a subatomic particle with a single negative charge; one or more electrons move around the nucleus
one of several atomic forms of an element each containing different number of neutrons and different in atomic mass
an attraction between two atoms resulting from a sharing of outer shell electrons or the presence of opposite charges on the atom; the bonded atoms gain compounds outer electron shells
a type of strong chemical bond in which two atoms share one pair of valence electrons
polar covalent bonds
a type of covalent bond between atoms that differ in electronegativity. the shared electrons are pulled closer to the more electronegative atom. making one slightly negative and the other slightly positive
a type of weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecules is attracted to the slightly negative atom of a polar covalent in another bond
total amount of kinetic energy due to molecular motion in a body of matter. It is energy in most random form
a measure of the intensity of heat in degrees reflecting molecules average kinetic energy
the amount of heat that must be absorbed lost for one gram of a substance to change its temperature by one degree
A substance that consists of acid and base forms in a solution and that minimizes changes in pH when extraneous acids or bases are added to the solution.
One of several organic compounds with the same molecular formula but different structures and therefore different properties. The three types are structural , geometric and enantiomers.
Compounds that have the same molecular formula but differ in the covalent arrangements of their atoms.
Compounds that have the same molecular formula but differ in the spatial arrangements of their atoms.
A specific configuration of atoms commonly attached to the carbon skeletons of organic molecules and usually involved in chemical reactions.
A functional group consisting of a hydrogen atom joined to an oxygen atom by a polar covalent bond. Molecules possessing this group are soluble in water and are called alcohols.
A functional group present in aldehydes and ketones and consisting of a carbon atom double-bonded to an oxygen atom.
An organic compound with a carbonyl group of which the carbon atom is bonded to two other carbons.
A functional group present in organic acids and consisting of a single carbon atom double-bonded to an oxygen atom and also bonded to a hydroxyl group.
A functional group that consists of a nitrogen atom bonded to two hydrogen atoms; can act as a base in solution, accepting a hydrogen ion and acquiring a charge of +1.
A giant molecule formed by the joining of smaller molecules, usually by a condensation reaction. Polysaccharides, proteins, and nucleic acids are macromolecules.
A reaction in which two molecules become covalently bonded to each other through the loss of a small molecule, usually water; also called dehydration reaction.
A chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule.
A chemical process that lyses, or splits, molecules by the addition of water; an essential process in digestion.
A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides).
The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides. Also known as simple sugars, the molecular formulas of are generally some multiple of CH2O.
An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch.
A structural polysaccharide of cell walls, consisting of glucose monomers joined by b-1, 4-glycosidic linkages.
A long carbon chain carboxylic acid. vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form fat.
saturated fatty acid
A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that can attach to the carbon skeleton.
unsaturated fatty acid
A fatty acid possessing one or more double bonds between the carbons in the hydrocarbon tail. Such bonding reduces the number of hydrogen atoms attached to the carbon skeleton.
A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.
A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.
A type of lipid characterized by a carbon skeleton consisting of four rings with various functional groups attached.
A polymer of up to over a thousand monosaccharides, formed by dehydration reactions.
An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of proteins.
A three-dimensional biological polymer constructed from a set of 20 different monomers called amino acids.
beta (B) pleated sheet
One form of the secondary structure of proteins in which the polypeptide chain folds back and forth, or where two regions of the chain lie parallel to each other and are held together by hydrogen bonds.
For proteins, a process in which a protein unravels and loses its native conformation, thereby becoming biologically inactive. For DNA, the separation of the two strands of the double helix. Denaturation occurs under extreme conditions of pH, salt concentration, and temperature.
A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis and as the genome of some viruses.
A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell's proteins.
A polymer (polynucleotide) consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.
One of two families of nitrogenous bases found in nucleotides. Adenine (A) and guanine (G) are purines.
One of two families of nitrogenous bases found in nucleotides. Cytosine (C), thymine (T), and uracil (U) are pyrimidines.
One of several formed bodies with specialized functions, suspended in the cytoplasm of eukaryotic cells.
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.
A machine that spins test tubes at the fastest speeds to separate liquids and particles of different densities.
A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea.
The entire contents of the cell, exclusive of the nucleus, and bounded by the plasma membrane.
The membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell's chemical composition.
(1) An atom's central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons.
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing,exists as a mass of very long, thin fibers that are not visible with a light microscope.
One of a family of closely related plant organelles, including chloroplasts, chromoplasts, and amyloplasts (leucoplasts).
