the study of cell structure and function
sperm and oocytes (reproductive cells)
all cells in the body except reproductive cells (sperm and oocytes)
cell substance between the cell membrane and the nucleus, containing the cytosol, organelles, cytoskeleton, and various particles.
cells come from
division of preexisting cells
smallest units that perform physiological functions
each cell maintains its own state of ___
all body cells except sex cells (sperm and oocytes)
physical barrier separating cytoplasm from the extracellular environment
functions of plasma membrane
-barrier separating cytoplasm from extracellular fluid
-controls entry of nutrients and ions
-controls elimination of wastes
-receptors monitor environment and instigate needed changes in the cell
-structural support by attachment to other cells or material
plasma membrane is made of two layers of lipids
hydrophilic layer of plasma membrane
the outer surface of the membrane
hydrophobic layer of plasma membrane
the internal layer of the membrane
contains more K+, cytosol or extracellular fluid?
cytosol contains more potassium
contains more Na+, cytosol or extracellular fluid?
extracellular fluid contains more sodium
two classes of membrane proteins
1- integral proteins
2- peripheral proteins
integral membrane proteins
are a permanent part of membrane structure
peripheral membrane proteins
bound to the inner or outer surface of the membrane and can be removed without causing damage to the membrane
stabilize the cell by attaching it to other structures outside of cell and to the cytoskeleton inside the cell
recognition proteins (identifiers)
allow the immune system cells to recognize cells as "self" or "foreign"
catalyze chemical reactions inside or outside of the cells
sensitive to ligands which trigger changes in cellular activity
extracellular molecules that bind to receptors which then trigger changes is cellular activity
bind solutes and transport them across cell membranes
proteins with a central pore that forms a passageway across the membrane to permit movement of water and solutes
carbohydrates (glycoproteins, glycolipids, proteoglycans) that extend beyond surface of the plasma membrane forming a viscous layer for lubrication, protection, act as receptors and aid in recognition by immune cells.
the material between the plasma membrane and the nuclear membrane including cytosol, organelles, solutes, etc
which contains more suspended proteins cytosol or extracellular fluid?
cytosol contains more suspended proteins
cytosol contains reserve stores of ___ ___ and ___
carbohydrates, amino acids and lipids
masses of insoluble materials in cytosol (usually stored nutrients)
internal structures that perform specific tasks to maintain the health and life of the cell (the cells organs)
organelles not enclosed in a membrane. it's components are in direct contact with cytosol (cytoskeleton, centrioles, cilia, ribosomes, proteosomes)
organelles isolated from cytosol with phospholipid membranes (edoplasmic reticulum, Golgi apparatus, lysosomes, peroxismes, mitochondria and nucleus)
internal protein framework that provides cytoplasm with strength and structure. Made up of microfilaments, intermediate filaments and microtubules.
smallest element of cytoskeleton. composed of the protein actin.
functions of microfilaments
-anchor cytoskeleton to integral proteins on plasma membrane
-produce movement or change shape of cell
filaments of cytoskeleton that are larger than microfilaments but smaller than thick filaments. Made of various proteins. They are the most durable part of the cytoskeleton.
functions of intermediate filaments
-maintain cell shape (along with microfilaments)
-attach to plasma membrane to stabilize cell position
largest component of cytoskeleton. made up of protein called tubulin. they start at the centrosome and extend out into cytoplasm.
functions of microtubules
-provide cell strength and anchor organelles
-can be disassembled and reassembled to change shape of cell
-used as a system to move vesicles and other organelles inside of cell
-form spindle apparatus during cell division to move chromatids around inside of the nucleus
massive filament bundles composed of the protein myosin. They appear only in muscle cells and produce muscle contraction.
small finger-like projections on the surface of cells that absorb large amounts of material from extracellular fluid (such as cells lining the digestive tract). They increase the surface area of the cell so it is exposed to more of the extracellular environment.
cylindrical structures composed of microtubules that are found in all cells capable of cell division. They are made of 9 microtubules grouped in triplets (9+0 array). During cell division they form the spindle apparatus for moving chromatids around inside of nucleus. Microtubules begin here and project outward.
the region of cytoplasm that surrounds the centrioles
long, slender, hair-like extensions of the plasma membrane of some cells in respiratory and reproductive systems. They are made of 9 pairs of microtubules surrounding a central pair (9+2 array). The microtubules are anchored a basil body. They beat rhythmically to move fluid or secretions across the cell surface.
