Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
93 Cards in this Set
- Front
- Back
fluid mosaic model |
phospholipid bilayer as lipid "lake" in which variety of proteins "swim" |
|
where are hydrophilic portions? |
exposed to water on one/both sides in cytosol or on extracellular surface |
|
where are hydrophobic portions? |
within plasma membrane |
|
bilayer organization |
hydrophobic nonpolar fatty acid tails associate and hydrophilic polar heads face out |
|
what influences fluidity of membrane |
chain length of fatty acid tails presence of polar groups degree of saturation temperature |
|
longer chains of fatty acids are ________ fluid than shorter chains |
less |
|
unsaturated carbon chains are _______ fluid than saturated chains |
more |
|
higher temperature, ______ fluid |
more |
|
steroids |
family of carbon compounds with multiple linked rings ex. cholesterol- helps maintain membrane fluidity |
|
peripheral membrane proteins |
loosely associated with hydrophilic end not embedded in bilayer lack hydrophobic groups, do not cross into core of bilayer |
|
integral membrane proteins |
cross into hydrophobic portion of bilayer cannot be removed without disrupting whole membrane both hydrophilic and hydrophobic portions |
|
transmembrane protein |
integral protein that completely crosses entire membrane protrudes on both sides |
|
anchored membrane proteins |
membrane proteins with fatty acids or other lipid groups covalently attached to them |
|
can all proteins move within bilayer? |
no, some can but others cannot because they are impeded by other proteins OR attached to cytoskeleton |
|
glycoprotein |
one or more short carb chains covalently bonded to protein |
|
glycolipid |
carb covalently bonded to lipid |
|
proteoglycan |
protein with even more, longer carb chains attached |
|
why do membranes constantly change?
|
dynamic ability of lipids to spontaneously associate with each other |
|
selective permeability |
some can enter others can't |
|
examples of permeable substances
|
oxygen and CO2 can cross through simple diffusion |
|
examples of non-permeable substances |
large molecules, polar molecules, charged molecules, glucose, potassium, sodium, H ions, chloride, magnesium, calcium cannot diffuse without transporter |
|
passive transport |
diffusion across membrane no need for energy input |
|
types of passive transport |
simple diffusion facilitated diffusion |
|
diffusion |
tendency of molecules to spread out in available space in random movement towards equilibrium net movement high to low concentration |
|
simple diffusion |
passive diffusion across phospholipid bilayer
no protein transport no energy input |
|
what affects diffusion speed? |
diameter of molecules: smaller=faster temp: higher=faster concentration gradient: greater difference=faster |
|
natural tendency to go high to low concentrations does what in terms of free energy and entropy? |
releases free energy entropy increases |
|
osmosis |
diffusion of WATER through semipermeable membrane higher solute conc. = lower H2O conc. |
|
osmotic pressure |
pressure that needs to be applied to solution to PREVENT flow of H2O across membrane by osmosis pi= cRT |
|
hypotonic |
solution that is hypotonic to another solution has LOWER conc. solutes than other cell will expand, can burst! |
|
turgor pressure |
pressure that builds up against cell wall as water flows inside cell keeps green plant parts upright if enough water leaves cell, turgor pressure drops, plant wilts |
|
when is plant cell healthiest? when is animal cell healthiest? |
plant: when turgid (firm state when cell in HYPOtonic environment and water is pushing out onto cell wall) animal: isotonic environment |
|
hypertonic |
solution that is hypertonic to another solution has HIGHER conc. solutes than other cell shrivels |
|
isotonic |
solution is isotonic to another solution if both have SAME conc. solutes stable size |
|
facilitated diffusion |
passive movement of molecules down conc. gradient using TRANSPORT PROTEIN |
|
types of transport proteins |
channel proteins carrier proteins |
|
channel proteins |
type of transport protein under facilitated diffusion
integral membrane proteins that form hydrophilic channels across membranes do NOT change shape two kinds: gated channels and aquaporins |
|
types of channel proteins |
gated ion channels aquaporins |
|
gated ion channels |
channel protein that opens and closes in response to a stimulus, selectively allowing ions to move down conc. gradient 2 kinds: ligand-gated and voltage-gated |
|
ligand-gated channel |
type of gated ion channel, which is a type of channel protein, which is a transport protein all under facilitated diffusion |
|
voltage-gated channel |
type of gated ion channel, which is a type of channel protein, which is a transport protein all under facilitated diffusion
responds to change in voltage (electrical charge) along membrane |
|
aquaporins |
type of channel protein, which is transport protein under facilitated diffusion channels that allow large amounts of water to move down conc gradient |
|
which protein changes shape to transport molecules into the cell? |
carrier proteins |
|
carrier proteins |
transport protein that takes in polar molecules like sugars and aminos CHANGES SHAPE, allows molecules inside |
|
what affects rate of facilitated diffusion? when does it reach max? |
saturation of carrier molecules rate of diffusion reaches maximum when ALL carrier molecules fully saturated (loaded w solute molecules) |
|
do channel proteins require energy input? |
no |
|
do carrier proteins require energy input? |
no |
|
active transport |
movement of substance against normal flow, against conc. gradient energy input! two types: primary and secondary |
|
difference between passive and active transport |
active transport requires energy (ATP) and REDUCES entropy passive transport does not require energy and INCREASES entropy |
|
types of active transport |
primary secondary |
|
