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BIOCH 320 > transport-2 > Flashcards

transport-2 Flashcards

1
Q

what kind of channel is the chloride channel in S. typhimurium

A

anion

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2
Q

where are the channels in the chloride channel in S. typhimurium

A

through the center of each subunit, not at interfrace

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3
Q

what kind of “mer: structure in the chloride channel in S. typhimurium

A

homodimer

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4
Q

how many helices in the chloride channel in S. typhimurium + how are they oriented

A

18 transmembrane alpha helices, tilted relative to membrane

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5
Q

what creates the selectivity filter in the chloride channel in S. typhimurium

A

alpha helices (N terminal dipole) and OH containing amino acids(Ser tyr)

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6
Q

are there positive in the chloride channel in S. typhimurium and why

A

no because then the anion will just stick to it

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7
Q

what do aquaporins do

A

allow for cross-membrane movement of water, excluding other solutes and H+ (H3O+)

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8
Q

what kind of “mer” are aquaporins

A

homotetramer

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9
Q

what kind of helices in aquaporins

A

multiple transmembrane alpha helices

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10
Q

where are water channels formed in aqua porins

A

at the center of each subunit

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11
Q

what is the symmetry in aqua porins

A

C4

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12
Q

what kind of “mer” are Cl- channels

A

dimer

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13
Q

what kind of “mer” are K+ channels

A

tetra

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14
Q

where are channels formed in K+

A

between subunits

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15
Q

where are channels formed in Cl-

A

within subunits

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16
Q

are K+ channels polytopic helical bundles

A

yes

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17
Q

are Cl- channels polytopic helical bundles

A

yes

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18
Q

what is the movement in aquaporis like

A

proton movement via proton jumping is prevented by Hbonding interactions in the channel

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19
Q

what prevents proton jumping in aquaporins

A

H bonding interactions in the channel

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20
Q

what does GLUT1 do/what is it

A

passive carrier for D-glucose

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21
Q

how many helices in GLUT1

A

12 transmembrane

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22
Q

what do lots of the transmembrane helices contain in GLUT1

A

polar amino acids

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23
Q

is GLUT1 polytopic

A

yes

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24
Q

how many domains in GLUT1 and what are they like

A

2 domains with 6helices each

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25
Q

how many aa per turn in helix

A

3.6

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26
Q

what phobicity are transmembrane alpha helices generally

A

hydrophobic

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27
Q

where is the binding site of the solute usually

A

midway through membrane

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28
Q

what are the arrangement of amino acids in amphipathic helices

A

polar and non polar on opposite faces

  • non polar towards lipid core
  • polar towards inside of passage through the center
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29
Q

where will non polar regions be in amphipathic helices

A

oriented towards the lipid core

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30
Q

where will polar regions be in amphipathic helices

A

in the center to create a polar passage

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31
Q

does GLUT1 have continuous passage from one side of the membrane to the other and why

A

no because its a carrier

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32
Q

what does binding of glucose to GLUT1 cause

A

conformational shift leading to binding site being opened to the interior

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33
Q

what is GLUT1 transport dependent on

A

rate of steps in the process (kinetics of binding and conformational rearrangement)

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34
Q

what is rate of transport in carries analogous to

A

michaelis menten enzyme kinetics (similar equation)

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35
Q

what is Kt

A

concentration of colute where Vo=0.5Vmax

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36
Q

what is K1 for GLUT1 compared to blood glucose levels

A

K1 is smaller

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37
Q

what does Kt reflect with specificity and GLUT1

A

specific interactions between the carrier and the OH groups in D-glucose

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38
Q

is Kt bigger or smaller with L or D glucose

A

bigger with L glucose by a lot

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39
Q

do calculation question

A

okie

40
Q

what drives active transport

A

electrochemical gradient

41
Q

what are the Gt an Gnet for active transport

A

Gt>0 for at least 1 solute

Gnet< 0 for transport

42
Q

what does negative free energy come from in primary active transport

A

chemical reaction

43
Q

what does negative free energy come from in secondary active transport

A

another solute

44
Q

what kind of transport is ATPase

A

primary active transporters

45
Q

how do ATPases work

A

hydrolysis of ATP provides energy to move solutes up concentration gradients

46
Q

what kind of conformational changes with ATPases

A

reversible conformational changes with phosphorylation and dephosphorylation

47
Q

are flippases P-type ATPases

A

yes

48
Q

what does SERCA stand for

A

sarcoplasmic and endoplasmic reticulum calcium pumps

49
Q

what type of ATPase is SERCA pump

A

P-type ATPase

50
Q

what is the role of SERCA pumps

A

transport of Ca++ our of cytoplasm and into sarcoplasmic reticulim during muscle relaxation