function of ribosomes
responsible for protein synthesis
the two subunits of ribosomes
small ribosomal unit and large ribosomal units. The two must join together with mRNA for protein synthesis to occur
two types of ribosomes
1- free ribososmes
2- fixed ribosomes
scattered throughout cytoplasm. synthesize proteins that enter the cytosol for use inside the cell
attached to rough ER (endoplasmic reticulum). They make proteins that are modified and packaged by ER for secretion outside of the cell
function of proteosomes
they remove proteins from cytoplasm that are damaged or abnormal (like those released from virus infected cells) and break them down to recycle the unable parts of the damaged protein
enzymes found in proteosomes that digest abnormal proteins making them proteolytic
network of flat sacs, hollow tubes and chambers (cisternae) connected to the nuclear membrane that:
-aid in protein synthesis
-absorb and neutralize drugs and toxins
two types of endoplasmic reticulum
smooth ER- has smooth surface
rough ER- has ribosomes along its outer surface
smooth ER function
-synthesizes lipids and carbohydrates for structure of other organelles
-synthesizes steroids and hormones
-synthesizes and stores glycogen in liver and muscle cells
-adjusts contents of cytosol by absorbing and storing excess substances (ie- Ca++, etc)
-detox of drugs/toxins in liver and kidney cells
rough ER function
proteins newly made by ribosomes on its surface are packaged and modified for export to next destination (most are packaged in transport vesicles for delivery to golgi apparatus
membranes formed around proteins modified by the rough ER that then transport the proteins to their next destination (usually the golgi apparatus)
looks like a stack of flattened sacs (cisternae). located near the nucleus. prepares proteins that it receives from the rough ER for exocytosis (enzymes, hormones, etc). It also packages special enzymes in vesicles for use in cytoplasm.
flattened sacs that contain fluid in the ER and golgi apparatus
digestive vesicles produced by the golgi apparatus that provide an isolated environment for dangerous chemical reactions within the cell (ie- the breakdown of large organic molecules).
contain inactive enzymes. once they fuse with the material to be digested their enzymes become activated and they become secondary lysosomes.
lysosomes that have fused with material to be digested and now contain active digestive enzymes
functions of lysosomes
-digest and recycle damaged organelles
-destroy bacteria, organic compounds or liquids that enter the cell
-after digestion of materials, the nutrients are released into cytosol and the unusable waste is eliminated through exocytosis
a cell is damaged and it's lysosomes disintegrate eleasing digestive enzymes into the cytoplasm. The enzymes rapidly destroy the cell's organelles, proteins and plasma membrane.
proteins made in the ___ ribosomes are released into cytoplasm for use in the cell.
free ribosomes make proteins for use in the cell
proteins made in the ___ ribosomes are folded and packaged to moved to the ER.
fixed ribosomes make proteins that then move into the ER and are eventually used outside of the cell
vesicles made in the golgi apparatus that fuse with the plasma membrane and release their contents outside of the cell (exocytosis)
membrane renewal vesicles
vesicles made in the golgi apparatus that add new proteins and lipids to the plasma membrane
steps of protein synthesis
1- mRNA leaves nucleus and attaches to ribosomes
2- ribosomes form the protein coded by the mRNA from amino acids
3- proteins made by free ribosomes move into cytoplasm, if made by fixed ribosomes proteins move into the ER
4- proteins are modified in hollow tubes of ER
5- a region of ER buds off forming a transport vesicle around the protein
6- transport vesicle moved protein to the golgi apparatus
7- enzymes modify protein in cisternae of GA and then they moved through and are released in vesicles on the other side of the golgi apparatus
vesicles that are smaller than lysosomes and contain digestive enzymes for breakdown of fatty acids. They protect the cell from hydrogen peroxide (H2O2) which is a free radical byproduct of fatty acid digestion.
the main enzyme responsible for breaking down hydrogen peroxide in peroxisomes. It is produced by free ribosomes and carried to peroxosomes by carrier proteins.
the repair, recycling and changes in composition that the plasma membrane goes through to adapt to environmental changes
"powerhouse of the cell" responsible for energy (ATP) production via the breakdown of carbohydrates
cristae of mitochondria
the many folds of the inner membrane of the mitochondria that contains the fluid contents (matrix)
the fluid inside the cristae of the mitochondria
most chemical reactions that release energy occur in the ___
most chemical reactions that use energy occur in the ___
steps of mitochondrial energy production (aerobic respiration b/c O2 is the final electron acceptor)
1- glycolysis occurs in the cytoplasm (1 glucose is broken down into 2 pyruvate molecules)
2- mitochondria absorbs pyruvate
3- in matrix CO2 is removed from pyruvate
4- Citric acid cycle (Krebs cycle) occurs
5- CO2 is released as waste
6- hydrogen produced by krebs cycle is oxidized electron transport chain
7- ATP is produced
mitochondria absorb ___ and ___ and generate ___ and ___.