A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
A membrane that encloses the central vacuole in a plant cell, separating the cytosol from the cell sap
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.
(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.
A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
A stacked portion of the thylakoid membrane in the chloroplast. Grana function in the light reactions of photosynthesis
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
A microbody containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide.
A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical and transport functions.
Material present in the cytoplasm of all eukaryotic cells, important during cell division; the microtubule-organizing center.
A long 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.
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.
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.
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.
The substance in which animal tissue cells are embedded consisting of protein and polysaccharides.
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.
A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins.
A specialized structure in the nucleus, formed from various chromosomes and active in the synthesis of ribosomes.
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
An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.
An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum.
A tiny membranous sac in a cell's cytoplasm carrying molecules produced by the cell.
(the ability to allow some sub. to cross the plasma membrane more easily) A property of biological membranes that allows some substances to cross more easily than others.
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.
Typically transmembrane proteins with hydrophobic regions that completely span the hydrophobic interior of the membrane.
Protein appendages loosely bound to the surface of the membrane and not embedded in the lipid bilayer.
The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area.
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
The control of water balance in organisms living in hypertonic, hypotonic, or terrestrial environments.
Firm. Walled cells become turgid as a result of the entry of water from a hypotonic environment.
Limp. Walled cells are limp in isotonic surroundings, where there is no tendency for water to enter.
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
The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients
(water channel proteins that facilitate the amount of diffusion)A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis).
A protein channel in a cell membrane that opens or closes in response to a particular stimulus.
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.
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.
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.
An active transport mechanism in cell membranes that consumes ATP to force hydrogen ions out of a cell and, in the process, generates a membrane potential
The coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient.
The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane.
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.
A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.
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.
chromatin, nucleolus, nuclear envelope--> directs protein synthesis by synthesizing RNA (mRNA) and sending it to the cytoplasm via nuclear pores-->the mRNA is made according to instruction provided by DNA --> mRNA reaches cytoplasm ribosomes translate the genetic message into polypeptide
specialized structure in special type of RNA, ribosomal RNA, is synthesized + assembled w/ proteins imported from cytoplasm into main components of ribsomal subunits which pass nuclear portes to cytoplasm where they combine to form ribosomes
double membrane perforated by pores which regulate entry and exit of certain macromolecules and particles
attached to outside of ER or nuclear envelope- proteins that are destined for insertion into membranes or packaging certain organelles (ex: lysosome)
network of membrane sacs and tubes; active in membrane synthesis and other synthetic and metabolic processes
synthesis of lipids, phospholipids and steroid sex hormones-help detoxify drugs and poisons (liver cells) involves adding hydroxyl groups to drugs to make soluble and easier to flush from body
sythesis of secretory proteins (glycoproteins) specialized cells secrete proteins produced by rough ER ribosomes and membrane production
center of manufacturing, warehousing, sorting, and shipping products are usually modified during their transit from the cis pole to the trans pole
golgi appartus--> usually located near the ER a vesicle that buds from the ER will add its membrane and the contents of its lumen,cavity, to this face
digestive compartments (macromolecules) carry out intracellular digestion . Use their hydrolytic enzymes to recycle the cell's own organic material (autophagy)
sites of cellular respiration the catbolic process that generates ATP by extracting energy from sugars, fats + other fuels w/ oxygens help
sites of photosynthesis. convert solar energy--> chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds from CO2 and H20
generate and degrade H2O2 in performing various metabolic functions transfer hydrogen from various substrates to oxygen and they produce H2O2. Use O to break fatty acids that can be sent to mitochondria
maintenance of cell shape (compression resisting girders) cell motility organelle and chromosome movement
anchorage of nucleus and certain other organelles, formation of nuclear lamina
function in support, adhesion, movement, and regulation (glycoproteins) collagen most abundant in animal cells
membranes of neighboring cells are actually fused forming continuous belts around cell to prevent leakage of extracellular fluid
function like rivets fastening cells together into strong sheets Intermediate filaments reinforce this
Amphipathic molecules have both hydrophobic regions and hydrophilic regions <phospholipids>.
fluid mosaic model
The arrangement of phospholipids and proteins in biological membranes is described by the
splits a membrane along the middle of the phospholipid bilayer. When a freeze-fracture preparation is viewed with an electron microscope, protein particles are interspersed in a smooth matrix, supporting the fluid mosaic model.
