chain.
oxidizing agent
The electron acceptor in a redox reaction.
proton-motive force
The potential energy stored in the form of an electrochemical gradient, generated by the pumping of hydrogen ions across biological membranes during chemiosmosis.
redox reaction
A chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction.
reducing agent
The electron donor in a redox reaction.
reduction
The addition of electrons to a substance involved in a redox reaction.
substrate-level phosphorylation
The formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism.
activation energy
The amount of energy that reactants must absorb before a chemical reaction will start; also called activation energy.
active site
The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.
allosteric regulation
The binding of a molecule to a protein that affects the function of the protein at a different site.
anabolic pathway
A metabolic pathway that synthesizes a complex molecule from simpler compounds.
ATP (adenosine triphosphate)
An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
bioenergetics
The flow of energy through an animal, taking into account the energy stored in the food it consumes, the energy used for basic functions, activity, growth, reproduction, and regulation, and the energy lost to the environment as heat or in waste.
catabolic pathway
A metabolic pathway that releases energy by breaking down complex molecules to simpler compounds
catalyst
A chemical agent that changes the rate of a reaction without being consumed by the reaction.
chemical energy
Energy stored in the chemical bonds of molecules; a form of potential energy.
coenzyme
An organic molecule serving as a cofactor. Most vitamins function as coenzymes in important metabolic reactions.
cofactor
Any non-protein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely with the substrate during catalysis.
competitive inhibitor
A substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.
cooperativity
An interaction of the constituent subunits of a protein whereby a conformational change in one subunit is transmitted to all the others.
endergonic reaction
A non-spontaneous chemical reaction, in which free energy is absorbed from the surroundings.
energy
The capacity to do work (to move matter against an opposing force).
energy coupling
In cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.
entropy
A quantitative measure of disorder or randomness, symbolized by S.
enzyme
A protein serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction.
enzyme-substrate complex
A temporary complex formed when an enzyme binds to its substrate molecule(s)
exergonic reaction
A spontaneous chemical reaction, in which there is a net release of free energy.
feedback inhibition
A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.
first law of thermodynamics
The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.
free energy
The portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system. The change in free energy of a system is calculated by the equation ΔG = ΔH - T Δs, where T is absolute temperature.
free energy of activation
The amount of energy that reactants must absorb before a chemical reaction will start; also called activation energy.
heat
The total amount of kinetic energy due to molecular motion in a body of matter. Heat is energy in its most random form.
induced fit
The change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by entry of the substrate.
kinetic energy
The energy of motion, which is directly related to the speed of that motion. Moving matter does work by imparting motion to other matter.
metabolic pathway
A series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule into simpler compounds (catabolic pathway).
metabolism
The totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways.
non-competitive inhibitor
A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate.
phosphorylated
Referring to a molecule that has been the recipient of a phosphate group.
potential energy
The energy stored by matter as a result of its location or spatial arrangement.
substrate
The reactant on which an enzyme works.
thermodynamics
(1) The study of energy transformations that occur in a collection of matter. See first law of thermodynamics and second law of thermodynamics. (2) A phenomenon in which external DNA is taken up by a cell and functions there.
absorption spectrum
The range of a pigment's ability to absorb various wavelengths of light.
action spectrum
A graph that depicts the relative effectiveness of different wavelengths of radiation in driving a particular process.
autotroph
An organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones.
bundle-sheath cell
A type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf.
C3 plant
A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate.
C4 plant
A plant that prefaces the Calvin cycle with reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle.
Calvin cycle
The second of two major stages in photosynthesis (following the light reactions), involving atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate.
CAM plant
A plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. Carbon dioxide entering open stomata during the night is converted into organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed.
carbon fixation
The incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic bacterium).
carotenoid
An accessory pigment, either yellow or orange, in the chloroplasts of plants. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis.
chlorophyll
A green pigment located within the chloroplasts of plants. Chlorophyll a can participate directly in the light reactions, which convert solar energy to chemical energy.
chlorophyll a
A type of blue-green photosynthetic pigment that participates directly in the light reactions.
chlorophyll b
A type of yellow-green accessory photosynthetic pigment that transfers energy to chlorophyll a.
crassulacean acid metabolism (CAM)
A type of metabolism in which carbon dioxide is taken in at night and incorporated into a variety of organic acids.
cyclic electron flow
A route of electron flow during the light reactions of photosynthesis that involves only photosystem I and that produces ATP but not NADPH or oxygen.
electromagnetic spectrum
The entire spectrum of radiation ranging in wavelength from less than a nanometer to more than a kilometer.
glyceraldehyde-3-phosphate (G3P)
The carbohydrate produced directly from the Calvin cycle.
heterotroph
An organism that obtains organic food molecules by eating other organisms or their by-products.
light reactions
The steps in photosynthesis that occur on the thylakoid membranes of the chloroplast and that convert solar energy to the chemical energy of ATP and NADPH, evolving oxygen in the process.
light-harvesting complex
Complex of proteins associated with pigment molecules (including chlorophyll a, chlorophyll b, and carotenoids) that captures light energy and transfers it to reaction-outer pigments in a photosystem.
mesophyll
The ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis.
mesophyll cell
A loosely arranged photosynthetic cell located between the bundle sheath and the leaf surface.
NADP+
Nicotinamide adenine dinucleotide phosphate, an acceptor that temporarily stores energized electrons produced during the light reactions.
non-cyclic electron flow
A route of electron flow during the light reactions of photosynthesis that involves both photosystems and produces ATP, NADPH, and oxygen. The net electron flow is from water to NADP+.
