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Animal Cell Bio > plamsa membranes > Flashcards

plamsa membranes Flashcards

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Biology 101 flashcards
1
Q

channel protein

A

pores that accommodate size/change of a specific solute

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2
Q

gated ion channel

A

open and close to control ion passage

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3
Q

carrier protein

A

binding sites for solutes, require conformational change

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4
Q

passive transport

A

do not require energy
simple diffusion, osmosis, facilitated diffusion

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5
Q

active transport

A

requires energy
primary requires atp
secondary does not

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6
Q

receptors

A

bind chemical signals

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7
Q

second messenger systems

A

communicate within cell

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8
Q

enzymes

A

catalyze reactions including digestion of molecules

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9
Q

carriers

A

bind solutes and transfer them across the membrane

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10
Q

cell identity markers

A

glycoproteins act as unique tag

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11
Q

cell adhesion molecules

A

mechanically link cell to another cell or to extracellular matrix

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12
Q

what is special about channel proteins

A

they have specificity and use facilitated diffusion (passive)

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13
Q

what is osmosis

A

a specialized form of facilitated diffusion through a channel protein (aquaporin protein channels)

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14
Q

what is special about gated ion channels

A

require a stimulus to transport solutes via facilitated diffusion and have specificity, 3 types (chemically and voltage and mechanically )

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15
Q

chemically gated ion channel

A

chemical messenger (ligand) binds to protein and induces opening
ex : acetylcholine neurotransmitter binds to its receptor on target cell and permits passage of Na and K ions

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16
Q

voltage gated ion channels

A

change in voltage along the length of a neuronal axon induces opening
ex : Na channels opening along axon to allow influx of Na ions

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17
Q

mechanically gated ion channels

A

force on cell membrane physically opens channel
ex: move of fluid in inner ear membrane and opening ip k channels

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18
Q

what is special about carrier proteins

A

carried out by facilitated diffusion or active transport
glucose transporter protein permits transport of glucose
requires conformational change
carrier has a solute binding site and 2 conformational states
bi directional transport and always down glucose concentration gradient

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19
Q

what is active transport

A

requires energy
vesicular transport mechanisms (endo/exocytosis)
carrier transport proteins - coupled transport and atp driven pumps

20
Q

primary active transport (Ca++ ATPase)

A

driven by atp hydrolysis
in domain the atp and ca are open to cystolic side and ca2+ protein activates atpase
atp is hydrolyzed and P domain is phosphorylated
conformational change and Ca++ is released to SR lumen
ADP and Pi released

21
Q

Primary active transport of Na+ and K+ ATPase

A

cytoplasmic NA binds to sodium potassium pump

Na binding stimulus phosphorylation by ATP

Phosphorylation causes the protein to change its conformation expelling Na to the outside

extracellular k binds to the protein, triggering release of the phosphate group

loss of phosphate restores the proteins original conformation AND K is released and Na sites are receptive again

Hydrolysis one ATP pump 3 Na out and 2 K into cell

22
Q

secondary active transport - coupled transporters

A

electrochemical gradient of one solute us used as energy source to pump another solute “hijacking”

Na moves down its gradient
glucose moves against its gradient
both move ecf to ice
SLGLT1 protein uses the Na gradient which was established by the Na-k pump as an energy source to transport glucose

atp hydrolysis used indirectly = secondary active transport

23
Q

membrane potential

A

all living cells have one

used as a source of potential energy to”do work”
for subset of cells (electrically excitable) membrane

potential be changed for purposes of cell signaling or changing function
membrane potential is between -60 - -90 mV

portion of membrane facing icf is negative

24
Q

how is the membrane potential established?

A

ion concentration gradient and selective ionic permeability

25
Q

Na-K cell gradient established

A

Na is being pumped out against it’s gradient to get intracellular pool of na established it also must be entering the cell

if k is being pumped into the cell against its gradient then the extracellular pool of k is established by k also leaving the cell

26
Q

leak channels

A

Na doesn’t have leak channels bu k does

leak channels allow k to move down concentration gradient and exit the cell which contributes to a positive charge on ecf side

Na enters cell via coupled transport

process

membrane has selective ionic permeability for K+
Ecf gains + while icf gains - charge
uneven distribution of charge along lipid bilayer
electrostatic interactions
resting membrane potential

