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BIOCH 320 > transport-1 > Flashcards

transport-1 Flashcards

1
Q

how do concentration gradients work

A

lead to solute transport predominantly towards the area of lower concentration (approaching equilibrium)

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2
Q

what happens if a charge separation exists across a membrane

A

it will create a transmembrane potential

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3
Q

what will create a transmembrane potential

A

if a charge separation exists across a membrane

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4
Q

what is an electrochemical gradient (what creates it)

A

combination of concentration and charge gradient

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5
Q

where will charged particles tend to move with electrical gradients

A

charged particles will move into the region of opposite charge

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6
Q

what does the C2 mean in

โˆ†๐‘ฎ๐‘ป = ๐‘๐“ ๐ฅ๐ง ๐‘ช๐Ÿ / ๐‘ช๐Ÿ
+ ๐’๐“•๐šซ๐

A

[A] destination

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7
Q

what does the C1 mean in

โˆ†๐‘ฎ๐‘ป = ๐‘๐“ ๐ฅ๐ง ๐‘ช๐Ÿ / ๐‘ช๐Ÿ
+ ๐’๐“•๐šซ๐

A

[A] origination

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8
Q

what does the Z mean in

โˆ†๐‘ฎ๐‘ป = ๐‘๐“ ๐ฅ๐ง ๐‘ช๐Ÿ / ๐‘ช๐Ÿ
+ ๐’๐“•๐šซ๐

A

ionic charge

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9
Q

what does the F mean in

โˆ†๐‘ฎ๐‘ป = ๐‘๐“ ๐ฅ๐ง ๐‘ช๐Ÿ / ๐‘ช๐Ÿ
+ ๐’๐“•๐šซ๐

A

faraday constant

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10
Q

what does the ๐šซ๐ mean in

โˆ†๐‘ฎ๐‘ป = ๐‘๐“ ๐ฅ๐ง ๐‘ช๐Ÿ / ๐‘ช๐Ÿ
+ ๐’๐“•๐šซ๐

A

membrane potential (usually -50mV)

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11
Q

do the calculation in the notes

A

okay

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12
Q

what does rate/kinetics across the membrane depend on

A

concentration of the molecules being transported and the nature of the transport process

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13
Q

how do small non polar molecules move across the membrane

A

diffuse freely (simple diffusion)

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14
Q

what do ionophores and channels do (simple)

A

allow molecules to move depending on concentration gradients

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15
Q

what do carriers do and what does the rate depend on

A

move molecules with a rate determined by both the gradients involved and the transporter kinetics (active and passive transporters)

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16
Q

what are the 2 main transporter types

A

passive and active

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17
Q

what do passive transporters do (what determines solute movement)

A

solute movement is determined by electrochemical gradient

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18
Q

what is the free energy of passive transporters

A

less than zero

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19
Q

what direction of movement happens with active transporters

A

movement of solute against the gradient

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20
Q

what is required in active transporters

A

energy input (coupled to exergonic process)

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21
Q

what is primary active transporter

A

exergonic chemical reaction

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22
Q

what is secondary active transporter

A

exergonic solute/ ion transport

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23
Q

what is the deltaG for active transport

A

less than zero

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24
Q

what is the deltaG solute/ion transport for secondary active transport

A

more than zero (its going against gradient)

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25
Q

what is the deltaG for other molecule secondary active transport

A

less than zero

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26
Q

what determines solute movement in passive transport

A

electrochemical gradient

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27
Q

what is delta GT for passive transport for the solute

A

less than zero for the solute

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28
Q

is passive transport specific

A

may be specific or non specific dependent on transport structure

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29
Q

what ultimately dictates direction of passive transport

A

solute

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30
Q

what ultimately dictates specificity of passive transport

A

transporter

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31
Q

what are ionophores

A

molecules that shuttle ions across membranes down their concentration gradient

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32
Q

what are 2 types of ionophores

A

carrier and channel

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33
Q

what are carrier ionophores like

A

they are undergoing motion back and force across membrane like a raft or ferry

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34
Q

what are channel ionophores like

A

more like tunnel or a bridge, create opening from one side to another

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35
Q

what are many ionophores like + how are they made

A

peptide or peptide like molecules produced by microorganisms

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36
Q

what do ionophores do to trans-membrane electrochemical gradients + what does this cause

A

it will destroy them, affecting secondary active transport processes

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37
Q

what do ionophores do to secondary active transport processes + why

A

affect them because it will destroy trans-membrane electrochemical gradients

38
Q

what class is valinomycin

A

a carrier ionophore

39
Q

what is valinomycin made from

A

neutral peptide-derived carrier ionophore

40
Q

what does valinomycin do (what is the mechanism)