PEP carboxylase
An enzyme that adds carbon dioxide to phosphoenolpyruvate (PEP) to form oxaloacetate.
photon
A quantum, or discrete amount, of light energy.
photophosphorylation
The process of generating ATP from ADP and phosphate by means of a proton-motive force generated by the thylakoid membrane of the chloroplast during the light reactions of photosynthesis.
photorespiration
A metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide.
photorespiration
A metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide.
photosynthesis
The conversion of light energy to chemical energy that is stored in glucose or other organic compounds; occurs in plants, algae, and certain prokaryotes.
photosystem
Light-capturing unit located in the thylakoid membrane of the chloroplast, consisting of a reaction center surrounded by numerous light-harvesting complexes. There are two types of photosystems, I and II; they absorb light best at different wavelengths.
photosystem I
One of two light-capturing units in a chloroplast's thylakoid membrane; it has two molecules of P700 chlorophyll a at its reaction center.
photosystem II
One of two light-capturing units in a chloroplast's thylakoid membrane; it has two molecules of P680 chlorophyll a at its reaction center.
primary electron acceptor
A specialized molecule sharing the reaction center with the pair of reaction-center chlorophyll a molecules; it accepts an electron from one of these two chlorophylls.
reaction center
Complex of proteins associated with two special chlorophyll a molecules and a primary electron acceptor. Located centrally in a photosystem, this complex triggers the light reactions of photosynthesis. Excited by light energy, one of the chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain.
rubisco
Ribulose carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP, or ribulose bisphosphate).
spectrophotometer
An instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution.
stoma
A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant.
stroma
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
thylakoid
A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
visible light
That portion of the electromagnetic spectrum detected as various colors by the human eye, ranging in wavelength from about 380 nm to about 750 nm.
wavelength
The distance between crests of waves, such as those of the electromagnetic spectrum.
anaphase
The fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell.
anchorage dependence
The requirement that to divide, a cell must be attached to the substratum.
aster
A radial array of short microtubules that extends from each centrosome toward the plasma membrane in a cell undergoing mitosis.
benign tumor
A mass of abnormal cells that remains at the site of origin.
binary fission
The type of cell division by which prokaryotes reproduce. Each dividing daughter cell receives a copy of the single parental chromosome.
cell cycle
An ordered sequence of events in the life of a eukaryotic cell, from its origin in the division of a parent cell until its own division into two; composed of the M, G1, S, and G2 phases.
cell cycle control system
A cyclically operating set of molecules in the cell that triggers and coordinates key events in the cell cycle.
cell division
The reproduction of cells.
cell plate
A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.
centromere
The centralized region joining two sister chromatids.
checkpoint
A critical control point in the cell cycle where stop and go-ahead signals can regulate the cycle.
chromatin
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, they exist as a mass of very long, thin fibers that are not visible with a light microscope.
chromosome
A threadlike, gene-carrying structure found in the nucleus. Each of these consists of one very long DNA molecule and associated proteins. See chromatin.
cleavage
The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane; specifically, the succession of rapid cell divisions without growth during early embryonic development that converts the zygote into a ball of cells.
cleavage furrow
The first sign of cleavage in an animal cell; a shallow groove in the cell surface near the old metaphase plate.
cyclin
A regulatory protein whose concentration fluctuates cyclically.
cyclin-dependent kinase (Cdk)
A protein kinase that is active only when attached to a particular cyclin.
cytokinesis
The division of the cytoplasm to form two separate daughter cells immediately after mitosis.
density-dependent inhibition
The phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another.
G0 phase
A nondividing state in which a cell has left the cell cycle.
G1 phase
The first growth phase of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.
G2 phase
The second growth phase of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.
gamete
A haploid cell, such as an egg or sperm. These cells unite during sexual reproduction to produce a diploid zygote.
genome
The complete complement of an organism's genes; an organism's genetic material.
growth factor
A protein that must be present in the extracellular environment (culture medium or animal body) for the growth and normal development of certain types of cells; a local regulator that acts on nearby cells to stimulate cell proliferation and differentiation.
interphase
The period in the cell cycle when the cell is not dividing. Cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase. This phase accounts for 90% of the cell cycle.
kinetochore
A specialized region on the centromere that links each sister chromatid to the mitotic spindle.
malignant tumor
A cancerous tumor that is invasive enough to impair the functions of one or more organs.
meiosis
A two-stage type of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell.
metaphase
The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate.
metaphase plate
An imaginary plane during metaphase in which the centromeres of all the duplicated chromosomes are located midway between the two poles.
metastasis
The spread of cancer cells to locations distant from their original site.
mitosis
A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. This process conserves chromosome number by equally allocating replicated chromosomes to each of the daughter nuclei.
mitotic (M) phase
The phase of the cell cycle that includes mitosis and cytokinesis.
mitotic spindle
An assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis.
MPF
Maturation-promoting factor (M-phase-promoting factor); a protein complex required for a cell to progress from late interphase to mitosis. The active form consists of cyclin and a protein kinase.
origin of replication
Site where the replication of a DNA molecule begins.
prometaphase
The second stage of mitosis, in which discrete chromosomes consisting of identical sister chromatids appear, the nuclear envelope fragments, and the spindle microtubules attach to the kinetochores of the chromosomes.
prophase
The first stage of mitosis, in which the chromatin is condensing and the mitotic spindle begins to form, but the nucleolus and nucleus are still intact.