are not embedded in the lipid bilayer at all. Instead, the are loosely bound to the surface of the protein, often connected to integral proteins
penetrate the hydrophobic core of the lipid bilayer, often completely spanning the membrane (as transmembrane proteins).
functions of the proteins
1. Transport of specific solutes into or out of cells. 2. Enzymatic activity, sometimes catalyzing one of a number of steps of a metabolic pathway 3. Signal transduction, relaying hormonal messages to the cell. 4. Cell-cell recognition, allowing other proteins to attach two adjacent cells together 5. Intercellular joining of adjacent cells with gap or tight junctions 6. Attachment to the cytoskeleton and extracellular matrix, maintaining cell shape and stabilizing the location of certain membrane proteins.
the ability of a cell to distinguish one type of neighboring cell from another is crucial to the functioning of an organism carbohydrates are important for this
span the membrane 1. channel proteins which have a hydrophilic channel that certain molecules or ions can use as a tunnel through the membrane (aquaporins facilitate the passage of water through the membrane) 2. carrier proteins bind to molecules and change shape to shuttle them across the membrane
the tendency of molecules of any substance to spread out in the available space it is driven by intrinsic kinetic energy (thermal motion or heat) of molecules
the diffusion of a substance across a biological membrane because it require no energy from the cell to make it happen - the concentration gradient represents potential energy and drives fusion
an increase or decrease in the density of a chemical substance in an area -->substances tend to move form where there are more concentrated to where they are less concentrated
the passive transport of water; diffusion of water across a selectively permeable membrane; the direction of osmosis is determined only by a difference in total solute concentration ; the kind of solutes in the solution do not matter
the passive movement of molecules down their concentration gradient via transport proteins
many ion channels function as gated channels these channels open or close depending on the presence or absence of a chemical or physical stimulus
uses energy to move solutes against their gradients; requires the cell to expend metabolic energy; enables a cell to maintain its internal concentrations of small molecules that would otherwise diffuse across he membrane ; ATP supplies the energy for active transport
ATP can power active transport by transferring a phosphate group from ATP to the transport protein. This may induce a conformation change in the transport proteins translocating the solute across the membrane
sodium potassium pump
actively maintains the gradient of sodium ions (Na+) and potassium ions (K+) across the plasma membrane of animal cells . K+ concentration is low outside animal cell and high inside the cell. Na+ concentration is high outside an animal cell and low inside the cell. the sodium potassium pump maintains these concentration gradients using the energy of one ATP to pump three Na+ out and two K+ in
voltage across a membrane. ranges from -50 to -200 millivolts. inside of cell negative compared to the outside
drive the diffusion of ions across a membrane 1. chemical force based on an ions concentration gradient. 2. the other is an electrical force based on the effect of the membrane potential on the ion's movement ion diffuses down its electrochemical gradient
special transport proteins that generate the voltage gradient across a membrane an example is the Na+-K+ pump restores the electrochemical gradient not only by the active transport of Na+ and K+ setting up a concentration gradien but because it pumps 2 K+ for every 3 Na+ setting up a voltage across membrane
in plants bacteria and fungi it is the major electrogenic pump actively transporting H+ out of the cell
a single ATP powered pump that transports one solute can indirectly drive the active transport of several other solutes in this mechanism as the solute that has been actively transported diffuses back passively through a transport protein its movement can be coupled with the active transport of another substance against its concentration gradient
the cell engulfs a particle by extending psedopodia around it and packaging it in a large vacuole
(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.
1st law of thermodynamics
The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.
2nd law of thermodynamics
The principle whereby every energy transfer or transformation increases the entropy of the universe. Ordered forms of energy are at least partly converted to heat, and in spontaneous reactions, the free energy of the system also decreases.
The portion of a system's energy that can perform work when temperature is uniform throughout the system.
A nonspontaneous chemical reaction in which free energy is absorbed from the surroundings
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.
In cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.
A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.
A chemical agent that changes the rate of a reaction without being consumed by the reaction.
The amount of energy that reactants must absorb before a chemical reaction will start.
A substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.
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.
The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.
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.
Any nonprotein molecule or ion that is required for the proper functioning of an enzyme can be permanently bound to the active site or may bind loosely with the substrate during catalysis.
An organic molecule serving as a cofactor. Most vitamins function in important metabolic reactions.
A specific receptor site on some part of an enzyme molecule remote from the active site.
A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.
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.
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.
A chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction
a coenzyme present in all cells that helps enzymes transfer electrons during the redox reactions of metabolism
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.