A

six carbonyl groups will form a stable interaction with K+ ions
moves across the membrane

41
Q

what does valinomycin do as an ionophore (how does it work)

A

lipid-soluble (bound and unbound) and can move across the membrane

42
Q

is valinomycin toxic

A

it is potentially poisonous to any cell

43
Q

what does valinomycin bind

A

K+

44
Q

how many carbonyl groups in valinomycin

A

6

45
Q

what kind of phobicity happens with valinomycin

A

hydrophobic

46
Q

what linkages happen in valinomycin

A

a mix of ester and amide linkages

47
Q

what does valinomycin make coordination bonds with

A

water

48
Q

what is gramicidin

A

peptide based channel ionophores

49
Q

what are 3 types of gramicidin

A

A B C

50
Q

what are gramicidins A B and C + What structure do they form

A

linear peptide structures that form a beta helix structure

51
Q

what is the secondary structure like in gramicidin and why

A

beta-helix- unusual structure because of alternating L and D amino acids

52
Q

what creates the membrane-spanning channel in gramicidin

A

dimer

53
Q

what kind of ionophore is gramicidin (what cations)

A

monovalent cation ionophore (K+>Na+) -specific

54
Q

what is the primary structure of gramicidin

A

alternating L and D amino acids

55
Q

where do the side chains of gramicidin point

A

away from the helix core

56
Q

what is the hydrogen bond pattern like with gramicidin

A

beta sheet

57
Q

where do the side chains of valinomycin point

A

side chains point out

58
Q

where are aromatice residues like in gramicidin

A

clustered near the interface near the polar and non polar environment

59
Q

what are porins (what kind of secondary structure)

A

beta-barrel containing transmembrane proteins

60
Q

are porins selective

A

may be non selective (except for size) or selective for transported molecules

61
Q

are porins ion specific

A

no

62
Q

can anions go through porins

A

yes

63
Q

what kind of symmetry in lots of porins

A

C3

64
Q

can porins be dihedral and why

A

no because they usually have a very specific orientation, not like 1 up 1 down

65
Q

what symmetry in maltoporin

A

C3

66
Q

what kind of โ€œmerโ€ is maltoporin

A

homotrimer

67
Q

what kind of structure do maltoporin subunits have

A

18 stranded beta barrels

68
Q

what are the maltoporin openings like and where

A

in each subunit. left-handed curvature with an arrangement of non-polar/aromatic and polar residues

69
Q

what direction of beta barrel in maltoporin

A

anti-parallel

70
Q

what kind of chains can pass through maltoporin membrane

A

alpha1-4 linked linear chains

71
Q

why is maltoporin called a greasy slide

A

because there is partial hydrophobic areas

72
Q

what do ion-selective channels do

A

allow for rapid ion movement across a membrane

73
Q

what direction do ion selective channels do

A

down concentration gradient

74
Q

what is the rate of ion selective channels

A

rates approach free-diffusion limits

75
Q

are ion selective channels selective

A

highly

76
Q

are ion selective channels gated

A

they may be (opened or closed)

77
Q

what is a selectivity filter / what is it / how

A

channel functional groups that arrange to interact with very specific molecules

78
Q

what does selectivity filter determine

A

channel selectivity

79
Q

do ion selective channels change shape when things go through

A

no

80
Q

is there an upper limit with ion selective channels

A

no, its like free diffusion, no Vmax

81
Q

how many subunits in K+ channel in S. lividans

A

4

82
Q

what kind of symmetry in K+ channel in S. lividans

A

C4

83
Q

how many helices in K+ channel in S. lividans

A

2 transmembrane helices + additional alpha helix in core

84
Q

where is the K+ channel formed in K+ channel in S. lividans

A

between subunits - single channel passes from one side to the other of the bilayer

85
Q

where do K+ binding sites occur in K+ channel in S. lividans

A

series of K+ binding sites exist along the interface

86
Q

where is the selectivity filter in in K+ channel in S. lividans

A

mainly top part

87
Q

what charge are the openings in K+ channel in S. lividans

A

negatively charged

88
Q

where is the third helix in each subunits oriented in K+ channel in S. lividans

A

with its negative dipole towards the channel openings

89
Q

how many binding sites in the K+ channel in S. lividans

A

4 K+ binding sites in the channel

90
Q

what happens when new ions enter in K+ channel in S. lividans

A

the previously bound ions move further down the channel in alternating binding sites

91
Q

can Na+ interact in K+ channel in S. lividans + why

A

no because they are too small

92
Q

does the K+ channel in S. lividans change shape as K+ binds

A

no

BIOCH 320 (16 decks)

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