S phase
The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.
sister chromatids
Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II.
somatic cell
Any cell in a multicellular organism except a sperm or egg cell.
telophase
The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun
transformation
(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell.
alternation of generations
A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants.
asexual reproduction
A type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two or more parts.
autosome
A chromosome that is not directly involved in determining sex, as opposed to a sex chromosome.
chiasma
The X-shaped, microscopically visible region representing homologous chromatids that have exchanged genetic material through crossing over during meiosis.
clone
(1) A lineage of genetically identical individuals or cells. (2) In popular usage, a single individual organism that is genetically identical to another individual. (3) As a verb, to make one or more genetic replicas of an individual or cell. See also gene cloning.
crossing over
The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis
diploid cell
A cell containing two sets of chromosomes (2n), one set inherited from each parent.
fertilization
The union of haploid gametes to produce a diploid zygote.
gametophyte
In organisms undergoing alternation of generations, the multicellular haploid form that mitotically produces haploid gametes that unite and grow into the sporophyte generation.
gene
A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).
genetics
The scientific study of heredity and hereditary variation.
haploid cell
A cell containing only one set of chromosomes (n).
heredity
The transmission of traits from one generation to the next
homologous chromosomes
Chromosome pairs of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism's father, the other from the mother.
karyotype
A display of the chromosome pairs of a cell arranged by size and shape.
life cycle
The generation-to-generation sequence of stages in the reproductive history of an organism.
locus
A specific place along the length of a chromosome where a given gene is located.
meiosis
A two-stage type of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell.
meiosis I
The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell.
meiosis II
The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell.
recombinant chromosome
A chromosome created when crossing over combines the DNA from two parents into a single chromosome.
sex chromosome
One of the pair of chromosomes responsible for determining the sex of an individual.
sexual reproduction
A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents.
spore
In the life cycle of a plant or alga undergoing alternation of generations, a meiotically produced haploid cell that divides mitotically, generating a multicellular individual, the gametophyte, without fusing with another cell.
sporophyte
In organisms undergoing alternation of generations, the multicellular diploid form that results from a union of gametes and that meiotically produces haploid spores that grow into the gametophyte generation.
synapsis
The pairing of replicated homologous chromosomes during prophase I of meiosis.
tetrad
A paired set of homologous chromosomes, each composed of two sister chromatids. Tetrads form during prophase I of meiosis.
variation
Differences between members of the same species.
zygote
The diploid product of the union of haploid gametes in conception; a fertilized egg.
alleles
Alternative versions of a gene that produce distinguishable phenotypic effects.
amniocentesis
A technique of prenatal diagnosis in which amniotic fluid, obtained by aspiration from a needle inserted into the uterus, is analyzed to detect certain genetic and congenital defects in the fetus.
carrier
In genetics, an individual who is heterozygous at a given genetic locus, with one normal allele and one potentially harmful recessive allele. The heterozygote is phenotypically normal for the character determined by the gene but can pass on the harmful allele to offspring.
character
An observable heritable feature.
chorionic villus sampling (CVS)
A technique of prenatal diagnosis in which a small sample of the fetal portion of the placenta is removed and analyzed to detect certain genetic and congenital defects in the fetus.
codominance
The situation in which the phenotypes of both alleles are exhibited in the heterozygote.
complete dominance
The situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.
cystic fibrosis
A human genetic disorder caused by a recessive allele for a chloride channel protein; characterized by an excessive secretion of mucus and consequent vulnerability to infection; fatal if untreated.
dihybrid
An organism that is heterozygous with respect to two genes of interest. All the offspring from a cross between parents doubly homozygous for different alleles. For example, parents of genotypes AABB and aabb produce offspring of genotype AaBb.
dominant allele
An allele that is fully expressed in the phenotype of a heterozygote.
epistasis
A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited.
F1 generation
The first filial, or hybrid, offspring in a series of genetic crosses.
F2 generation
Offspring resulting from interbreeding of the hybrid F1 generation.
genotype
The genetic makeup, or set of alleles, of an organism.
heterozygous
Having two different alleles for a given gene.
homozygous
Having two identical alleles for a given gene.
Huntington's disease
A human genetic disease caused by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms.
hybridization
In genetics, the mating, or crossing, of two true-breeding varieties.
incomplete dominance
The situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele.
law of independent assortment
Mendel's second law, stating that each pair of alleles segregates independently during gamete formation; applies when genes for two characters are located on different pairs of homologous chromosomes.
law of segregation
Mendel's first law, stating that each allele in a pair separates into a different gamete during gamete formation.
monohybrid
An organism that is heterozygous with respect to a single gene of interest. All the offspring from a cross between parents homozygous for different alleles are this. For example, parents of genotypes AA and aa produce a offspring of genotype Aa.
multifactorial
Referring to a phenotypic character that is influenced by more than one gene and environmental factors.
norm of reaction
The range of phenotypes produced by a single genotype, due to environmental influences.
P generation
The parent individuals from which offspring are derived in studies of inheritance
pedigree
A diagram of a family tree showing the occurrence of heritable characters in parents and offspring over multiple generations.
phenotype
The physical and physiological traits of an organism, that are determined by its genetic makeup.
pleiotropy
The ability of a single gene to have multiple effects.
polygenic inheritance
An additive effect of two or more gene loci on a single phenotypic character.
Punnett square
A diagram used in the study of inheritance to show the results of random fertilization in genetic crosses.
quantitative character
A heritable feature that varies continuously over a range rather than in an either-or fashion.
recessive allele
An allele whose phenotypic effect is not observed in a heterozygote.
sickle-cell disease
A human genetic disease caused by a recessive allele that results in the substitution of a single amino acid in the hemoglobin protein; characterized by deformed red blood cells that can lead to numerous symptoms.
