Powerpoint 3 Chapter 13

Question 1

active transport

Answer 1

pumps use energy to drive unfavorable transport

Question 2

passive transport

Answer 2

channels allow rapid thermodynamically favorable transport without use of energy

Question 3

membrane potential formula

Answer 3

dG=RTln(C2/C1) + ZFdV

Question 4

p-type

Answer 4

forms phospho-enzyme intermediate

Question 5

Na,K,ATPase transport per ATP

Answer 5

3 Na+ out, 2K+ in

Question 6

Na+ concentration in and out of cell

Answer 6

14 mM in, 143 mM out

Question 7

K+ concentration in and out of cell

Answer 7

10 mM out, 100mM in

Question 8

dG of ATP hydrolysis

Answer 8

-50 kJ /mol

Question 9

Ca++ ATPase

Answer 9

responisble for maintaining low Ca++ in muscle for relaxation. Located in sarcoplasmic reticulum. High conc in SR, low in cytoplasm.

Question 10

Ca++ ATPase structure

Answer 10

T domain binds two Ca++. N domain binds ATP. P domain contains Asp that is phosphorylated. A domain links them.

Question 11

high affinity Ca++binding state of Ca++ ATPase

Answer 11

without ATP bound

Question 12

inhibitor of Na+,K+,ATPase

Answer 12

foxglove (contains digitoxigenin, a caridotonic steroid)

Question 13

affect of Na+,K+,ATPase inhibition

Answer 13

increased Na+ in cell. slows down Na+,Ca++ anitporter. Increases Ca++ in heart muscle.

Question 14

flippases

Answer 14

facilitate membrane lipid asymmetry

Question 15

type 1 ABS transporters

Answer 15

in prokaryotes. import nutrients

Question 16

type 2 ABC transporters

Answer 16

in prokaryotes and eukaryotes. function as efflux pumps.

Question 17

MsbA

Answer 17

an ABC transporter that functions as a lipid exporter

Question 18

ABS transporter mechanism

Answer 18

open form, no ATP bound. substrate binds, induces conformational change allowing ATP to bind. ATP binds, conformational change allows substrate to other side of membrane. hydrolysis of ATP to reopen

Question 19

three types of secondary transport

Answer 19

symport, antiport, uniport

Question 20

uniporter

Answer 20

allows same molecule in or out of cell

Question 21

lactose permease

Answer 21

symporter that uses a pH gradient to drive uptake of lactose into cell

Question 22

mechanism of lactose permease

Answer 22

H+ binds from outside. lactose binds from outside. lactose deposited inside. H+deposited inside.

Question 23

membrane channels

Answer 23

use facilitated diffusion. are gated. have ion specificity

Question 24

membrane channels gates are turned on or off by (3)

Answer 24

ligands, membrane potential, mechanical means

Question 25

patch-clamp technique

Answer 25

used to measure ion flow through membrane using a glass pipette to form a seal on a patch of membrane. can observe single channels.

Question 26

sodium and calcium channel structure

Answer 26

four fold symmetry. Four repeating DNA sequences. Pore consisting of four identical subunits of two membrane spanning alpha-helices.

Question 27

structure of K+ channel

Answer 27

a K+ ion can travel 22A into the membrane until the path becomes too narrow (3A) and it must shed solvated water to pass. Carbonyl groups at the 3A pore specifically stabilize K+ through electrostatic interaction. K+ is pushed by incoming K+ through 4 binding sites of similar affinities within the 3A pore

Question 28

ion channels are similar to enzymes in that?

Answer 28

they lower the activation energy required for movement across the membrane

Question 29

why does the K+ channel reject passing of Na+ even though Na+ is smaller?

Answer 29

the carbonyl groups within the channel that aid in desolving ions out of water are positioned specifically for the stability of K+. The free energy of resolvation of Na+ in the channel is lower than the free energy of desolvation from water

Question 30

segments of K+ channel that form pore

Answer 30

S5 and S6

Question 31

voltage sensor segment of K+ channel

Answer 31

S4 positively charged helix

Question 32

action potential of Na and K channels

Answer 32

neurotransmitter causes flow of Na in and K out. Voltage sensing paddles of Na and K are pulled into membrane and rapid amount of Na flows in and K out until approaching Na equilibrium. Reversing polarity of membrane causes Na channel to close causing membrane potential to drop to K equilibrium at which point the K channel closes.

Question 33

ball-and-chain model for channel inactivation

Answer 33

tethered “ball” is floating in cytoplasm. Depolarization opens channel and creates binding site for ball. Binding of ball inactivates channel. Inactivated state returns to closed state spontaneously.

Question 34

Shaker K+ channel inactivation due to ?

Answer 34

N-terminal peptide

Question 35

? is the archetype of the ligand-gated ion channels

Answer 35

acetylcholine receptors

Question 36

nerve impulses are communicated across synapses by ?

Answer 36

neurotransmitters

Question 37

presynaptic and postsynaptic membrane separated by ?

Answer 37

synaptic cleft

Question 38

neurotransmitters contained in ?

Answer 38

synaptic vesicles

Question 39

acetylcholine receptor is a ? channel

Answer 39

ligand-gated

Question 40

purification of acetylcholine receptor occured in ?

Answer 40

torpedo memorota

Question 41

how acetylcholine receptor is purified

Answer 41

homogenize tissue with nonionic detergent. run extract over resin with covalently attached cobratoxin. elute bound protein.

Question 42

acetylcholine receptor structure

Answer 42

5 subunits. 2 alpha, 1 beta, gamma and delta subunits. Each subunit has 4 membrane spanning alpha-helices, extracellular beta strand region, and one alpha helix inside the cell.

Question 43

acetylcholine binding to acetylcholine receptor

Answer 43

binds to N-termini of alpha subunits at the a-d and a-g interface

Question 44

acetylcholine receptor response to binding

Answer 44

15 degree rotation in membrane spanning helix M2