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
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.
The production of ATP using energy derived from the redox reactions of an electron transport chain.
The formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism.
The entry compound for the Krebs cycle in cellular respiration; formed from a fragment of pyruvate attached to a coenzyme.
An iron-containing protein, a component of electron transport chains in mitochondria and chloroplasts
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. Provide a port through which hydrogen ions diffuse into the matrix of a mitrochondrion.
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.
Containing oxygen; referring to an organism, environment, or cellular process that requires oxygen.
Lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen and may be poisoned by it.
An organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions.
A metabolic sequence that breaks fatty acids down to two-carbon fragments which enter the Krebs cycle as acetyl CoA.
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.
An organism that obtains organic food molecules by eating other organisms or their by-products.
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.
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
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.
The second of two major stages in photosynthesis (following the light reactions), involving atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate.
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.
The entire spectrum of radiation ranging in wavelength from less than a nanometer to more than a kilometer.
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.
An instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution.
A type of blue-green photosynthetic pigment that participates directly in the light reactions.
A type of yellow-green accessory photosynthetic pigment that transfers energy to chlorophyll a.
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.
The chlorophyll a molecule and the primary electron acceptor in a photosystem; they trigger the light reactions of photosynthesis. The chlorophyll donates an electron, excited by light energy, to the primary electron acceptor, which passes an electron to an electron transport chain.
primary electron acceptor
A specialized molecule sharing the reaction center with the chlorophyll a molecule; it accepts an electron from the chlorophyll a molecule.
One of two light-harvesting units of a chloroplast's thylakoid membrane; it uses the P700 reaction-center chlorophyll.
One of two light-harvesting units of a chloroplast's thylakoid membrane; it uses the P680 reaction-center chlorophyll.
noncyclic 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+.
bundle sheath cell
A type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf.
A loosely arranged photosynthetic cell located between the bundle sheath and the leaf surface.
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.
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
Ribulose carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP, or ribulose bisphosphate).
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.
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.
A plant that prefaces the Calvin cycle with reactions that incorporate CO2 into four-carbon compounds, the end product of which supplies CO2 for the Calvin cycle.
sequence of events in the life of a cell, from its origin in the division of a parent cell until its own division into two composed of M, G1, S, and G2 phases
gene carrying structure found in nucleus- consists of 1 very long DNA molecules and associated proteins
replicated forms of chromosomes joined together by the centromere and separated during mitosis and meiosis II
a two stage type of cell division in sexually reproducing organims that results in cells with half the chromosomes number of the original cells
period when cell cycle when cell is not dividing- cell metabolic activity is high, chromsomes and organelles are duplicated and cell size may increase. 90% of cell cycle
first growth phase of the cell cycle, consisting of the portion of interphase, after DNA synthesis occurs
the second growth face of the cell cycle consisting of the portion of interphase after DNA synthesis occurs
the first subphase of mitosis in which the chromatin is condensing and the mitotic spindle begins to form but the nucleolus and nucleus are still in intact
a double membrane across the midline of a dividing plant cell between which the new cell wall forms during cytokenisis
The second subphase 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.
3rd subphase in mitosis; spindle is complete and the chromosomes attached to microtubules at their kinetochores are aligned at he metaphase plate
fourth subphase of mitosis in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell
the fifth and final subphase of mitosis in which daughter nuclei are forming and cytokenisis actually begins
an assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis
a specialized region on the centromere that links each sister chromatid to the mitotic spindle
prokaryotes cell division . Each daughter cell receives a copy of the single parental chromosome
cytokenisis process; pinching of the plasma membrane; the succession of rapid cell division without growth during early embryonic development that converts the zygote into a ball of cell
cell cycle control system
a cyclically operating set of molecultes in the cell that triggers and coordinates key events in the cell cycle
a non dividing face of the cell cycle consisting of the portion of interphase before DNA synthesis begins
a protein that must be present in the extracellular environment for the growth and normal development of certain types of cells
density dependent inhibitor
any factor that has a greater impact on a population as the population increases
a mass of abnormal cells within otherwise normal tissue, caused by the uncontrolled growth of a transformed cell
A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).
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.
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.
(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.
The generation-to-generation sequence of stages in the reproductive history of an organism.
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.
The reciprocal exchange of genetic material between nonsister chromatids during synapsis of meiosis I.
A haploid cell such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote.
A two-stage type of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original 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.
The multicellular diploid form in organisms undergoing alternation of generations that results from a union of gametes and that meiotically produces haploid spores that grow into the gametophyte generation.
