Unit 1 Part 3b (Ion Transport Pumps)

Question 1

Describe the electrochemical gradient

Answer 1

For a solute carrying a net charge, the concentration gradient and the electrical potential difference combine to form the electrochemical gradient that determines the transport of the solute

Question 2

What is membrane potential?

Answer 2

Is created when there is a difference in electrical charge on the two sides of the membrane

Question 3

What do ion pumps do?

Answer 3

Use energy from the hydrolysis of ATP to establish and maintain ion gradients

Question 4

What does the sodium-potassium pump do?

Answer 4

Transports ions against a steep concentration gradient using energy directly from ATP hydrolysis

Question 5

Describe the action of the sodium potassium pump?

Answer 5

1. Pump has high affinity for Na inside cell
2. Binding occurs, phosphorylation by ATP, conformation changes
3. Affinity for Na decreases and Na is released outside of the cell
4. k ions bind to outside of cell
5. Dephosphorylation, conformation change and K ions enter the cell
6. Affinity returns to start

For each ATP hydrolysed, 3 Na are transported out of the cell and 2 K transported into the cell.

Question 6

What does the sodium potassium pump account for a high proportion of?

Answer 6

Basal metabolic rate in many organisms

Question 7

Describe the sodium potassium pump in the small intestine?

Answer 7

The sodium gradient created by the pump drives the active transport of glucose in epithelial cells

Question 8

Describe the action of the glucose symport

Answer 8

Transports sodium down its concentration gradient and simultaneously transports glucose against its concentration gradient