absorb pyruvate and O2 and generate CO2 and ATP
largest organelle. control center of cell. determines structure and function of the cell.
double membrane that separates nucleus from cytosol
the space between the two layers of the nuclear envelope
what organelle is externally connected to the nuclear envelope?
the rough ER
large proteins in nuclear envelope that allow chemical communication between nucleus and cytoplasm
the fluid in the nucleus
network of filaments in nucleoplasm that provide structure and support
transient organelles inside nucleus that synthesize rRNA and produce the ribosomal subunits
complex formed by double helix DNA strands wound around a core of histones
when cells are not dividing, nucleosomes are loosely coiled (a tangled mess)
the form that nucleosomes take on when they coil tightly just before cell division
humans have how many pairs of chromosomes?
the chemical language the cell uses to code for functional products
the nitrogenous bases of complementary DNA strands are held together by ___ bonds
the identity of a single amino acid is stored in sequences of three nitrogenous bases
the functional unit of heredity. contains all the DNA triplets needed to produce specific proteins
before protein synthesis the hydrogen bonds between nucleotides are broken, the histones are removed and RNA polymerase binds to the promoter site on the DNA
"to copy" -its the synthesis of RNA using DNA as a so that the info can be taken to the ribosomes by mRNA for protein synthesis
mRNA (messenger RNA)
is made in the nucleus during transcription using DNA as a template. mRNA then takes the info for protein synthesis into the cytoplasm to bind ribosomes
enzyme that creates RNA from DNA
one of the two strands of DNA. during transcription this is the strand that contains the genes for specific proteins
one of the two strands of DNA. during transcription, this strand is complementary to the coding (functional) strand so when a strand of RNA complementary to the template strand is made, it is identical to the coding strand of DNA
three nucleotide bases on RNA that are complementary to a triplet of bases on the template DNA strand (which makes them identical to a triplet on the coding (functional strand)
after transcription, all of the nonsense regions of RNA that are not needed to build a protein are removed and all of the necessary regions are spliced together
the assembling of a functional polypeptide
formation of a linear chain of amino acids using the info provided by a strand of mRNA (translated from mRNA language to amino acid language)
tRNA (transfer RNA)
acts as a transfer truck, it delivers the appropriate amino acids to the ribosome that are needed to build the peptide coded by the mRNA attached to the ribosome
sequence of three bases on mRNA
sequence of three bases on tRNA that are complementary to codons on mRNA.
protein synthesis summary
1-gene activation- DNA is uncoiled and histones removed
2-transcription- mRNA is made from DNA in nucleus
3-mRNA moves to cytoplasm
4-mRNA binds ribosomes
5-translation- tRNA binds ribosomes and tRNA delivers amino acids coded by mRNA to form the specific protein
passive movement of a solute from an area of high concentration to an area of low concentration (down the concentration gradient)
the difference between high and low concentrations of a substance
factors that affect diffusion
the two ways an ion or molecule can diffuse across the plasma membrane
1-crossing the lipid portion of the membrane
2-passing through a membrane channel
passageways through proteins in the plasma membrane
passive channels that are permanently open to allow passage across membrane
movement (diffusion) of water across membrane. "water follows salt" -water moves towards area with higher solute concentration
the force with which water moves into a solution because of its solute concentration
pressure against fluid
most membranes are freely permeable to ___
total solute concentration of a solution
how the fluid affects the cell (fluid shift)
causes no fluid shift
less solute than the cell. causes water to flow into the cell
more solute than the cell, causes water to flow out of the cell
water flows into a red blood cell in a hypotonic solution causing it to swell and rupture
fluid leaves the cell when placed in a hypertonic solution which causes the cells to dehydrate and shrivel up
carrier mediated transport
proteins bind specific molecules and carry them across the plasma membrane
when a carrier protein can bind more than one type of molecule and transport two substances the same direction at the same time
carrier protein transports one substance into cell and then binds a different substance and transports it out of the cell
two types of carrier mediated transport
carrier proteins transport substances across membrane down the concentration gradient (uses no ATP)
carrier proteins move molecules against the concentration gradient. requires ATP
carrier proteins that move sodium, potassium, calcium and magnesium across membranes
ion pumps that perform countertransport
the carrier protein sodium-potassium carrier protein that is active is sodium-potassium exchange pumps
secondary active transport
doesn't use ATP for transport but must use it to maintain homeostasis after the transport (ex- glucose can be transported into the cell with sodium but later ATP is required to move sodium back out of the cell)
materials are moved in or out of the cell in vesicles that form at, or fuse with, the plasma membrane
two types of vesicle transport
extracellular materials (fluids and solutes) are packaged in vesicles at the cell membrane and brought into the cell. Lysosomes then bind to the vesicle and digest it or digest the material inside for use by the cell.
