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Membranes > Jeuken > Flashcards

Jeuken Flashcards

1
Q

How is water transported into a cell?

A

down 55M gradient by free diffusion or facilitated diffusion through aquaporins

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2
Q

for simple diffusion: -Gibbs can be what kind of movement regarding electrochemical or concentration gradient?

A

down concentration gradient or up concentration gradient if down electrochemical gradient

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3
Q

what substances can move by free diffusion?

A

lipophiles and gases dissolved in solvents

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4
Q

what is partition?

A

hydrophobicity

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5
Q

aminos-sugars-aliphatics have _ _creasing permeability and hydrophobicity

A

increasing

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6
Q

what are the 4 types of protein transporters?

A

Ion channels, ATP powered pumps, transporters, pores

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7
Q

How many strands make up a beta-barrel

A

8-22 strands, mostly homotrimers of 16-18 strands

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8
Q

beta-barrels are used for what tpe of transport

A

pores for simple diffusion

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9
Q

ompX is a beta barrel for what function?

A

membrane bound adhesion receptor

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10
Q

lipocalin retinoid receptor is what type of protein?

A

soluble beta-barrel

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11
Q

which residues are exposed at beta-barrel faces?

A

~40% aromatics interact with phospholipids

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12
Q

where are TM beta barrel pores found?

A

mitochondria, chloroplast, gram negative bacteria

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13
Q

what do Omp proteins do?

A

pores in E.coli with weak cation selectivity provided by acidic residues in the filter.

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14
Q

what are the examples of b-barrel pores?

A

PhoE, Omp, Lamb, FepA&FhuA

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15
Q

What are the 2 types of simple diffusion proteins?

A

Gap junctions, beta barrels

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16
Q

what is the structure of a gap junction?

A

6 subunits x 4TM alpha helices. Phosphorylation regulates opening, connexin mixtures regulate pore size

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17
Q

What are the 4 classes of ATP powered pumps?

A

P, V, F ATPases; ABC

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18
Q

what energy drives active transport?

A

Voltage gradient or ATP

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19
Q

what is the structure of P class ATPases?

A

2 independent, identical alpha subunits containing pump, Aspartate for phosphorylation and ATP binding domain.

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20
Q

What is the mechanism of active transport proteins?

A

Alternating access driven by ATP hydrolysis and phosphorylation altering conformation and substrate affinity.

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21
Q

What is the structure of ABC transporters?

A

1-4 peptides with 2 cytoplasmic NDB, 2 TM domains totalling 6 helices up, 6 helices down.

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22
Q

What are examples of ABC transporters?

A

Mdr1 (multi drug),
MalK (maltose),
CFTR,
BtuC (Vitamin B12)

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23
Q

Which proteins mediate facilitated transport?

A

ion channels, uniports, symports, antiports.

24
Q

What is the structure of passive transporters?

A

12 TM inverted repeat with substrate binding pocket

25
Q

what is the mechanism of passive transporters?

A

occlusion alternate access

26
Q

what are examples of passive transporters?

A

Glut1 (glucose uniport),
XylE (D xylose, H+ symport),
Mph1 (hydantion Na+/H+ symport)
BetP (betaine with choline antiport or Na+ symport)

27
Q

where are GLUT1 transporters?

A

RBC and BBB.

28
Q

what disease is associated with GLUT1 mutations?

A

de vivo neurological disorder

29
Q

Where are GLUT4 transporters?

A

uniporters into muscle cells expressed on insulin stimulation

30
Q

Where is SGLT1?

A

Na+ symport from gut, gradient maintained by Na/K pumo

31
Q

Where is SGLT2?

A

reabsorption from kidney

32
Q

what are the 5 families of multidrug resistance efflux pumps?

A 
ABC uniports
MATE Na+ antiport
MFS H+ antiport
SMR H+ antiport
RND
33
Q

where are drug efflux pumps found?

A

bacterial membrane, coupled to TolC in Gram negative

34
Q

What type of transport do ion channels mediate?

A

specific but passive

35
Q

Where are ion channels found?

A

All kingdoms

36
Q

what is the structure of ion channels?

A

4 subunits x 6TM helices + P loop for selectivity filter

37
Q

What does KcsA transport?

A

K+ in hydrated state

38
Q

what is the structure of KcsA?

A

4 subunits x 2TM helices with P loop coordinating TVGYG selectivity filter which binds 2K using oxygen to coordinate

39
Q

how many K does KcsA transport?

A

3: 2 in selectivity filter and a hydrated one in channel

40
Q

What is the structure of the Kv1.2 channel?

A

4 subunits x 6TM helices and P loop.
250 residue N terminal, 150 residue C terminal domain
4Arg sensor in helix 4
Glycine hinge in helix 6 opens channel

41
Q

how is the Kv1.2 channel spontaneously inactivated?

A

intrinsically disordered N terminal ball has 10 residues to enter channel and 10 residues for hydrophilic T1 domain

42
Q

Where is Kv1.2 found?

A

eukaryotes for action potential

43
Q

What signalling is NavAB channel used in?

A

nociception

44
Q

what 3 forms does NavAB exist in?

A

closed, pre-open (helix 5 gating hinge open), open (glycine hinge open)

45
Q

What are TRP channels?

A

weakly selective cation transporters involved in senses

46
Q

what structure do TRP channels have?

A

tetramers of 6 TM helices but low homology to v-gated channels.

47
Q

what are the 7 TRP families?

A

C,V,M,A,ML,P,N

48
Q

which TRP channel is involved in taste?

A

M5

49
Q

What does M5 TRP channel detect?

A

Calcium released from ER by GPCR opens channel for depolarisation by Na influx.
Also detects voltage and temperature.

50
Q

which neurons do TRP receptors integrate into?

A

Trigemal and dorsal root ganglions

51
Q

Which TRP channel detects hot substances?

A

V1

52
Q

Which TRP channel detects cool substances?

A

M8

53
Q

Which TRP channel detects pungent substances?

A

A1

54
Q

Which TRP channel is selective for Ca?

A

A1

55
Q

Which TRP channel detects inflammation?

A

A1, V1

56
Q

Why is CTFR unusual?

A

homology based ABC structure of 2NBD and 2TM inverted repeat BUT ION CHANNEL

57
Q

How does ATP act on CFTR?

A

R domain phosphorylation increases affinity for Cl- substrate by bringing NBDs together.

Membranes (7 decks)

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