Lecture 17 + 18, Transport Proteins (Ford)

Question 1

List the 2 methods to cross a membrane.

Answer 1

Active or passive transport

Question 2

Describe passive transport.

Answer 2

No energy needed, solute travels down concentration gradient

Question 3

Describe active transport.

Answer 3

Coupled to ATP hydrolysis, solute travels against concentration gradient

Question 4

What are the 3 general modes of transport across a membrane?

Answer 4

Antiport, synport, uniport

Question 5

List the 3 general categories of transporters.

Answer 5

Pumps, carriers, channels

Question 6

Describe pumps.

Answer 6

Perform primary active transport

Question 7

Describe carriers.

Answer 7

Traverse membrane without needing extra energy

Question 8

Describe channels.

Answer 8

Used in passive transport

Question 9

T or F: P-type pumps phosphorylate themselves.

Answer 9

True.

Question 10

T or F: V-type proton pumps make ATP.

Answer 10

False. V-type proton pumps use ATP, while F-type ATP synthase makes ATP.

Question 11

What are the 4 domains of P-type ATPases?

Answer 11

Transmembrane domain, actuator domain, nucleotide binding domain, phosphorylation domain

Question 12

T or F: The transmembrane domain of a P-type ATPase spans the lipid bilayer.

Answer 12

True.

Question 13

Describe the actuator domain of a P-type ATPase.

Answer 13

Links cytosolic domains to the transmembrane domain

Question 14

Which domain of the P-type ATPase binds ATP?

Answer 14

Nucleotide binding domain

Question 15

Which domain of the P-type ATPase accepts the phosphate from ATP?

Answer 15

Phosphorylation domain

Question 16

Outline the action of SERCA.

Answer 16

1. E1 unphosphorylated, Ca++ ions bound
2. ATP binds, Ca++ ions trapped
3. ATP hydrolysis, self phosphorylation
4. Eversion to E2, Ca++ ions released
5. Release of Pi
6. Eversion to E1

Question 17

T or F: The E1 state of SERCA is open to the outside.

Answer 17

False. The E1 state of SERCA is open to the inside.

Question 18

Outline the action of the Na++/K+ pump.

Answer 18

1. E1, Na+ ions bound, ATP bound
2. Na+ ions trapped
3. ATP hydrolysis, self phosphorylation
4. Eversion to E2, Na+ ions released
5. Binding of K+
6. K+ ions trapped, release of Pi, ATP rebinding
7. Eversion to E1
8. Release of K+

Question 19

Describe an application of primary active transport.

Answer 19

Digitalis and ouabain both lock the Na+/K+ pump in the E2 conformation.

Question 20

Outline the action of an ABC transporter.

Answer 20

1. Empty transporter
2. Small molecule binds and is trapped; ATP binding site affinity increases
3. 2 ATPs bind causing eversion
4. Small molecule is released
5. ATP hydrolysis and release

Question 21

How is secondary active transport carried out?

Answer 21

After primary active transport creates a gradient, a passive channel or carrier allows ions/molecules to fall back down the gradient with a high value stowaway.

Question 22

Outline the secondary active transport action of lactose permease.

Answer 22

1. Empty carrier, H+ binds and increases affinity for lactose
2. Lactose binds
3. Eversion
4. Lactose released
5. Deprotonation
6. Eversion

Question 23

T or F: By definition, all secondary transporters are antiporters.

Answer 23

False. By definition, all secondary transporters are symporters.

Question 24

List the factors affecting diffusion rates.

Answer 24

1. Magnitude of the concentration gradient
2. Size of the molecule
3. Surface area:volume ratio (shape)
4. Temperature
5. Density of solvent
6. Solubility of solute
7. Distance to destination

Question 25

How will a larger concentration gradient affect diffusion rate?

Answer 25

Faster

Question 26

How will a smaller molecule affect diffusion rate?

Answer 26

Faster

Question 27

How will a higher surface area:volume ratio affect diffusion rate?

Answer 27

Faster

Question 28

How will a lower temperature affect diffusion rate?

Answer 28

Slower

Question 29

How will a solvent with high density affect diffusion rate?

Answer 29

Slower

Question 30

How will a nonpolar solute affect diffusion rate?

Answer 30

Soluble

Question 31

How will a longer distance to the destination affect diffusion rate?

Answer 31

Slower

Question 32

What are 2 important pieces of an ion channel?

Answer 32

1. Selectivity filter | 2. Gate

Question 33

What does movement result from in a bacterial K+ channel?

Answer 33

Results form electrostatic repulsion

Question 34

What are the 3 ways to gate a channel?

Answer 34

1. Voltage 2. Ligand 3. Stress

Question 35

Describe the 5 ion channels that work together to contact the muscles.

Answer 35

1. Depolarization opens voltage-gated Ca++ channels 2. Exocytosed acetylcholine opens ligand-gated Na+ channels 3. Local depolarization opens adjacent voltage-gated Na+ channels 4. As the depolarization spreads, voltage gated Ca++ channels open 5. Coupled Ca++ release channels embedded in SR open

Question 36

What are the various proteins that facilitate diffusion?

Answer 36

Ion channels

Question 37

Describe gap junctions.

Answer 37

Channel, allow cytoplasm sharing, no specificity filter

Question 38

Describe aquaporins.

Answer 38

Channel, let water but not ions through