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BMSC 200 > module 9: Membranes > Flashcards

module 9: Membranes Flashcards

1
Q

what does the membrane structure formation depend on?

A

ratio of cross-sectional areas of the polar head group and hydrophobic tail

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2
Q

what do fatty acids favour?

A

formation of micelles

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3
Q

what 2 lipids tend to form bilayers?

A

glyceophospholipids & sphingolipids

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4
Q

what are membranes primary made of?

A

lipids and proteins

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5
Q

do more active membranes have a higher or lower ratio of protein to lipid?

A

higher

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6
Q

why are membranes dynamic?

A

because of non-covalent interactions

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7
Q

what is flip flop diffusion?

A

slow uncatalyzed rate of lipid molecule crossing from 1 sheet to another

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8
Q

what are the enzymes called that translocation of lipids across membranes

A

flippases

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9
Q

what is the function of flippases?

A

provide environment so lipids can go through

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10
Q

what happens below the phase transition temp?

A

membrane is too solid

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11
Q

what happens above the phase transition temp?

A

membrane is too fluid

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12
Q

what happens at the phase transition temp?

A

hydrocarbon chains are partially ordered but lateral

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13
Q

why are lipid rafts formed?

A

to optimize interactions between hydrocarbon tails of membrane lipids

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14
Q

what proteins perform active roles in membranes?

A

receptors & transporters

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15
Q

how do peripheral membrane proteins associate with the membrane?

A

through electrostatic or hydrogen-bonding interactions

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16
Q

where are peripheral membranes found?

A

in cytosol or extracellular space

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17
Q

are peripheral membrane proteins strong or weak?

A

weak

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18
Q

where are GPI anchored proteins found on the membrane?

A

outer face

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19
Q

where are integral membrane proteins found?

A

immersed & span the membrane

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20
Q

where are charged amino acids found in the membrane?

A

intracellular & extracellular portions of the proteins

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21
Q

where are amino acids with non-polar side chains found in the membrane?

A

inside the hydrophobic slab of bilayer

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22
Q

where do tryptophan & tyrosine cluster on the membrane?

A

interface between the hydrocarbon chain & polar head region

23
Q

how can membrane spanning regions be predicted?

A

amino acid sequence

24
Q

how many hydrophobic membranes in a row are membrane spanning?

A

20-24

25
Q

what does the hydropathy index look at?

A

the hydrophobic characteristics of a protein to predict transmembrane regions

26
Q

side chains within the transmembrane region tend to be…

A

non-polar, but carbonyl & amide groups are polar

27
Q

what groups are energetically unfavourable in the bilayer core?

A

polar, unpaired carbonyl & amide groups

28
Q

what is simple diffusion?

A

non-polar gases (O2 & CO2) and hydrophobic molecules can directly cross the membrane

29
Q

what is facilitated diffusion?

A

membrane transporters lower the activation energy barrier to cross the bilayer

30
Q

what is facilitated diffusion through channels?

A

membrane pores that allow transport of molecules down the concentration gradient

31
Q

are channels or carriers faster?

A

channels

32
Q

do channels or carriers saturate?

A

carriers

33
Q

what is facilitated diffusion through carriers?

A

membrane proteins undergo substrate induced confirmation change to release substrate to other side of membrane

34
Q

uptake of glucose into red blood cells is an example of which type of diffusion?

A

facilitated diffusion through a carrier

35
Q

what is uniport?

A

transport of a single molecule

36
Q

what are antiporters?

A

move molecules in different directions

37
Q

what are symporters?

A

move molecules in the same direction

38
Q

what does co-transport through antiport or symport depend on?

A

the charge of the molecule

39
Q

what happens in secondary active co-transport?

A

system couples a molecule moving down its gradient to another one moving down its gradient

40
Q

what is active transport?

A

input of energy that allows movement of molecules against concentration gradients

41
Q

what is primary active transport?

A

driven by direct source of ATP & establishes a gradient for secondary active transport to use

42
Q

what is secondary active transport?

A

couples the movement of one molecule down its gradient within the movement of another molecule down its gradient

43
Q

what does P-Type ATPase use for active transport?

A

antiport

44
Q

cells maintain high gradients of ( ) outside the cell and ( ) inside the cell

A

Na+ outside, K+ inside

45
Q

Why is it called a P-type transporter?

A

bc it undergoes a phosphorylated intermediate

46
Q

what is pumped in/out of the cell during P-type ATPase primary active transport?

A

pumps 3 Na out & 2 K + in

47
Q

what is V-type ATPases active transport?

A

uses energy of ATP to move protons against a concentration gradient

48
Q

what are ABC transporters?

A

contain ATP binding domains (ATP-Binding-Cassette)

49
Q

what do ABC transporters do?

A

transport a variety of biomolecules out of the cell against a concentration gradient

50
Q

glucose uptake into intestinal epithelial cells is an example of which type of transport?

A

secondary active transport

51
Q

glucose uptake into intestinal epithelial cells is uniport, antiport or symport?

A

symport

52
Q

what is the function of ion channels?

A

enable rapid movement of ions across membranes

53
Q

action of ion channels can cause…

A

action potentials

54
Q

function of the K+ ion channel

A

allows rapid movement of K+ ions out of the cell

BMSC 200 (10 decks)

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