Tay-Sachs disease
A human genetic disease caused by a recessive allele for a dysfunctional enzyme, leading to accumulation of certain lipids in the brain. Seizures, blindness, and degeneration of motor and mental performance usually become manifest a few months after birth.
testcross
Breeding of an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype. The ratio of phenotypes in the offspring determines the unknown genotype.
trait
Any detectable variation in a genetic character.
true-breeding
Referring to plants that produce offspring of the same variety when they self-pollinate.
aneuploidy
A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number.
Barr body
A dense object lying along the inside of the nuclear envelope in female mammalian cells, representing an inactivated X chromosome.
chromosome theory of inheritance
A basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.
crossing over
The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.
cytologenetic map
Chart of a chromosome that locates genes with respect to chromosomal features.
deletion
(1) A deficiency in a chromosome resulting from the loss of a fragment through breakage. (2) A mutational loss of one or more nucleotide pairs from a gene.
Down syndrome
A human genetic disease caused by presence of an extra chromosome 21; characterized by mental retardation and heart and respiratory defects.
Duchenne muscular dystrophy
A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue.
duplication
An aberration in chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is repeated.
genetic map
An ordered list of genetic loci (genes or other genetic markers) along a chromosome.
genetic recombination
General term for the production of offspring that combine traits of the two parents.
genomic imprinting
Phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent.
hemophilia
A human genetic disease caused by a sex-linked recessive allele; characterized by excessive bleeding following injury
inversion
An aberration in chromosome structure resulting from reattachment in a reverse orientation of a chromosomal fragment to the chromosome from which the fragment originated.
linkage map
A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes.
linked genes
Genes located close enough together on a chromosome to be usually inherited together.
map unit
A unit of measurement of the distance between genes. One map unit is equivalent to a 1% recombination frequency.
monosomic
Referring to a cell that has only one copy of a particular chromosome, instead of the normal two.
nondisjunction
An error in meiosis or mitosis, in which both members of a pair of homologous chromosomes or both sister chromatids fail to move apart properly.
parental type
An offspring with a phenotype that matches one of the parental phenotypes.
polyploidy
A chromosomal alteration in which the organism possesses more than two complete chromosome sets.
recombinant
An offspring whose phenotype differs from that of the parents; also called recombinant type.
sex-linked gene
A gene located on a sex chromosome.
translocation
(1) An aberration in chromosome structure resulting from attachment of a chromosomal fragment to a nonhomologous chromosome. (2) During protein synthesis, the third stage in the elongation cycle when the RNA carrying the growing polypeptide moves from the A site to the P site on the ribosome. (3) The transport of organic nutrients in the phloem of vascular plants.
trisomic
Referring to a cell that has three copies of a particular chromosome, instead of the normal two.
wild type
An individual with the normal (most common) phenotype.
bacteriophage
A virus that infects bacteria; also called a phage.
DNA ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.
DNA polymerase
An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.
double helix
The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.
helicase
An enzyme that untwists the double helix of DNA at the replication forks.
lagging strand
A discontinuously synthesized DNA strand that elongates in a direction away from the replication fork.
leading strand
The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' ( 3' direction.
mismatch repair
The cellular process that uses special enzymes to fix incorrectly paired nucleotides.
nuclease
An enzyme that hydrolyzes DNA and RNA into their component nucleotides.
nucleotide excision repair
The process of removing and then correctly replacing a damaged segment of DNA using the undamaged strand as a guide.
Okazaki fragment
A short segment of DNA synthesized on a template strand during DNA replication. Many Okazaki fragments make up the lagging strand of newly synthesized DNA.
origin of replication
Site where the replication of a DNA molecule begins.
phage
A virus that infects bacteria; also called a bacteriophage.
primase
An enzyme that joins RNA nucleotides to make the primer.
primer
A polynucleotide with a free 3´ end, bound by complementary base pairing to the template strand, that is elongated during DNA replication.
replication fork
A Y-shaped region on a replicating DNA molecule where new strands are growing.
semiconservative model
Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand.
single-strand binding protein
During DNA replication, molecules that line up along the unpaired DNA strands, holding them apart while the DNA strands serve as templates for the synthesis of complementary strands of DNA.
telomerase
An enzyme that catalyzes the lengthening of telomeres. The enzyme includes a molecule of RNA that serves as a template for new telomere segments.
telomere
The protective structure at each end of a eukaryotic chromosome. Specifically, the tandemly repetitive DNA at the end of the chromosome's DNA molecule. See also repetitive DNA.
topoisomerase
A protein that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.
transformation
(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell.
5' cap
The 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide.
A site
One of a ribosome's three binding sites for tRNA during translation. This site holds the tRNA carrying the next amino acid to be added to the polypeptide chain.
alternative RNA splicing
A type of regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.
aminoacyl-tRNA synthetase
An enzyme that joins each amino acid to the correct tRNA.
anticodon
A specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.
base-pair substitution
A type of point mutation; the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides.
codon
A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.
deletion
(1) A deficiency in a chromosome resulting from the loss of a fragment through breakage. (2) A mutational loss of one or more nucleotide pairs from a gene.
domain
(1) A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya. (2) An independently folding part of a protein.
E site
One of a ribosome's three binding sites for tRNA during translation. This site is the place where discharged tRNAs leave the ribosome.
exon
A coding region of a eukaryotic gene. They are separated from each other by introns.
frameshift mutation
A mutation occurring when the number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the following nucleotides into codons.
insertion
A mutation involving the addition of one or more nucleotide pairs to a gene.
intron
A noncoding, intervening sequence within a eukaryotic gene.
mRNA (messenger RNA)
A type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.
missense mutation
The most common type of mutation, a base-pair substitution in which the new codon makes sense in that it still codes for an amino acid.
mutagen
A chemical or physical agent that interacts with DNA and causes a mutation.
mutation
A rare change in the DNA of a gene, ultimately creating genetic diversity.
nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
one gene-one polypeptide hypothesis
The premise that a gene is a segment of DNA that codes for one polypeptide.