three types of endocytosis
receptor mediated endocytosis
when a specific target ligand binds the receptors on plasma membrane the ligand is then enclosed in a vesicle and brought into the cell
"cell drinking" -extracellular fluid is brought into the cell in vesicles
uses pseudopods to engulf a large solid object (bacteria, etc) and form a vesicle around the object bringing it into the cell for digestion/destruction
vesicle inside of the cell moves towards the plasma membrane and fuses with it, vesicle contents are released outside the cell. used to expel hormones, waste products, etc.
types of passive transport (dont require ATP)
simple diffusion, osmosis, facilitated diffusion
types of transport that require ATP
active transport, secondary active transport, endocytosis and exocytosis
is the inside of the cell positively or negatively charged?
negative charge due to proteins in cytoplasm
is the extracellular fluid positively or negatively charged?
positive charge due to cations in extracellular fluid
the difference between an positive and negative charge when they are separated by a barrier
the difference between the + charge outside the cell and the - charge inside the cell. they are separated by the plasma membrane
the unit of measure of potential difference
transmembrane potential of an undisturbed cell
one thousandth of a volt
stored energy that can be released to do work (like the energy of the transmembrane potential)
some processes that rely on transmembrane potential?
transmission of nerve impulses, muscle contraction, secretion by glands
a cell divides into two identical daughter cells
programmed cell death. some cells have a gene that causes the cell to destroy itself under certain conditions
duplication of a cell's DNA
division of the cell's nucleus in somatic cells
the formation of sex cells
make up of a DNA molecule
two strands of DNA with complementary nitrogenous bases that are held together by hydrogen bonds
the enzyme that unwinds DNA and disrupts the hydrogen bonds between its nitrogenous bases prior to DNA replication
enzyme that binds nitrogenous bases with complementary nucleotides dissolved in nucleoplasm.
chemical bond characterized by one or more pairs of shared electrons.
any of a class of enzymes that catalyse the formation of covalent bonds and are important in the synthesis and repair of biological molecules, such as DNA
the phase of a cell's life cycle when the cell is performing normal functions of the cell and if necessary preparing for cell division
the four phases of interphase
G0=cell performing normal functions
G1=cell begins preparation for division by producing enough organelles for 2 complete cells
G2=last minute protein synthesis before cell division
division of cytoplasm into two new cells (the final stage of cell division)
The stages of mitosis
"toilet rug" P-MAT:
Stages of cell life cycle
1- interphase (normal function and prep for division)
2- mitosis [nuclear division] (prophase, metaphase, anaphase, telophase)
3- cytokinesis (cytoplasm divides)
copy of original DNA created during DNA replication
DNA replication occurs at what stage of life cycle?
the S phase of interphase when the cell is preparing for mitosis
the point where two chromatids (new strands of DNA) are connected to each other
rate of cell division
cells that maintain the cell population by repeated cycles of cell division. Their only function is reproduction. each division produces one normal functioning cell and one stem cell.
M-phase promoting factor
enzyme made of the proteins Cdc2 and cyclin that triggers cell division in some cells when levels get high enough
hormones (peptides) that stimulate cell division
genes that inhibit cell division
the terminal protective covering on the ends of DNA strands (tips of the shoelaces). with each division part of telomere breaks off. When it gets to short it signals repressor gene to stop division
an abnormality causes cell growth and division to exceed the rate of cell death causing tissue to enlarge
when tumor cells spread to surrounding tussue
when malignant cells spread to far away tissue via the circulatory or lymph systems and create a secondary tumor
a tumor far away from the original tumor
A tumor that does not metastasize or invade and destroy adjacent normal tissue.
A tumor that invades surrounding tissues, is usually capable of producing metastases, may recur after attempted removal, and is likely to cause death unless adequately treated.
the mutated genes that control cell growth causing malignancy (cancer)
illness where genetic mutations in cells disrupt control of cell growth and division causing malignant cells
the development of specific cell features by "turning off" certain genes (all body cells have the same DNA. their structure and function is determined by which genes are used and which are not) [ie-liver cells and muscle cells have same DNA they just use different sets of the genes on that DNA]
specialized cells with specific capabilities grouped together for a common function