EXAM 2 STUDY SET - CH 13

Question 1

Na+ — K+ ATPase

Answer 1

Active transport system.
P-Type ATPases.
Forms phosphorylated Asp intermediate.

Question 2

P-Type ATPases

Answer 2

couple phosphorylation and conformational changes to pump Ca2+ / H+ / Na+ ions, Cu2+ (metal), or phospholipids w/ charged head groups across membranes.

Question 3

P-Type ATPase Pump has what 2 conformations?

Answer 3

Ion binding site facing into cell.

Ion binding site facing out of cell.

Question 4

What powers the interconversion of the two conformations of the P-Type ATPase Pump?

Answer 4

ATP hydrolysis

Question 5

(SERCA) Sarcoplasmic Reticulum Ca2+ ATPase

Answer 5

pumps Ca2+ from muscle cytoplasm to sarcoplasmic reticulum.

Question 6

SERCA Structure

Answer 6

Single polypeptide chain w/ transmembrane domain - 10 α helices.

Question 7

SERCA binds?

Answer 7

Ca2+

Question 8

The cytoplasmic portion of SERCA contains what three domains?

Answer 8

N, P, A

Question 9

SERCA: N domain

Answer 9

binds ATP

Question 10

SERCA: P domain

Answer 10

Aspartate residue (Asp 351) accepts phosphate during rxn cycle.

Question 11

SERCA: A domain

Answer 11

links N and P domains.

Question 12

Catalytic Transport Cycle: P-Type ATPases

Answer 12

1. Bind cytoplasmic Ca.
2. ATP binding by N domain.
3. Transfer phosphoryl group to Asp in P domain.
4. ADP released, structural change, Ca binding site now faces sarcoplasmic reticulum lumen, Ca leaves enzyme.
5. Phosphoryl group in P domain hydrolyzed.
6. Enzyme changes conf. Ca binding site faces cytoplasm.

Question 13

P-Type ATPases Fundamental Rxn Mech

Answer 13

Free E release from ATP hydrolysis to drive membrane transport via conf. changes induced via addition / removal of phosphoryl group at key Asp site.

Question 14

ABC Transporters consist of what domains?

Answer 14

2 ABC domains

2 membrane-spanning domains.

Question 15

ABC Transporters are characterized by what common domain?

Answer 15

ATP-binding cassette (ABC)

Question 16

Multi-Drug Resistance protein (MDR)

Answer 16

ATP-dependent Pump.
Extrudes small molecules from cell.
ABC Transporter.

Question 17

ABC domains

Answer 17

ATP-binding domains

Question 18

ATP-binding Cassette Domain: Multi-Drug Resistance

Reaction Cycle:

Answer 18

1. Channel open to cytoplasm.
2. Substrates bind, conf. change in ABC domain.
3. ATP binds ABC domains, more structural changes, orient substrate to face outside of cell.
4. conf. has reduced affinity for substrate, allows release.
5. ATP hydrolysis - resets transporter to initial state.

Question 19

Lactose Permease

Answer 19

Secondary Transporter / Cotransporter.
Symporter.
Use one [gradient] to power formation of another.

Question 20

Symporter

Answer 20

Transport molecule against [gradient] by coupling movement w/ another molecule down its [gradient].
Substrates move in same direction.

Question 21

Antiporter

Answer 21

Use 1 [gradient] to power formation of another.

Transports 2 substrates in opp directions.

Question 22

Uniporter

Answer 22

Transport 1 substrate / molecule in either direction.

Depends on [difference] across membrane.

Question 23

Lactose Permease Mech

Answer 23

1. Lactose-binding pocket faces outside cell.
2. H+ binds, lactose binds.
3. Permease everts.
4. Lactose leaves permease.
5. H+ leaves permease, enters cell.
6. Permease everts, cycle complete.

Question 24

Ion Channels

Answer 24

allow rapid movement of ions across membranes down [gradient].

Question 25

Depolarization

Answer 25

+ change from resting potential. | Increased permeability to ion.

Question 26

What happens when the membrane potential is beyond the critical threshold value?

Answer 26

Depolarization. | Nerve impulse / AP gen'd.

Question 27

Action Potential

Answer 27

Result of K+ and Na+ channels opening / closing in response to changes in membrane potential. Signals sent along neurons by transient depolarization / repolarization.

Question 28

Repolarization

Answer 28

Internal charge returns to (-) value.