P site
One of a ribosome's three binding sites for tRNA during translation. This site holds the tRNA carrying the growing polypeptide chain.
point mutation
A change in a gene at a single nucleotide pair.
poly-A tail
The modified end of the 3' end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides.
polyribosome (polysome)
An aggregation of several ribosomes attached to one messenger RNA molecule.
primary transcript
An initial RNA transcript; also called pre-mRNA when transcribed from a protein-coding gene.
promoter
A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA.
reading frame
The way a cell's mRNA-translating machinery groups the mRNA nucleotides into codons.
rRNA (ribosomal RNA)
The most abundant type of RNA, which together with proteins forms the structure of ribosomes.
ribosome
A cell organelle constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm; consists of rRNA and protein molecules, which make up two subunits.
ribozyme
An enzymatic RNA molecule that catalyzes reactions during RNA splicing.
RNA polymerase
An enzyme that links together the growing chain of ribonucleotides during transcription.
RNA processing
Modification of RNA before it leaves the nucleus, a process unique to eukaryotes.
RNA splicing
The removal of noncoding portions (introns) of the RNA molecule after initial synthesis.
signal peptide
A stretch of amino acids on a polypeptide that targets the protein to a specific destination in a eukaryotic cell.
signal-recognition particle (SRP)
A protein-RNA complex that recognizes a signal peptide as it emerges from the ribosome.
spliceosome
A complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron and joining the two adjacent exons.
TATA box
A promoter DNA sequence crucial in forming the transcription initiation complex.
template strand
The DNA strand that provides the template for ordering the sequence of nucleotides in an RNA transcript.
terminator
In prokaryotes, a special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene.
transcription
The synthesis of RNA on a DNA template.
transcription factor
A regulatory protein that binds to DNA and stimulates transcription of specific genes.
transcription initiation complex
The completed assembly of transcription factors and RNA polymerase bound to the promoter.
transcription unit
A region of a DNA molecule that is transcribed into an RNA molecule.
tRNA (transfer RNA)
An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA.
translation
The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of languagefrom nucleotides to amino acids.
triplet code
A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.
wobble
A violation of the base-pairing rules in that the third nucleotide (5' end) of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon.
activator
A protein that binds to DNA and stimulates transcription of a specific gene.
AIDS (acquired immunodeficiency syndrome)
The name of the late stages of HIV infection, defined by a specified reduction of T cells and the appearance of characteristic secondary infections.
bacteriophage
A virus that infects bacteria; also called a phage.
capsid
The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex in shape.
conjugation
In prokaryotes, the direct transfer of DNA between two cells that are temporarily joined. In ciliates, a sexual process in which two cells exchange haploid micronuclei.
corepressor
A small molecule that cooperates with a repressor protein to switch on operon off.
cyclic AMP (cAMP)
Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells (for example, in vertebrate endocrine cells). It is also a regulator of some bacterial operons.
episome
A genetic element that can exist either as a plasmid or as part of the bacterial chromosome.
F factor
A fertility factor in bacteria; a DNA segment that confers the ability to form pili for conjugation and associated functions required for the transfer of DNA from donor to recipient. It may exist as a plasmid or be integrated into the bacterial chromosome.
F plasmid
The plasmid form of the F factor.
HIV (human immunodeficiency virus)
The infectious agent that causes AIDS. It is a retrovirus.
host range
The limited range of host cells that each type of virus can infect and parasitize.
inducer
A specific small molecule that inactivates the repressor in an operon.
insertion sequence
The simplest kind of transposable element, consisting of inverted repeats of DNA flanking a gene for transposase, the enzyme that catalyzes transposition.
lysogenic cycle
A phage replication cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host.
lytic cycle
A type of viral (phage) replication cycle resulting in the release of new phages by lysis (and death) of the host cell.
nucleoid
A dense region of DNA in a prokaryotic cell.
operator
In prokaryotic DNA, a sequence of nucleotides near the start of an operon to which an active repressor can attach. The binding of the repressor prevents RNA polymerase from attaching to the promoter and transcribing the genes of the operon.
operon
A unit of genetic function common in bacteria and phages, consisting of coordinately regulated clusters of genes with related functions.
phage
A virus that infects bacteria; also called a bacteriophage.
plasmid
A small ring of DNA that carries accessory genes separate from those of a bacterial chromosome; also found in some eukaryotes, such as yeast.
prion
An infectious form of protein that may increase in number by converting related proteins to more prions.
prophage
A phage genome that has been inserted into a specific site on the bacterial chromosome.
provirus
Viral DNA that inserts into a host genome.
