Chapter 7: Membrane Structure and Function Flashcards

1
Q

selective permeability

A

some substances cross plasma membrane more easily

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2
Q

amphipathic

A

hydrophilic region and hydrophobic region

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3
Q

fluid mosaic model

A

membrane is a fluid structure with a mosaic of proteins (hydrophobic regions inside phospholipid bilayer with hydrophilic regions protruding out)

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4
Q

freeze fracture

A

cell is frozen and fractured with a knife. splits the center of phospholipid bilayer into two separated layers. Each membrane protein goes wholly into one of the layers.

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5
Q

membrane movement

A

membrane held together by hydrophobic interactions so most lipids (10^7 times per second) and some proteins shift laterally (not transversely).

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6
Q

membrane fluidity

A

membrane solidifies as temperature decreases. fluidity depends on type of lipids (saturated solidifies more easily than unsaturated, which has kinks in tails)

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7
Q

cholesterol

A

steroid that acts as membrane fluidity buffer. at high temps, restrains phospholipid movement. at low temps, prevent phospholipids from packing too close together.

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8
Q

effects of membrane fluidity

A

solidified membrane has different permeability and enzymes may become inactive. too fluid membranes cannot support protein function.

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9
Q

integral proteins

A

penetrate hydrophobic interior of lipid bilayer. majority are transmembrane. hydrophobic regions consist of 1+ stretches of nonpolar amino acids coiled into α helices.

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10
Q

transmembrane protein

A

span the membrane

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11
Q

peripheral proteins

A

loosely bound to surface of membrane (not embedded in lipid bilayer), often to exposed parts of integral proteins.

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12
Q

membrane protein attachments

A

cytoplasmic side: attach to cytoskeleton
extracellular side: attach to ECM

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13
Q

functions of membrane proteins

A

transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to cytoskeleton and ECM (coordinate extra and intra cellular changes)

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14
Q

glycolipids

A

lipids with covalently bound carbohydrates

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15
Q

glycoproteins

A

proteins with covalently bound carbohydrates

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16
Q

HIV infection

A

HIV binds to CD4 receptor on cell and also needs to bind to CCR5 coreceptor in order to infect cell

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17
Q

permeability of lipid bilayer

A

hydrophobic (nonpolar) molecules like O2, CO2, hydrocarbons, diffuse easily. hydrophilic (ions + polar) molecules diffuse slowly.

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18
Q

transport proteins

A

help hydrophilic substances cross lipid membrane

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19
Q

channel proteins

A

have hydrophilic channel that molecules/ions use as tunnel.

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20
Q

aquaporins

A

channel proteins for water. (3 * 10^9 water molecules per second)

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21
Q

carrier protein

A

bind to and change shape to shuttle molecule/ion across membrane

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22
Q

diffusion

A

movement of molecule so it spreads out evenly

23
Q

concentration gradient

A

region along which density of substance increases/decreases

24
Q

passive transport

A

energy is not expended

25
osmosis
diffusion of free water across selectively permeable membrane
26
tonicity
ability of surrounding solution to gain/lose water. depends on partly on its concentration of nonpenetrating solutes
27
isotonic
same tonicity. no net movement of water across plasma membrane
28
hypertonic
more nonpenetrating solutes. cell loses water
29
hypotonic
less nonpenetrating solutes. cell gains water
30
osmoregulation
control of solute concentration and water balance
31
turgor pressure
back pressure from rigid cell wall (plant cell) that opposes further water uptake
32
turgid
very firm. needs hypotonic solution
33
flaccid
limp. caused by hypertonic/isotonic solution
34
plasmolysis
as plant cell loses water, plasma membrane shrinks away from cell wall. causes plant to wilt.
35
facilitated diffusion
proteins assist with passive diffusion of impermeable substances
36
ion channels
channel proteins that transport ions
37
gated channels
channels that open or close in response to stimulus.
38
active transport
expends energy. enables cells to maintain internal concentrations of solutes.
39
cystinuria
absence of carrier protein that transports cysteine and other amino acids across membranes of kidney cells. causes painful kidney stones
40
sodium potassium pump
exchanges Na+ for K+ across the plasma membrane. Steps: 1. 3 Na+ bind, triggers phosphorylation by ATP (reduces affinity for Na+, increases affinity for K+) 2. Na+ released outside the cell. 2 K+ bind, causing phosphate group to be released 3. 2 K+ released inside the cell, and because the protein shape is restored the cycle repeats.
41
voltage
electrical potential energy; separation of opposite charges
42
membrane potential
voltage across a membrane. negative, because inside of the cell is more negative than the outside
43
electrochemical gradient
combination of chemical force (concentration gradient) and electrical force (membrane potential) acting on an ion
44
electrogenic pump
transport protein that generates voltage across a membrane animals: sodium-potassium pump plants, fungi, bacteria: proton pump
45
proton pump
actively transports protons (H+) outside the cell
46
cotransport
active transport driven by a concentration gradient.
47
sucrose-H+ cotransporter
couples downhill diffusion of H+ into a plant cell to active transport of sucrose into the cell
48
exocytosis
transport vesicles fuse with plasma membrane to secrete molecules outside the cell
49
endocytosis
cell takes in substances by forming new vesicles from plasma membrane
50
Low-density lipoproteins
complex of lipids and proteins that transport cholesterol. binds to LDL receptors on plasma membranes and enter cell through endocytosis
51
familial hypercholesterolemia
high level of cholesterol in the blood because of defective LDL receptors
52
phagocytosis
cell engulfs particle by wrapping pseudopodia around it and forming a food vacuole (which fuses with a lysosome)
53
pinocytosis
cell "gulps" droplets of extracellular fluid (with molecules) into vesicles. nonspecific transport
54
receptor-mediated endocytosis
allows for bulk transport of specific substances 1. proteins with receptor sites exposed to extracellular fluid are embedded in the plasma membrane. 2. Ligands (for receptors) bind 3. Receptor proteins cluster in coated pits (lined with fuzzy proteins on cytoplasmic side) 4. after receptors are emptied, the vesicle returns them to plasma membrane