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211: Cell Biology > 5. Introduction to membrane transport > Flashcards

5. Introduction to membrane transport Flashcards

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1
Q

what is the membrane permeable to

A

gases
ethanol
urea and water

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2
Q

what is the membrane impermeable to

A

large uncharged molecules (glucose)
ions = K+, Mg+, Ca2+
charged polar molecules

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3
Q

define signal transduction

A

the rapid translocation of ions across a membrane which is involved in cell communication

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4
Q

the membrane allows compartmentalisation, what does this mean

A

means each organelle can have different ion concentrations and conditions

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5
Q

what are the three classes of transmembrane transporters

A
  1. pumps
  2. carriers
  3. channels
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6
Q

what are pumps used for

A

use ATP to pump ions against electrochemical gradients

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7
Q

what type of transport are pump transporters used for

A

primary active transport

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8
Q

what ions do pumps generally transport

A

H+ or Na+

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9
Q

summarise pumps:

A
  • use ATP to pump ions against gradient
  • primary active transport
  • transport mainly H+ and Na+
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10
Q

what type of transport do carriers engage in

A

secondary active transport

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11
Q

name 3 types of carrriers

A

symporters
antiporters
facilitators

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12
Q

what do symporters do?

A

use driver ion electrochemical gradient to drive other solutes in the same direction

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13
Q

what type of transporter establishes the electrochemical gradient for driver ions

A

pumps

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14
Q

what is the difference between symporters and anti porters

A

in symporters - the driver ions and solutes move in the same direction

in antiporters - the driver ions and solutes move in OPPPOSITE directions

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15
Q

what are facilitators, what can they not be?

A

allow facilitated diffusion down an electrochemical gradient
- cannot be energised

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16
Q

what is another term for facilitator

A

uniporter

17
Q

true or false: facilitators use driver ions? explain

A

false

- facilitators do not use driver ions but rather enables passive solute movement

18
Q

what is the third type of transmembrane transporters

A

ion channels

19
Q

describe ion channels

A

transport is passive down an electrochemical gradient

usually highy regulated - defined open and shut kinetics

selective for specific ions

20
Q

give an example of an antiporter, how do they work?

A

sodium calcium antiporters, they remove calcium from the cytosol or sodium symporters

21
Q

give an example of a channel, what is it involved in?

A

chloride channel

- role in osmoregulation

22
Q

plant and fungal cells have a proton economy what is this

A

means they use protons and proton primary pumps to generate a proton electrochemical gradient

23
Q

what is the Nernst equation used for

A

calculates the equilibrium potential

24
Q

define equilibrium potential

A

the membrane potential required to exactly counteract the chemical forces acting to move one particular ion across the membrane

25
Q

what pumps do animal cells have

A

sodium-potassium pump =

3 Na+ out, 2 K+ in

26
Q

what is the effect of the animal sodium-potassium pump

A

generates a large electrochemical gradient for sodium influx

27
Q

name a facilitator present in animals

A

glucose transporter

28
Q

plant and fungal cells have hydrogen pumps, what does this do

A

expels 1 hydrogen ion per ATP molecule hydrolysed

29
Q

what does the hydrogen pump generate

A

a large electrochemical gradient for H+ influx

30
Q

what is the most dominant channel in plants and fungi

A

K+ channels

31
Q

bacteria also have H+ pumps, what is the difference

A

rather than using energy from ATP

they act as a result of the electron transport chain

32
Q

how do bacterial carriers work

A

exhibit coupling to the H+ influx

33
Q

what is the most abundant transmembrane transporter

A

pumps

many more pumps than ion channels

34
Q

in the end-membrane, what pump expels H+

A

V-type H+ pumps

from the cytosol into the endomembrane lumen

35
Q

how many hydrogen molecules per ATP molecule in endomembrane H+ pump

A

2 H+ per ATP molecule

36
Q

what are most endomembrane carriers

A

antiporters

37
Q

what are endomembrane channels mainly involved in

A

membrane voltage regulation (calcium channels)

38
Q

how many ions do pumps transfer per second

A

~100

39
Q

how many ions do carriers transport per second

A

~1000

211: Cell Biology (20 decks)

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