Unit 1.3(b) - Ion Transport Pumps and Generation of Ion Gradients

Question 1

What is a membrane potential difference (electrical potential difference)?

Answer 1

It is created when there is a difference in electrical charge on the 2 sides of the membrane

Question 2

How does an electrochemical gradient form?

Answer 2

For a solute carrying a net charge, the concentration gradient and membrane potential difference combine to form the electrochemical gradient

Question 3

What is the purpose of pumps?

Answer 3

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

Question 4

What is the job of the Na/K pump?

Answer 4

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

Sodium ions are transported out of the cell and potassium ions into the cell

Question 5

How does the Na/K pump work?

Answer 5

The pump has a high affinity for Na ions inside the cell which bind. The pump is then phosphorylated by ATP and a conformational change occurs decreasing the pumps affinity for Na meaning the ions are released out of the cell. The pump now has a high affinity for K ions which bind.The pump then undergoes dephosphorylation and a conformational change occurs. The K ions are released into the cell and affinity returns to the start

Question 6

How may Na and K ions are transported per ATP hydrolysed?

Answer 6

3 sodium ions are transported out of the cell and 2 potassium ions into the cell. This established both concentration gradients and an electrical gradient

Question 7

Describe glucose symport

Answer 7

In epithelial cells of the small intestine, the Na/K pump generates a Na ion gradient across the plasma membrane, This gradient drives the active transport of glucose via the the glucose symport transporter. Glucose symport involves the co-transport of N into cells (down conc. gradient) and glucose (against its conc. gradient) at the same time in the same direction