R plasmid
A bacterial plasmid carrying genes that confer resistance to certain antibiotics.
regulatory gene
A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.
repressor
A protein that suppresses the transcription of a gene.
retrovirus
An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.
reverse transcriptase
An enzyme encoded by some certain viruses (retroviruses) that uses RNA as a template for DNA synthesis.
temperate phage
A phage that is capable of reproducing by either the lytic or lysogenic cycle.
transduction (1)
A DNA transfer process in which phages carry bacterial genes from one host cell to another. (2) In cellular communication, the conversion of a signal from outside the cell to a form that can bring about a specific cellular response.
transformation
(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell.
transposable genetic element
A segment of DNA that can move within the genome of a cell by means of a DNA or RNA intermediate.
transposon
A transposable genetic element that moves within a genome by means of a DNA intermediate.
vaccine
A harmless variant or derivative of a pathogen that stimulates a host's immune system to mount defenses against the pathogen.
viral envelope
A membrane that cloaks the capsid that in turn encloses a viral genome.
viroid
A plant pathogen composed of molecules of naked circular RNA only several hundred nucleotides long.
virulent phage
A phage that reproduces only by a lytic cycle.
activator
A protein that binds to DNA and stimulates transcription of a specific gene.
alternative RNA splicing
A type of regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.
cell differentiation
The structural and functional divergence of cells as they become specialized during a multicellular organism's development; dependent on the control of gene expression.
chromatin
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, this complex exists as a mass of very long, thin fibers that are not visible with a light microscope.
control element
A segment of noncoding DNA that helps regulate transcription of a gene by binding proteins called transcription factors.
differential gene expression
The expression of different sets of genes by cells with the same genome.
enhancer
A DNA segment containing multiple control elements that may be located far away from the gene it regulates.
epigenetic inheritance
Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence.
euchromatin
The more open, unraveled form of eukaryotic chromatin that is available for transcription.
genomic imprinting
Phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent.
heterochromatin
Nontranscribed eukaryotic chromatin that is so highly compacted that it is visible with a light microscope during interphase.
histone
A small protein with a high proportion of positively charged amino acids that binds to the negatively charged DNA and plays a key role in its chromatin structure.
histone acetylation
The attachment of acetyl groups to certain amino acids of histone proteins.
micro-RNA (miRNA)
A small, single-stranded RNA molecule that binds to a complementary sequence in mRNA molecules and directs associated proteins to degrade or prevent translation of the target mRNA.
multigene family
A collection of genes with similar or identical sequences, presumably of common origin.
nucleosome
The basic, bead-like unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a protein core composed of two copies of each of four types of histone.
oncogene
A gene found in viruses or as part of the normal genome that is involved in triggering cancerous characteristics.
p53 gene
The guardian angel of the genome, a gene that is expressed when a cell's DNA is damaged. Its product, a protein, functions as a transcription factor for several genes.
proteasome
A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin.
proto-oncogene
A normal cellular gene corresponding to an oncogene; a gene with a potential to cause cancer but that requires some alteration to become an oncogene.
pseudogene
A DNA segment very similar to a real gene but which does not yield a functional product; a gene that has become inactivated in a particular species because of mutation.
Ras gene
A gene that codes for a protein of the same name, a G protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases that ultimately results in the stimulation of the cell cycle. Many oncogenes of the same name have a point mutation that leads to a hyperactive version of this type of protein that can lead to excessive cell division.
repetitive DNA
Nucleotide sequences, usually noncoding, that are present in many copies in a eukaryotic genome. The repeated units may be short and arranged tandemly (in series) or long and dispersed in the genome.
repressor
A protein that suppresses the transcription of a gene.
retrotransposon
A transposable element that moves within a genome by means of an RNA intermediate, a transcript of the retrotransposon DNA.
RNA interference (RNAi)
A technique to silence the expression of selected genes in nonmammalian organisms. The method uses synthetic double-stranded RNA molecules matching the sequence of a particular gene to trigger the breakdown of the gene's messenger RNA.
transcription factor
A regulatory protein that binds to DNA and stimulates transcription of specific genes.
transposon
A transposable genetic element that moves within a genome by means of a DNA intermediate.
tumor-suppressor gene
A gene whose protein products inhibit cell division, thereby preventing uncontrolled cell growth (cancer).
physiology
study of biological functions organism performs
anatomy
study of biological form of an organism
evolutionary convergence
reflects different species' adaptations to similar environmental challenge
interstitial fluid
fills space between cells, allows for movement of material into & out of cells
Epithelial Tissue
covers outside of body & lines organs & cavities w/in body
columnar
The column shape of a type of epithelial cell.
cuboidal
The cubic shape of a type of epithelial cell.
squamous
The flat, tile-like shape of a type of epithelial cell.
stratified epithelium
An epithelium consisting of more than one layer of cells in which some but not all cells touch the basal lamina.
simple epithelium
An epithelium consisting of a single layer of cells that all touch the basal lamina.
Muscle Tissue
Tissue consisting of long muscle cells that are capable of contracting when stimulated by nerve impulses.
skeletal muscle (striated muscle)
Muscle generally responsible for the voluntary movements of the body.
smooth muscle
A type of muscle lacking the striations of skeletal and cardiac muscle because of the uniform distribution of myosin filaments in the cell.
cardiac muscle
A type of muscle that forms the contractile wall of the heart. Its cells are joined by intercalated discs that relay each heartbeat.
nervous tissue
Tissue made up of neurons and supportive cells.
neuron
A nerve cell; the fundamental unit of the nervous system, having structure and properties that allow it to conduct signals by taking advantage of the electrical charge across its cell membrane.
glial cells
help nourish, insulate & replenish neurons (support cells)
endocrine system
transmits chemical signals called hormones to receptive cells throughout the body via blood
hormones
are relatively slow acting, but can have long-lasting effects
connective tissue
Animal tissue that functions mainly to bind and support other tissues, having a sparse population of cells scattered through an extracellular matrix.
loose connective tissue
The most widespread connective tissue in the vertebrate body. It binds epithelia to underlying tissues and functions as packing material, holding organs in place.
fibrous connective tissue
A dense tissue with large numbers of collagenous fibers organized into parallel bundles. This is the dominant tissue in tendons and ligaments.