51
Q

are floppases P-type ATPases

A

no

52
Q

how many domains in SERCA pump

A

4

53
Q

what are the dimains in SERCA pump

A

M-transmembrane
P-phosphorylation
N-nucleotide binding
A-actuator

54
Q

how many polypeptides in SERCA pump

A

1

55
Q

is SERCA pump multipass

A

yes

56
Q

what is the E1 domain in SERCA pump (where open to)

A

cytoplasmic face

57
Q

what is the E2 domain in SERCA pump (where open to)

A

open to exoplasmic face

58
Q

what is the M domain in SERCA pump like +where is it

A

10 transmembrane helices with 2 Ca++ binding sites near center

59
Q

what is the N domain in SERCA pump like +where is it

A

cytosolic, ATP binding site

60
Q

what is the P domain in SERCA pump like +where is it

A

cytosolic, asp side-chain phosphorylated by ATP induces conformational change in M Domain

61
Q

what is the A domain in SERCA pump like +where is it

A

cytosolic, connects confomational changes in N and P domains to M domain

62
Q

which residue is phosphorylated by ATP In SERCA pump and which domain

  • what does it become
A

asp in P domain

asparyl phosphate

63
Q

what affinity is the E1 conformation in SERCA + where

A

high Ca++ affinity in cytosol

64
Q

what affinity is the E2 conformation in SERCA + where

A

low Ca++ affinity in lumen

65
Q

is the phosphorylation site close to the Ca++ binding site in SERCA

A

no

66
Q

what state is SERCA in when phosphorylated

A

E1 to E2

67
Q

what state is SERCA in when unphosphorylated

A

E2 to E1

68
Q

what is the major facilitator superfamily

A

multiple families of transporters with relatively low sequence similar but similar predicted topologies

69
Q

what organism classes have major facilitator superfamily

A

bacteria archaea eukarya

70
Q

how many peptides in major facilitator superfamily + what do they form

A

single (multipass, helical bundes)

71
Q

how many helices and what do they form in major facilitator superfamily

A

12-14 helices in 2 semi-symmetrical pairs of 6 or 7 helices

72
Q

what are 2 examples of major facilitator superfamily

A

lactose transporter and GLUT1

73
Q

what is Kd for calcium bindinf in E1 vs E2 for SERCA

A

Kd(E1)

74
Q

what kind of transporter is the lactose transporter

A

2ary active transport

75
Q

what kind of gradient happens in the lactose transporter + which direction

A

proton gradient is higher on outside than in

76
Q

what direction does the lactose transporter run

A

proton taken down gradient to bring lactose its gradient

77
Q

what is the E1 for lactose transporter

A

E1 open to cytoplasmic face

78
Q

what is the E2 for lactose transporter

A

E2 when open to periplasmic face

79
Q

what maintains the proton gradient in lactose transporter

A

proton pumps

80
Q

what is affinity for E1 in lactose transporter

A

low affinity

81
Q

what is affinity for E2 in lactose transporter

A

high affinity

82
Q

which E does lactose bind to and where is it

A

E2 outside the cytoplasm

83
Q

which E does lactose release from and where is it

A

E1 inside the cytoplasm

84
Q

where does lactose bind in lactose permease

A

between domains near the center

85
Q

how many binding sites for lactose

A

1

86
Q

how many amino acids in lactose permease

A

417

87
Q

how many polypeptides in lactose permease

A

1

88
Q

how many helices in lactose permease

A

12 transmembrane

89
Q

how many domains in lactose permease

A

2

90
Q

what is the lactose permease mechanism

A

binding of lactose and protonation of specific residues in transporter drives a conformational shift
-the domains rock, opening binding site to interior where both lactose and proton dissociate

91
Q

what happens if you disrupt the proton gradient or mutations to lactose carrier

A

it can make it a passive carrier

92
Q

what is a way to inhibit the proton pump in lactose

A

by CN-

93
Q

what does CN- do to lactose transporter

A

inhibits proton pump and leads to lactose export

lactose transport down its concentration gradient

94
Q

what does glu or arg mutation in lactose transporter do

A

uncouples lactose import from the proton gradient

lactose transport down its concentration gradient

95
Q

what determines lactose transport limit

A

the relative concentration of lactose across the membrane (not saturation!)

BIOCH 320 (16 decks)

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