1.3b Ion transport pumps and generation of ion gradients

Question 1

What forms the electrochemical gradient that determines the transport of the solute?

Answer 1

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

Question 2

What is the membrane potential?

Answer 2

and electrical potential difference

Question 3

When is a membrane potential created?

Answer 3

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

Question 4

What do ion pumps use energy for and where do they get it from?

Answer 4

• they get it from the hydrolysis of ATP
• to establish and maintain ion gradients

Question 5

Give an example of an ion pump

Answer 5

the sodium-potassium pump

Question 6

What is the function of the sodium-potassium pump?

Answer 6

• It transports ions against a steep concentration gradient using energy directly from ATP hydrolysis.
• It actively transports sodium ions out of the cell and potassium ions into the cell

Question 7

Describe the process of the sodium potassium pump working

Answer 7

1) high affinity for sodium ions inside the cell
2) binding occurs
3) phosphorylation by ATP
4) conformation changes
5) affinity for sodium ions decreases
6) sodium ions released outside the cell
7) potassium ions bind outside the cell
8) dephophorylation
9) conformation changes
10) potassium ions taken into the cell
11) affinity returns to the start

Question 8

What is the proportion of ions for each ATP molecule hydrolysed and what is the purpose of this?

Answer 8

• 3 sodium ions out of the cell
• 2 potassium ions into the cell

-establishes both concentration gradients and an electrical gradient

Question 9

Where is the sodium-potassium pump found and what does it account for?

Answer 9

• it is found in most animal cells
  -accounts for a high proportion of the basal metabolic rate in many organisms

Question 10

What is the function of the sodium potassium pump in the small intestine?

Answer 10

the sodium gradient created by the sodium-potassium pump drives the active transport of glucose

in intestinal epithelial cells the sodium potassium pump generates a sodium ion gradient across the plasma membrane

Question 11

What happens with glucose and sodium in the small intestine?

Answer 11

The glucose transporter transports sodium ions and glucose at the same time and in the same direction.

Question 12

Describe the transport of glucose and sodium in the small intestine

Answer 12

• In intestinal epithelial cells the sodium-potassium pump generates a sodium ion gradient across the plasma membrane
• Sodium ions enter the cell down their concentration gradient; the simultaneous transport if glucose pumps glucose into the cell against its concentration gradient