cartilage
A type of flexible connective tissue with an abundance of collagenous fibers embedded in chondroitin.
bone
A type of connective tissue, consisting of living cells held in a rigid matrix of collagen fibers embedded in calcium salts.
blood
A type of connective tissue with a fluid matrix called plasma in which blood cells are suspended.
preformation
18th century theory that egg or sperm contains miniature infant (homunculus) which becomes larger during development
cytoplasmic determinants
The maternal substances in the egg that influence the course of early development by regulating the expression of genes that affect the developmental fate of cells.
cell differentiation
The structural and functional divergence of cells as they become specialized during a multicellular organism's development; dependent on the control of gene expression.
morphogenesis
The development of body shape and organization.
model organisms
species that are representative of a larger group & easily studied
cleavage
The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane; specifically, the succession of rapid cell divisions without growth during early embryonic development that converts the zygote into a ball of cells.
blastula
The hollow ball of cells marking the end stage of cleavage during early embryonic development.
gastrulation
Cells are rearranged into 3 distinct layers
organogenesis
The development of organ rudiments from the three germ layers.
acrosomal reaction
The discharge of a sperm's acrosome when the sperm approaches an egg.
acrosome
A vesicle at the tip of a sperm cell that helps the sperm penetrate the egg.
fast block to polyspermy
The depolarization of the egg membrane within 1-3 seconds after sperm binding to the vitelline layer. The reaction prevents additional sperm from fusing with the egg's plasma membrane.
cortical reaction
Exocytosis of enzymes from cortical granules in the egg cytoplasm during fertilization.
slow block to polyspermy
The formation of the fertilization envelope and other changes in the egg's surface that prevent fusion of the egg with more than one sperm.
blastomere
A small cell of an early embryo.
blastocoel
The fluid-filled cavity that forms in the center of the blastula embryo.
Embryo Polarity
eggs & zygotes of many animals, except mammals, have a definite polarity (distribution of the yolk)
vegetal pole
The portion of the egg where most yolk is concentrated; opposite of animal pole.
animal pole
The portion of the egg where the least yolk is concentrated; opposite of vegetal pole.
gastrula
a three-layered structure that has a primitive gut
germ layers
Three main layers that form the various tissues and organs of an animal body.
ectoderm
The outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye.
endoderm
The innermost of the three primary germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract.
mesoderm
The middle primary germ layer of an early embryo that develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, kidneys, and most of the circulatory system.
amniote
Member of a clade of tetrapods that have an amniotic egg containing specialized membranes that protect the embryo, including mammals and birds and other reptiles.
transformation
uptake & expression of foreign DNA
transduction
new genes tag along with f DNA
conjugation
bacteria trade plasmids
plasmid
small circular DNA w/ 1 or a few genes
F plasmid
cells that contain this function as DNA donors during conjugation; F+ cells transfer DNA to F- recipients; chromosomal genes can be transferred during conjugation when donor cell's F factor is integrated into chromosome
Hfr cell
cell w/ built-in F factor; F factor of this type of cell brings some chromosomal DNA along when transferred to F- cell
R plasmids
confer resistance to various antibiotics
transposable elements
"jumping genes" - contribute to genetic shuffling in bacteria
insertion sequences
simplest transposable elements, exist only in bacteria; has single gene for transposase, an enzyme catalyzing movement of the insertion sequence from one site to another w/in genome
transposons
transposons have DNA required for transposition & extra genes that "go along for the ride" such as genes for antibiotic resistance
genetic engineering
direct manipulation of genes for practical purposes
biotechnology
manipulation of organisms or their genetic components to make useful products
DNA cloning/molecular cloning
yields multiple copies of a gene or other DNA segment
gene cloning
using bacteria to make multiple copies of a gene
restriction enzymes
cut DNA molecules @ specific DNA sequences
restriction sites
A specific sequence on a DNA strand that is recognized as a cut siteby a restriction enzyme.
restriction fragment
DNA segment resulting from cutting of DNA by a restriction enzyme.
sticky end
A single-stranded end of a double-stranded DNA restriction fragment.
cloning vector
DNA molecule that can carry foreign DNA into host cell & replicate there
genomic library
collection of recombinant vector clones produced by cloning DNA fragments from an entire genome
expression vector
a cloning vector that contains a highly active prokaryotic promoter that helps expression of cloned eukaryotic genes in bacterial host cells
Eukaryotic Cloning and Expression Systems
use of cultured eukaryotic cells as host cells & yeast artificial chromosomes (YACs) as vectors helps avoid gene expression problems YACs behave normally in mitosis & can carry more DNA than a plasmid eukaryotic hosts can provide the post-translational modifications that many proteins require
PCR (Polymerase Chain Reaction )
can produce many copies of a specific target segment of DNA
gel electrophoresis
The separation of nucleic acids or proteins, on the basis of their size and electrical charge, by measuring their rate of movement through an electrical field in a gel.