primary active transport |
involves direct hydrolysis of ATP to generate energy necessary to move substance vs conc. gradient |
|
sodium-potassium pump |
membrane protein that uses 1 ATP to pump 3 sodiums OUT and 2 potassiums IN, against their conc. gradients |
|
secondary active transport |
indirectly uses ATP to set up gradient involves coupling of downhill diffusion of one substance and uphill transport of another against conc. gradient move against gradient by "hitching a ride" with other ions moving down gradient OR by transport protein |
|
protein transporters only effective for _______ molecules |
small |
|
how do larger molecules cross membrane? |
exocytosis and endocytosis |
|
endocytosis |
movement of large molecules into cell involves vesicles 3 kinds: phagocytosis, pinocytosis, receptor-mediated endocytosis |
|
phagocytosis |
"cell-eating" binding of ligand and receptor causes cell to engulf particle, forming a phagosome phagosome fuses with lysosome and is digested |
|
pinocytosis |
"cell-drinking" vesicles bring fluids and dissolved substances in nonspecific |
|
receptor-mediated endocytosis |
ligands bind to receptors on cell membrane and trigger vesicle formation highly specific receptors located in coated pits with clathrin inside cell, loses clathrin |
|
clathrin |
in receptor-mediated endocytosis covers cell surface exposed to cytoplasm stabilizes vesicle |
|
exocytosis |
movement of large molecules out of cell via vesicles that fuse with cell membrane |
|
where do the coated vesicles go? |
fuse with lysosome OR eventually with cell membrane |
|
example of receptor-mediated endocytosis in mammalian cells |
cholesterol located in LDLs, circulated in blood LDL binds to receptors that recognize protein clathrin molecules coat interior membrane, bend, and form vesicle inside, coat comes off, fuses with endosome (receptors go back to membrane) endosome fuses with lysosome, cholesterol released in cytosol |
|
signal transduction pathway |
series through which signal binds to receptor and causes response signal, receptor, response |
|
autocrine signaling |
affects the same cell that releases it self-stimulation |
|
paracrine signaling |
diffuse to and affects adjacent cells |
|
endocrine signaling |
hormone secreted through bloodstream to reach distant cells |
|
juxtracrine signal |
requires direct contact between signaling and responding cell interaction btw signaling molecules bound to cell surfaces |
|
ligand |
chemical signal that binds to receptor noncovalently (weak) and reversibly highly specific does not contribute further, simply "knocks on the door" |
|
allosteric regulation |
alteration of 3D shape of protein as result of binding to non-active site triggers signal transduction, can cause short or long term response |
|
cytoplasmic receptors |
located in cytoplasm or nucleus |
|
membrane receptors |
located on membrane |
|
what kinds of molecules would have membrane receptors? |
large or polar signal molecules... CANNOT cross membrane! |
|
what kinds of molecules would have cytoplasmic receptors? |
small hydrophobic signal molecules... CAN cross membrane steroids and thyroid hormones (estrogen, testosterone, cortisol) |
|
transcription factors |
turn on specific genes |
|
antagonist/inhibitor |
binds to receptor and prevents ligand binding |
|
ion channel receptors |
on plasma membrane changes shape when ligand binds to it, either allows or restricts flow of ions into cell ligand-gated ion channel receptors such as acetylcholine receptor control sodium flow |
|
do ion channel receptors require energy? |
no! they are not pumps, they control flow down conc. gradient |
|
protein kinase receptors |
on membrane, also changes shape can initiate multiple signal transduction pathways at one time ligand binding activates phosphorylation (addition of phosphate groups) |
|
kinase |
molecule that phosphorylates other molecules |
|
example of protein kinase receptor |
tyrosine kinase receptor two membrane proteins come together, tyrosines are phosphorylated ATP + protein ---> ADP + phosphorylated protein phosphorylated tyrosine heads activate different types of relay proteins that attach to them, resulting in different responses |
|
G protein linked receptors |
on membrane what sticks out into extracellular surface is receptor, what extends into cytoplasm interacts with G protein |
|
G protein |
bound to cytoplasmic side of membrane bound to GDP= inactive bound to GTP= active can bind to receptor, GDP and GTP, and effector protein (amplifies signal) |
|
what happens when G protein linked receptor activated? |
GTP replaces GDP, effector protein activated=amplification eventually, G protein acts as GTPases and turn themselves off- self regulation |
|
second messengers |
small nonprotein water soluble molecules or ions that acts as intermediate btw activated receptor and cascade of events ex. cAMP |
|
cAMP |
cyclic AMP created by adenylyl cyclase (enzyme in plasma membrane) activates protein kinase by noncovalent bonding, changes shape! (kinase goes on to phosphorylate others and amplify signal) |
|
cellular responses |
opening ion channels alterations in gene expression (on/off) alteration of enzyme activity |
|
which is fastest cell response |
alteration of enzyme activity |
|
true or false. same signal can lead to different response. |
TRUE epinephrine ACTIVATES signal transduction in heart m. cells but INHIBITS target enzyme in digestive tract |
|
what determines cellular response? |
balance btw signal enzymes and regulating enzymes cells alter balance by synthesis/breakdown of enzymes OR activation/inhibition of enzymes by other molecules |
|
adenylyl cyclase |
enzyme in plasma membrane makes cAMP from ATP with liberation of pyrophosphate |
|
if conc. of epinephrine drops, cAMP conc. in liver cells expected to _________ because ____________ activity would _________ |
decrease adenylyl cyclase decrease |
|
epinephrine binding to receptor leads to ___________ |
more cAMP production |