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MCBM Part 1 > Talbot - Crossing the membrane: Protein Mediated Transport > Flashcards

Talbot - Crossing the membrane: Protein Mediated Transport Flashcards

1
Q

what are the 2 categories of protein-mediated transports

A

carriers and channels

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2
Q

what happens to the solute in a carrier

A

after the solute binds to the protein it causes it to change conformation in order to move the solute

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3
Q

what happens to the solute in a channel

A

it moves through aqueous pose in membrane and only interacts weakly with channel proteins

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4
Q

what route is faster/more efficient in moving solutes

A

channels - they do not have to open each time a solute comes along

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5
Q

what are the 3 types of carriers

A

uniport, symport and antiport

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6
Q

what kind of transport is a uniport

A

transports 1 solute - either facilitated or primary active transport

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7
Q

what kind of transport is a symport

A

2+ solutes in the same direction - coupled transport (primary or secondary active transport)

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8
Q

what kind of transport is a antiport

A

2+ solutes in opposite directions - coupled transport (primary or secondary transport)

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9
Q

what type of pump has “ATPase or pump” in the name

A

active transport

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10
Q

what are the 3 types of “solute carrier superfamily”

A

they do not hydrolyze ATP or couple to an electron transport chain - transporter, cotransporter, and exchanger

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11
Q

what does a transporter do

A

same as uniporter

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12
Q

what does a cotransporter do

A

same as symporter: solutes are going in same direction (primarily into cell) and usually has a / between solutes in name

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13
Q

what does an exchanger do

A

same as antiport: usually has a - between solutes in name

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14
Q

what is the 4th helix involved with in the ion channels

A

sensing actual membrane potential (voltage sensors)

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15
Q

what is the 6th helix involved in the ion channels

A

may line the transmembrane pore

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16
Q

what are the 4 types of ion channel gates

A
  1. ligand gated
  2. phosphorylation gated
  3. voltage gated
  4. mechanically gated
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17
Q

how does a ligand gated channel work

A

(ligand = signal molecule) either a neurotransmitter or hormone that binds non-covalently to receptor domain

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18
Q

how does a phosphorylation gated channel work

A

channel is phosphorylated and remains open as long as PO4- group is attached

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19
Q

how does a voltage gated channel work

A

change in membrane potential opens gate (excitable cells like neurons and muscle fibers)

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20
Q

how does a mechanically gated channel work

A

by stretching or pressure

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21
Q

what is passive transport

A

solute moves down its (electro) chemical gradient (ex. channels and carriers)

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22
Q

what is primary active transport

A

uses cellular energy (ATP) to drive solutes against (electro) chemical gradient (ex. uniports or coupled transport, “pumps/ARPases)

23
Q

how does the primary active transport get ATP for energy

A

transport protein directly hydrolyzes ATP for energy

24
Q

what are 3 classes of transport ATPases

A

P-Type, F-Type (related V-type), and ABC transporters

25
Q

Will a drug that inhibits ATP production affect secondary active trasnport

A

yes - it will first inhibit primary active transport and then inhibit secondary by stopping the potential gradient across membrane from changing

26
Q

how many Na+ and K+ are transported in a Na+/K+ ATPase pump antiport

A

3 Na+ out of cell and 2 K+ into cell

27
Q

what type of drug blocks a Na+/K+ ATPase pump

A

ouabain and other cardiac glycosaides

28
Q

what is secondary active transport

A

uses potential energy stored in ion gradient to drive active transport of a different solute

29
Q

what type of transporter is secondary active transport

A

always coupled transporters (non-ATP driven) -> cotransporters or exchangers (symport or antiport)

30
Q

what is the P-type of ATPase pumps

A

pumps proteins that are phosphorylated by autophosphorylation of transport protein (induces a conformational change)

31
Q

what are some examples of a P-type pump

A

cation pumps, phospholipid flippases, Na+/K+ ATPase, SERCA (sarco-endoplasmic reticulum Ca++ pump)

32
Q

what is the F-type pump

A

transports protons- ATP synthase is used to generate ATP energy from moving proton across inner mitochondrial membrane

33
Q

which direction do the F-type proton pumps work

A

backwards and function as ATP synthases

34
Q

where are the V-type pumps found

A

(vacular) in organelle membranes: some epithelia and lysosomes

35
Q

how do V-type pumps work

A

use ATP to pump H+ against its gradient

36
Q

what are ABC transporter pumps

A

ATP-binding cassette transporters - to pump solutes other than ions out of cytoplasm

37
Q

how do ABC transporters work

A

have 2 ATP binding domains - ATP binding and hydrolysis induces conformational changes

38
Q

what are membrane domains

A

specific proteins that allow region of cell to have a unique function

39
Q

how many domains do epithelial cells have

A

2 distinct membrane domains that contain proteins specific to given roles “polarized cells”

40
Q

what are the 2 membrane domains of the epithelial cell

A

apical/luminal/mucosal membrane and basolateral membrane

41
Q

how does an epithelial cell absorb sodium

A

epithelial Na channels (ENaC) in apical membrane allow Na+ to enter and Na/K ATPase completes in basolateral membrane complete transepithelial sodium flux, also has a K+ channel to recycle K+

42
Q

how does an epithelial cell absorb NaCl

A

there is a Na/H exchanger (NHE) and anion exchanger (AE) on apical membrane that exchange Cl- for HCO3- and a basolateral KCC to transport Cl- out of cell

43
Q

how does an epithelial cell absorb glucose

A

it moves across cell coupled with sodium (secondary active transport) and basolateral membrane has a glucose uniport for facilitated diffusion out of cell

44
Q

how does an epithelial cell secrete chloride

A

NKCC secondarily actively transports chlorine into cell on basolateral membrane and CFTR (Cl- channel in apical membrane) for movement out of cell

45
Q

where are tight junctions located in epithelial cells

A

separating the apical and basolateral membranes

46
Q

what is the function of the tight junctions

A

prevent/minimize paracellular movement of solutes and maintain polarity of the cell

47
Q

where are gap junctions in epithelial cells

A

connect cytoplasm between adjacent cells and allows direct communication

48
Q

what makes up the structure of a gap junction

A

6 connexins = 1 connexon (the actual pore structure) then the connexons line up into channels

49
Q

what are 2 ways water can move through a cell

A

both passive: simple diffusion or AQP (aquaporin) channels

50
Q

what is acute hypertonicity

A

cells shrink in a hypertonic environment (water loss)

51
Q

what does shrinkage of the cell induce

A

a regulatory volume increase (RVI)

52
Q

what 2 things are stimulated in a hypertonic environment

A

NKCC and Na/H (NHE) exchange are stimulated = bringing Na, K, and Cl into cell and alkalize the pH

53
Q

what does swelling of the cell induce

A

a regulatory volume decrease (RVD)

54
Q

what channels are stimulated in a hypotonic environment

A

K+ and Cl- are opened and in some cases KCC cotransporter will transport Cl- out of cell with K+ have H2O follow

MCBM Part 1 (29 decks)

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