Southern blotting
A hybridization technique that enables researchers to determine the presence of certain nucleotide sequences in a sample of DNA.
restriction fragment analysis
DNA fragments produced by restriction enzyme digestion of DNA molecule are sorted by gel electrophoresis
Northern blotting
combines gel electrophoresis of mRNA followed by hybridization with a probe on a membrane
Reverse transcriptase-polymerase chain reaction (RT-PCR)
is a laboratory technique for amplifying a defined piece of a ribonucleic acid (RNA) molecule. The RNA strand is first reverse transcribed into its DNA complement or complementary DNA, followed by amplification of the resulting DNA using polymerase chain reaction
in situ hybridization
uses fluorescent dyes attached to probes to identify location of specific mRNAs in place in intact organism
DNA microarrays
A method to detect and measure the expression of thousands of genes at one time. Tiny amounts of a large number of single-stranded DNA fragments representing different genes are fixed to a glass slide. These fragments, ideally representing all the genes of an organism, are tested for hybridization with various samples of cDNA molecules.
nuclear transplantation
nucleus of unfertilized egg cell or zygote replaced w/ nucleus of a differentiated cell
stem cell
relatively unspecialized cell that can reproduce itself indefinitely & differentiate into specialized cells of one or more types
embryonic stem cells
SCs isolated from early embryos @ blastocyst stage. They are pluripotent
pluripotent
able to differentiate into all cell types except extraembryonic tissues
multipotent
replace nonreproducing specialized cells
single nucleotide polymorphisms (SNPs)
single base-pair sites that vary in a population
restriction fragment length polymorphism (RFLP)
Differences in DNA sequence on homologous chromosomes that can result in different patterns of restriction fragment lengths (DNA segments resulting from treatment with restriction enzymes); useful as genetic markers for making linkage maps.
gene therapy
alteration of an afflicted individual's genes
Potential Medical Issues of gene therapy
immune responses; risk of inducing cancer
cytoplasmic determinants
zygote's genome & molecules in egg
cell differentiation
specialization of cells in structure & function
morphogenesis
process by which animal takes shape
cleavage
cell division creates hollow ball of cells (a "blastula")
gastrulation
cells are rearranged into 3 distinct layers
organogenesis
three layers interact & move to give rise to organs
acrosomal reaction
The discharge of hydrolytic enzymes from the acrosome, a vesicle in the tip of a sperm, when the sperm approaches or contacts an egg.
acrosome
A vesicle in the tip of a sperm containing hydrolytic enzymes and other proteins that help the sperm reach the egg.
inner cell mass
develops into embryo & forms extraembryonic membranes
trophoblast
outer epithelium of blastocyst, initiates implantation in uterus
convergent extension
A process in which the cells of a tissue layer rearrange themselves, so that the sheet of cells becomes narrower (converges) and longer (extends).
fate maps
general territorial diagrams of embryonic development
totipotent
Describing a cell that can give rise to all parts of the embryo and adult, as well as extraembryonic membranes in species that have them.
induction
The process in which one group of embryonic cells influences the development of another, usually by causing changes in gene expression.
pattern formation
The development of a multicellular organism's spatial organization, the arrangement of organs and tissues in their characteristic places in three-dimensional space.
apical ectodermal ridge (AER)
one limb-bud organizer region; thickened ectoderm @ tip of limb bud
zone of polarizing activity (ZPA)
mesodermal tissue under ectoderm where posterior side of limb bud is attached to body
sexual reproduction
creation of offspring by fusion of male gamete (sperm) & female gamete (egg) to form zygote
asexual reproduction
creation of offspring w/o gamete fusion
fission
separation of parent into 2 or more individuals of about same size (ex - bacteria, yeast)
budding
new individuals arise from outgrowths of existing ones (ex - hydra)
fragmentation
breaking of body into pieces, some or all of which develop into adults (ex - starfish)
parthenogenesis
development of new individual from unfertilized egg (ex - Komodo Dragons)
ovulation
release of mature eggs @ midpoint of female cycle; expels egg cell from follicle & ovary, into fallopian tubes
fertilization
union of egg & sperm
external fertilization
eggs shed by female are fertilized by sperm in external environment
internal fertilization
sperm are deposited in/near female reproductive tract & fertilization occurs w/in tract; requires behavioral interactions & compatible copulatory organs
gonads
organs that produce gametes
Vulva
external genitalia, includes Labia majora, Labia minora and Clitoris
female internal genitalia
Vagina, Cervix, and Uterus
endometrium
inner layer of (stratified, squamous, nonkeratinized) epithelium shed during menstruation
Fallopian (uterine) tubes
ova is drawn into the tubes by cilia; egg uses this to travel from ovary to uterus
Ovaries
female gonads, lie in abdominal cavity, large number of follicles which enclose ova, also secrete hormones
oocyte
partially developed egg
oogenesis
The process in the ovary that results in the production of female gametes.
corpus luteum
A secreting tissue in the ovary that forms from the collapsed follicle after ovulation and produces progesterone.
endometrium
The inner lining of the uterus, which is richly supplied with blood vessels.
male external genitalia
testes and penis
male internal genitalia
seminal vesicles, Cowper's glands, prostate gland, epididymis & vas deferens
testes
The male reproductive organ, or gonad, in which sperm and reproductive hormones are produced.
seminiferous tubules
A highly coiled tube in the testis in which sperm are produced
Leydig cells
A cell that produces testosterone and other androgens and is located between the seminiferous tubules of the testes.
gametogenesis
The process by which gametes are produced in the mammalian body.
spermatogenesis
The continuous and prolific production of mature sperm cells in the testis.
oogenesis
development of mature oocytes (eggs)
menstruation
The shedding of portions of the endometrium, a reoccurring event.
menstrual cycle
In higher primates, a type of reproductive cycle in which the nonpregnant endometrium is shed as a fluid discharge through the cervix into the vagina.
ovarian cycle
The cyclic recurrence of the follicular phase, ovulation, and the luteal phase in the mammalian ovary, regulated by hormones.
Estrous Cycle
A reproductive cycle characteristic of female mammals except higher primates, in which the nonpregnant endometrium is reabsorbed rather than shed, and sexual response occurs only during mid-cycle at estrus.
ectopic pregnancy
Pregnancy occurring in an abnormal location.