Question 29

Typical Membrane Resting Potential

Answer 29

-60mV | neuron interior higher [K+], lower [Na+] than exterior.

Question 30

K+ Ion Channel Structure

Answer 30

Four subunits - each homologous to one of repeated units in Na+ channel. 4 ion-binding sites.

Question 31

The Ca+ Channel is homologous to what other channel?

Answer 31

Na+

Question 32

Na+ Channel

Answer 32

4 repeated regions of similar seq. Each region: 5 hydrophobic segments. 1 hydrophilic segment.

Question 33

K+ Ion Channel Function

Answer 33

selectively, rapidly transports K+ along cell membrane.

Question 34

Why doesn't the K+ Ion Channel transport larger ions?

Answer 34

too big to enter channel

Question 35

Why doesn't the K+ Ion Channel transport smaller ions?

Answer 35

they can't interact w/ selectivity filter. | E of desolvation can't be compensated for by interactions w/ selectivity filter.

Question 36

Voltage-Gated Channels

Answer 36

Na+ and K+ Channels | Change conf. w/ changes in membrane potential.

Question 37

K+ Channel Segments

Answer 37

S1 - S4 function in voltage gating, "paddle" domains. Change in membrane potential alter conf. of paddles to open / close channel. S4 voltage sensor.

Question 38

Ball and Chain Model

Answer 38

Inactivates K+ Channel. | Ball tethered to channel via polypeptide segment (chain).

Question 39

Depolarization of the K+ Channel creates a?

Answer 39

binding site for ball, binds, inactivates channel.

Question 40

Acetylcholine

Answer 40

NT released into synaptic cleft.

Question 41

Acetylcholine binds to?

Answer 41

channel called acetylcholine receptor.

Question 42

When acetylcholine is bound to its receptor what happens?

Answer 42

Conf. changes. Rotate membrane-spinning helices. Opens K+ and Na+ channel (pore). Triggers AP.

Question 43

Acetylcholine Structure

Answer 43

4 subunits | α2βγδ arranged to form pentameric ring.

Question 44

Nernst Eqn

Answer 44

Equilibrium est'd - driving force of gradient countered by charge repulsion. membrane potential - equilibrium potential

Question 45

Action Potential (AP) Generation Mech

Answer 45

1. Activate acetylcholine receptor (K+ out, Na+ in). 2. membrane potential change activates Na+ Channels. 3. Subsequent opening of voltage-gated channels - "ball" of Na+ channel inactivates channel and acetylcholine receptor. 4. K+ channels open, membrane potential drops to K+ eq. potential 5. K+ channels closed by "ball" segment, membrane potential returns to initial state. 6. Events propagated down nerve membrane as AP.

Question 46

Electrocardiogram: P wave

Answer 46

Atrial myocardium depolarization. | Signals atrial contraction.

Question 47

Electrocardiogram: QRS Complex

Answer 47

Ventricular depolarization. Signals ventricular contraction. Simultaneous atria repolarization.

Question 48

Electrocardiogram: T wave

Answer 48

Ventricle repolarization. | Precedes ventricular relaxation.

Question 49

Electrocardiogram: PQ (PR) Interval

Answer 49

Atria contract, relax, ventricles contract. | .16 sec

Question 50

Electrocardiogram: QT Interval

Answer 50

Ventricles contract, begin to relax. | .36 sec

Question 51

Aquaporin

Answer 51

Allow rapid, specific water movement across membranes. | Increase permeability of some membranes to water.

Question 52

Aquaporin Structure

Answer 52

Hydrophilic residues line water channel.

Question 53

Ligand-Activated Channel

Answer 53

acetylcholine receptor

Question 54

Where does aquaporin exist?

Answer 54

``` Plasma membranes of kidneys. Liver. Eyes. GI Organs. Lungs. Glands. ```

Question 55

Diffusion

Answer 55

Movement of molecules from region of [high] to [low]. | Down [gradient]

Question 56

Gap Junction

Answer 56

Cell-to-cell channels. Passage of materials btw adj. cells. Intercellular communication. Polar molecules <1kDa can pass.

Question 57

Gap Junction Structure

Answer 57

``` 12 molecules of connexin 6 hexagonally arranged - form connexon. Connexon from adj. cells form gap juncton. Traverse 2 membranes. Cytoplasm-to-cytoplasm communication. ```