The multicellular haploid form in organisms undergoing alternation of generations that mitotically produces haploid gametes that unite and grow into the sporophyte generation.
A paired set of homologous chromosomes, each composed of two sister chromatids. Tetrads form during prophase I of meiosis.
The X-shaped, microscopically visible region representing homologous chromatids that have exchanged genetic material through crossing over during meiosis.
The parent individuals from which offspring are derived in studies of inheritance; P stands for parental.
A phenotypic situation in which the two alleles affect the phenotype in separate, distinguishable ways
A type of inheritance in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.
law of segregration
Mendel's first law, stating that allele pairs separate during gamete formation, and then randomly re-form as pairs during the fusion of gametes at fertilization.
A diagram used in the study of inheritance to show the results of random fertilization.
An organism that is heterozygous with respect to a single gene of interest. A monohybrid results from a cross between parents homozygous for different alleles. For example, parents of genotypes AA and aa produce a monohybrid genotype of Aa.
law of independent assortment
Mendel's second law, stating that each allele pair segregates independently during gamete formation; applies when genes for two characteristics are located on different pairs of homologous chromosomes.
A type of inheritance in which F1 hybrids have an appearance that is intermediate between the phenotypes of the parental varieties
A phenomenon in which one gene alters the expression of another gene that is independently inherited
A heritable feature in a population that varies continuously as a result of environmental influences and the additive effect of two or more genes (polygenic inheritance).
A family tree describing the occurrence of heritable characters in parents and offspring across as many generations as possible.
A genetic disorder that occurs in people with two copies of a certain recessive allele; characterized by an excessive secretion of mucus and consequent vulnerability to infection; fatal if untreated.
sickle cell anemia
A human genetic disease of red blood cells caused by the substitution of a single amino acid in the hemoglobin protein; it is the most common inherited disease among African Americans.
A technique for determining genetic abnormalities in a fetus by the presence of certain chemicals or defective fetal cells in the amniotic fluid, obtained by aspiration from a needle inserted into the uterus.
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.
duchenne muscular dystropy
A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue.
The general term for the production of offspring with new combinations of traits inherited from the two parents.
A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes. The greater the frequency of recombination between two genetic markers, the farther apart they are assumed to be. See also genetic map.
A human genetic disease caused by a sex-linked recessive allele, characterized by excessive bleeding following injury.
An accident of meiosis or mitosis, in which the members of a pair of homologous chromosomes or sister chromatids fail to move apart properly.
A chromosomal condition in which a particular cell has an extra copy of one chromosome, instead of the normal two; the cell is said to be trisomic for that chromosome.
A chromosomal condition in which a particular cell has only one copy of a chromosome, instead of the normal two; the cell is said to be monosomic for that chromosome.
A chromosomal alteration in which the organism possesses more than two complete chromosome sets.
An aberration in chromosome structure resulting from an error in meiosis or mutagens; duplication of a portion of a chromosome resulting from fusion with a fragment from a homologous chromosome.
An aberration in chromosome structure resulting from an error in meiosis or from mutagens; specifically, reattachment of a chromosomal fragment to the chromosome from which the fragment originated, but in a reverse orientation.
A dense object lying along the inside of the nuclear envelope in female mammalian cells, representing an inactivated X chromosome.
(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.
The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.
An enzyme that links together the growing chain of ribonucleotides during transcription.
The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' 3' direction.
A discontinuously synthesized DNA strand that elongates in a direction away from the replication fork.
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 39 end of a new DNA fragment to the 59 end of a growing chain.
An already existing RNA chain bound to template DNA to which DNA nucleotides are added during DNA synthesis.
The cellular process that uses special enzymes to fix incorrectly paired nucleotides.
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.
A type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.
The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of "language" from nucleotides to amino acids
A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.
The DNA strand that provides the template for ordering the sequence of nucleotides in an RNA transcript.
A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.
A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA.
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
The removal of noncoding portions (introns) of the RNA molecule after initial synthesis.
A coding region of a eukaryotic gene. Exons, which are expressed, are separated from each other by introns.
A complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron, and joining the two adjacent exons.
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.
A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya.
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.
A specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.
The most abundant type of RNA, which together with proteins, forms the structure of ribosomes. Ribosomes coordinate the sequential coupling of tRNA molecules to mRNA codons.
base pair substitution
A point mutation; the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides.
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.
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.
(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.
The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complete in shape.