1 2 Membrane Transport: Passive and Active Flashcards

1
Q

___, like ___ and ___ are highly lipid soluble and easily pass though the PM

A

gasses like oxygen and carbon dioxide

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2
Q

lipid bilayer is made of

A

phospholipids with hydrophlic heads and hydrophobic fatty acid tails (the lipid part is in the middle)

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3
Q

e.g. of intrinsic membrane proteins

A

ion channels, water channels, transporters, hormone receptors, cell surface antigens

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4
Q

intrinsic membrane proteins have _____ amino acid regions which are tucked within the alpha helix

A

hydrophlic

these are tucked inside since they are running through a hydrophobic region (the membrane)

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5
Q

movement in the bilayer (2 examples)

A

axial rotation

lateral diffusion

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6
Q

e.g. extrinsic/peripheral proteins

A

proteins of the cytoskeleton

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7
Q

extrinsic protein features

A

do not span the membrane

attachment occurs via ionic interactions to membrane phospholipids or intrinsic proteins

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8
Q

carbohydrates are on the ___ surface of the membrane

A

extracellular

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9
Q

role of monosaccharides on the PM

A

cell recognition/determining receptor specificity

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10
Q

passive transport: definition, examples

A

substance is transported down its electrochemical gradient and no energy is required
simple diffusion, facilitated diffusion

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11
Q

active transport: definition, examples

A

substance is transported against its electrochemical gradient and requires energy (ATP)
primary active transport, secondary active transport

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12
Q

all transport except for ____ needs a carrier molecule

A

simple diffusion

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13
Q

3 characteristics of carrier mediated transport

A

saturation
stereospecificity
competition

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14
Q

saturation

A

limited number of binding sites on carrier proteins (transport maximum or Tm)

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15
Q

which type of diffusion does not care about stereospecificity

A

simple diffusion

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16
Q

competition

A

structurally similar solutes compete for the same site

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17
Q

is simple diffusion saturable?

A

no

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18
Q

Km =

A

solute concentration which gives half the maximal transport rate

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19
Q

simple diffusion

A

non-carrier mediated transport down an electrochemical gradient

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20
Q

FLUX, J

A

the rate of net diffusion of solute molecules

the amount of solute moving across a unit area of membrane per unit of time

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21
Q

flux depends on 5 things

A
concentration gradient across the membrane
thickness of the membrane
lipid solubility of the solute
diffusion coefficient
permeability of a solute
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22
Q

oil water partition coefficient (K)

A

oil / water

the higher it is, the greater the lipid solubility

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23
Q

diffusion coefficient (D)

A

the larger the molecule and more viscous the medium, the lower the D

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24
Q

permeability

A

P = KD / membrane thickness

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25
Q

flux formula

A

J = P (C1-C2)

permeability constant * diff in conc of solute across the membrane

26
Q

in the flux equation, as long as C1 > C2, that means

A

there is net movement of solute from side 1 to side 2 of the PM

27
Q

once equilibrium has been reached, this is considered ___ ___ flux of solute

A

no net flux

28
Q

formula for the total amount of solute diffusing across an entire membrane into a cell

A

flux formula times the area of the membrane

= PA (C1-C2)

29
Q

the rate at which an uncharged solute (non-electrolyte) diffuses across the cell membrane is dictated by its ____ and _____

A

lipid solubility and molecular size

30
Q

are bigger or smaller molecules faster at diffusing through the PM?

A

smaller

31
Q

which form of a weak acid/base can diffuse across the membrane?

A

the un-dissociated form

they can get “trapped” if the pH changes and they dissociate

32
Q

facilitated diffusion

A

how lipid insoluble stuff gets across the membrane without using energy

33
Q

facilitated diffusion is different from simple diffusion b/c (4 things)

A
  • allows much more solute to be transported
  • is saturable
  • is solute specific
  • competition is involved
34
Q

ion channels (4 things)

A
  • passive (driven by electrochemical gradient)
  • regulated (channels open and close)
  • three magnitudes faster than facilitated diffusion
  • for electrical signaling and secretory processes
35
Q

facilitated diffusion is for the movement of

A

sugars and amino acids

36
Q

active transport

A

requires energy

moves things against a chemical or electrochemical gradient

37
Q

primary active transport

A

directly coupled to an energy producing reaction

i.e. sodium pump (Na/K ATPase)

38
Q

inhibitors of the sodium pump (2)

A

cardiac glycosides: ouabain and digoxin

these also inhibit secondary active transport

39
Q

for each molecule of ATP, ___ Na ions are pumped out and ____ K ions are pumped in

A

3 Na out

2 K in

40
Q

two other examples of primary active transport

A

Ca2+ ATPase - pumps Ca2+ out of cytoplasm

H+-K+ ATPase

41
Q

secondary active transport

A

NOT directly coupled to an energy producing reaction but instead depends on the primary active transport of sodium

42
Q

secondary active transport depends on the primary active transport of this ion

A

Na+

43
Q

there are two types of secondary active transport

A

1/ symport or co-transport

2/ antiport/countertransport/exchange

44
Q

symport/co-transport

A

all solutes move in the same direction across the cell membrane

the uphill solute moves in the same direction as sodium, so INTO THE CELL

45
Q

antiport/countertransport/exchange

A

uphill solute moves in the opposite direction to the sodium

sodium moves into the cell down its gradient
the solute here moves out of the cell AGAINST its gradient (the solute conc is high outside and low inside)

46
Q

aquaporins

A

the holes water travels through across a membrane

47
Q

osmosis

A

movement of water across a semi-permeable membrane as a result of the difference in the concentration of particles of a solute that is unable to pass across the membrane

water moves from the solution with the lowest to the solution with the highest concentration of particles

48
Q

_____ ______ is the driving force for osmosis

A

osmotic pressure

49
Q

in osmosis, the movement of water continues until the ____ pressure opposes the osmotic pressure

A

hydrostatic pressure (column of water)

50
Q

osmolarity

A

the number of solute particles present in a solution

51
Q

osmoles

A

= n x moles

n = number of particles from each molecule

52
Q

concentrated solutions have ____ osmolarity

A

higher

53
Q

concentrated solutions have ____ osmotic pressures than dilute solutions

A

higher

54
Q

water moves from ____ to _____ osmotic pressures across a semipermeable membrane

A

lower to higher

55
Q

osmotic pressure is proportional to _____ concentration

A

solute

56
Q

osmotic pressure depends on total _____ of the solution

A

osmolarity

57
Q

iso-osmotic solution

A

isotonic - no swelling or shrinkage occurs

58
Q

hypotonic solution

A

surrounding environment is less concentrated, so water swells into the more concentrated cell and swells it

(more dilute solutions cause bursting)

59
Q

hypertonic solution

A

surrounding environment is more concentrated, so water inside the cell rushes out, causing the cell to shrink and shrivel

60
Q

what happens to a cell when the sodium pump is not working?

A

Na+ is not pumped out, so water rushes in, causing the cell to swell