27
Q

sum of Na and K permeability with concentration gradient

A

ion concentration gradient (Na/K pump) and selective ionic permeability (K leak channels) establish resting membrane potential

also need to consider electrochemical gradient and not concentration gradient

28
Q

when k leaves through leak channels (electrochemical)

A

at equilibrium k is zero
but when it leaves chemically downhill high to low
electrically uphill negative to positive
at equilibrium electrochemical gradient is 0

29
Q

ions move down their concentration gradient until equilibrium is achieved but what are some conditions

A

steeper gradient = greater tendency of ions to move down gradient
stronger electrical field = greater tendency of ions to move down the gradient
weaker electrical field = lesser tendency of ions to move down gradient

30
Q

adding potassium to the cell

A

makes concentration different and more positive and more electrically excitable

31
Q

action potential

A

changing the membrane permeability to select ions to allow those ions in and out cel
is triggered when threshold potential is reached (-40 mV)
propagates along the length of the cell membrane
membrane permeability is regulated by gated ions

32
Q

synapse

A

site of communication
delivery of neurotransmitters
from pre synaptic to post synaptic cell

33
Q

permeability of K and Na inside and outside the membrane

A

K permeability inside membrane way higher than Na while the opposite on the outside, Na is more permeable

34
Q

What happens when Na gates open in membrane (action potential)

A

Na flows into the cell and membrane potential becomes more positive = depolarization

35
Q

What happens when Na channels close (action potential)

A

K channels are open but they are slow and membrane potential becomes more negative = repolarization

36
Q

What happens when K channels are slow (action potential)

A

K continues to leave the cell and membrane potential becomes more negative than RMP = hyperpolarization

37
Q

steps of action potential

A

resting potential
depolarization
peak action potential
repolarization
hyper polarization

38
Q

as membrane becomes more permeable to Na

A

membrane potential approaches ENa+

39
Q

Features of voltage gated Na channels

A

pore forming domains with selectivity filter (specificity for Na ions)

voltage sensors enriched in positively charges amino acids

inactivation gate “hinge”

K channels also have voltage sensors and pore forming domains but no inactivation gate

40
Q

The Na channel has three distinct configurations

A
  • Voltage gated Na channel closed at RMP, negative charge on inside of membrane = inward pull of voltage sensors

-Voltage gated Na channel; open at depolarization, slight influx of Na = voltage sensors relax upward = increased Na permeability = greater influx of Na

-voltage gated Na channels inactivated quickly - rapid decrease in Na permeability

41
Q

K channels has open and closed configurations

A

-Voltage gated K channel closed at RMP, negative charge on inside of membrane = inward pull of voltage sensors

-voltage gated k channel open at depolarization but opening is slow. Slight influx of Na = voltage sensors relax slowly = increase k permeability lags behind increased Na permeability

They are finally open at the time the Na channels are in activated, they are slow to close

42
Q

At each stage when are the channels open or closed

A

Resting membrane potential - K and Na both closed
Depolarization - K slow to open, Na open and influx
Action potential - Na inactivated, K slow to open
Depolarization - K open and efflux, Na switching from inactivated to closed
hyper polarization - K slow to close and inward pull of voltage sensors to close K channels and more negative charge
resting memorable potential - K closed and Na switches from inactivated to closed.

43
Q

action potential is unidirectional

A

when Na channels are inactivated they cannot be opened even with another stimulus

44
Q

what does the action potential do

A

brings the signal down the axon down the axon of the presynaptic neuron

45
Q

synaptic transmission continues as long as

A

Action Potential propagates to the synapse
membrane receptors are expressed
neurotransmitters are available in synaptic cleft

46
Q

what is synaptic transmission

A

action potential propagates down the axon Na influx and K efflux

AP induces opening of voltage gated Ca++ channels in synaptic knob

Ca++ enters knob (down its concentration gradient) and induces synaptoagmin (protein associated with synaptic vesicle) to interact with the snare protein complex (at plasma membrane) vesicle membrane fuses with plasma membrane

Neurotransmitters are released into the synaptic cleft

Neurotransmmiter diffuses across cleft and bind to neurotransmitter receptor

Receptor serves as a chemically ligand gated ion channel that opens and permits ion transport across plasma membrane

induces localized change in membrane potential (depolarization or hyper polarization, depending on which ion crosses membrane)

Localized depolarization triggers opening of voltage gated Na and K channels on adjacent segment of membrane

Animal Cell Bio (5 decks)

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