Talbot - Crossing the membrane: Protein Mediated Transport

Question 1

what are the 2 categories of protein-mediated transports

Answer 1

carriers and channels

Question 2

what happens to the solute in a carrier

Answer 2

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

Question 3

what happens to the solute in a channel

Answer 3

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

Question 4

what route is faster/more efficient in moving solutes

Answer 4

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

Question 5

what are the 3 types of carriers

Answer 5

uniport, symport and antiport

Question 6

what kind of transport is a uniport

Answer 6

transports 1 solute - either facilitated or primary active transport

Question 7

what kind of transport is a symport

Answer 7

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

Question 8

what kind of transport is a antiport

Answer 8

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

Question 9

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

Answer 9

active transport

Question 10

what are the 3 types of “solute carrier superfamily”

Answer 10

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

Question 11

what does a transporter do

Answer 11

same as uniporter

Question 12

what does a cotransporter do

Answer 12

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

Question 13

what does an exchanger do

Answer 13

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

Question 14

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

Answer 14

sensing actual membrane potential (voltage sensors)

Question 15

what is the 6th helix involved in the ion channels

Answer 15

may line the transmembrane pore

Question 16

what are the 4 types of ion channel gates

Answer 16

1. ligand gated
2. phosphorylation gated
3. voltage gated
4. mechanically gated

Question 17

how does a ligand gated channel work

Answer 17

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

Question 18

how does a phosphorylation gated channel work

Answer 18

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

Question 19

how does a voltage gated channel work

Answer 19

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

Question 20

how does a mechanically gated channel work

Answer 20

by stretching or pressure

Question 21

what is passive transport

Answer 21

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

Question 22

what is primary active transport

Answer 22

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

Question 23

how does the primary active transport get ATP for energy

Answer 23

transport protein directly hydrolyzes ATP for energy

Question 24

what are 3 classes of transport ATPases

Answer 24

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

Question 25

Will a drug that inhibits ATP production affect secondary active trasnport

Answer 25

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

Question 26

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

Answer 26

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

Question 27

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

Answer 27

ouabain and other cardiac glycosaides

Question 28

what is secondary active transport

Answer 28

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

Question 29

what type of transporter is secondary active transport

Answer 29

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

Question 30

what is the P-type of ATPase pumps

Answer 30

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

Question 31

what are some examples of a P-type pump

Answer 31

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

Question 32

what is the F-type pump

Answer 32

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

Question 33

which direction do the F-type proton pumps work

Answer 33

backwards and function as ATP synthases

Question 34

where are the V-type pumps found

Answer 34

(vacular) in organelle membranes: some epithelia and lysosomes

Question 35

how do V-type pumps work

Answer 35

use ATP to pump H+ against its gradient

Question 36

what are ABC transporter pumps

Answer 36

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

Question 37

how do ABC transporters work

Answer 37

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

Question 38

what are membrane domains

Answer 38

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

Question 39

how many domains do epithelial cells have

Answer 39

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

Question 40

what are the 2 membrane domains of the epithelial cell

Answer 40

apical/luminal/mucosal membrane and basolateral membrane

Question 41

how does an epithelial cell absorb sodium

Answer 41

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+

Question 42

how does an epithelial cell absorb NaCl

Answer 42

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

Question 43

how does an epithelial cell absorb glucose

Answer 43

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

Question 44

how does an epithelial cell secrete chloride

Answer 44

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

Question 45

where are tight junctions located in epithelial cells

Answer 45

separating the apical and basolateral membranes

Question 46

what is the function of the tight junctions

Answer 46

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

Question 47

where are gap junctions in epithelial cells

Answer 47

connect cytoplasm between adjacent cells and allows direct communication

Question 48

what makes up the structure of a gap junction

Answer 48

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

Question 49

what are 2 ways water can move through a cell

Answer 49

both passive: simple diffusion or AQP (aquaporin) channels

Question 50

what is acute hypertonicity

Answer 50

cells shrink in a hypertonic environment (water loss)

Question 51

what does shrinkage of the cell induce

Answer 51

a regulatory volume increase (RVI)

Question 52

what 2 things are stimulated in a hypertonic environment

Answer 52

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

Question 53

what does swelling of the cell induce

Answer 53

a regulatory volume decrease (RVD)

Question 54

what channels are stimulated in a hypotonic environment

Answer 54

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