Comprehension - L05-L06

Question 1

What is a facilitative transporter?

Answer 1

Binding of the solute triggers a conformational change in the transmembrane protein that exposes the solute to the other side

Question 2

What is an example of a facilitative transporter?

Answer 2

GLUT4
Continued diffusion of glucose in the cell is possible because it’s phosphorylated

Question 3

What are 5 examples of passive transport mechanisms?

Answer 3

1. Diffusion through membrane
2. Voltage gated ion channel
3. Facilitative transporter
4. Osmosis
5. Ligand gated channel

Question 4

What type of energy is used in active transport?

Answer 4

Hydrolysis of ATP (Primary active transport)
Flow of other substances down their concentration gradients (secondary active transport

Question 5

What are the 3 types of primary active transport?

Answer 5

1. P-type pump
2. V-type pump
3. ABC transport

Question 6

How does the P-type pump work?

Answer 6

• Becomes phosphorylated during active transport
  -Contributes to maintaining the membrane potential voltage in cells

Question 7

What is pumped in/out per one ATP in the Na/K-ATPase P-type ion pump?

Answer 7

3 Na+ pumped out and 2 K+ pumped in

Question 8

What are the steps of the Na+/K+ -ATPase P-Type ion pump?

Answer 8

1. High affinity for Na+ and ATP is bound
2. Protein closes once ions are bound
3. Hydrolysis of ATP and pump is phosphorylated
4. Release of ADP –> E2. Loses affinity for Na+, high affinity for K+
   5-7. Dephosphorylation
   7-8. ATP binds,–>E1. Low affinity for K+

Question 9

What are the characteristics of V-type ion pumps?

Answer 9

Use ATP but don’t become phosphorylated
Transport H ions across organelles and vacuoles
Also found in PM of some cells

Question 10

What are the characteristics of an ABC transporter?

Answer 10

-ATP Binding Cassette transporters
- Share similar structure of ATP binding domain
- Transport ions, lipids, peptides, and nucleosides

Question 11

In secondary active transport, what is a symporter?

Answer 11

• Transports two substances in the same direction
• Also called cotransporter

Question 12

In secondary active transport, what is an anti porter?

Answer 12

• Transports two substances in opposite directions
• Also called an exchanger

Question 13

What does the Na+/glucose cotransporter do?

Answer 13

• Transport glucose from the lumen into epithelial cells
• Na+ ions [ ] is low inside cells
• Na+ ions moving down their [ ] gradient is used to drive the cotransport of glucose

Question 14

What form of transport establishes the Na+ [ ] gradient in the first place?

Answer 14

Primary active P- Type

Question 15

What is FRAP?

Answer 15

Fluorescence recovery after photobleaching
- Technique to study movement of membrane components

Question 16

What are the 3 steps of FRAP?

Answer 16

1. Label membrane w fluorescent dye
2. Photobleach from a portion of cell
3. Monitor reappearance of fluorescence in the previously bleached portion.

Question 17

What does the rate of recovery of fluorescence measure in FRAP?

Answer 17

Rate of diffusion of the fluorescently labeled portion

Question 18

When isolating membrane proteins, what is the first step? What happens in this step?

Answer 18

Lyse the cells!
Mechanical disruption (Hypotonic)
Pellet 1: insoluble membranes and proteins
Supernatant 1: soluble material

Question 19

When isolating membrane proteins what is the second step? What happens in this step?

Answer 19

Isolate peripheral proteins!
High salt solution
Pellet 2: transmembrane proteins
Supernatant 2: Peripheral proteins

Question 20

When isolating membrane proteins, what is the third step? What happens in this step?

Answer 20

Isolate Transmembrane proteins!
Strong detergent to break VDW interactions
Pellet 3: GPI-anchored proteins
Supernatant 3: Transmembrane protein

Question 21

Where are GPI-anchored proteins usually found?

Answer 21

In detergent resistant portions of the membranes that are rich in cholesterol and sphingolipids

Question 22

When isolating membrane proteins, what is the fourth step? What happens in this step?

Answer 22

Isolate GPI-anchored protein
Treatment w PI-PLC
Pellet 4: insoluble materials
Supernatant 4: GPI-anchored proteins

Question 23

When performing SDS-Page, how are proteins separated by size?

Answer 23

Adding SDS to the samples. This is a negatively charged amphipathic detergent that gives proteins a uniformly negative charge and denatures the protein

Question 24

What is the name of the dye that stains the proteins in polyacrylamide gel electrophoresis?

Answer 24

coomassie blue