1p- Ion transport and generation of ion gradients

Question 1

For a solute carrying a net charge what combines to form the electrochemical gradient that determines the transport of the solute?

Answer 1

The concentration gradient and the electrical potential difference

Question 2

When is a membrane potential (an electrical potential difference) created?

Answer 2

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

Question 3

What is an example of an ion pump?

Answer 3

The sodium-potassium pump

Question 4

Where do ion pumps get their energy from, and what do they use it for?

Answer 4

Energy comes from the hydrolysis of ATP, this establishes and maintains ion gradients

Question 5

What does the sodium-potassium pump do?

Answer 5

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

Question 6

What is the step-by-step process of the sodium-potassium pump? (11 steps)

Answer 6

1. the pump has a 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 of the cell
7. potassium ions bind outside of cell
8. dephosphorylation
9. conformation changes
10. potassium ions taken into cell
11. affinity returns to start

Question 7

For each ATP hydrolysed how many sodium and potassiums are transported in and out of the cell, and what does this do?

Answer 7

Three sodium ions out of the cell and two potassium ions into the cell. This establishes both concentration gradients and an electrical gradient

Question 8

Where is the sodium-potassium pump found and why is it important?

Answer 8

It is found in most animal cells and is important because it accounts for a high proportion of the basal metabolic rate in many organisms

Question 9

In the small intestine what does the sodium gradient created by the sodium-potassium pump drive?

Answer 9

The active transport of glucose

Question 10

In intestinal epithelial cells what does the sodium-potassium pump generate?

Answer 10

A sodium ion gradient across the plasma membrane

Question 11

What does the glucose transporter responsible for the sodium potassium pump in the small intestine do?

Answer 11

Transports sodium ions and glucose at the same time and in the same direction

Question 12

How does the active transport of glucose in the small intestine come about?

Answer 12

Sodium ions enter the cell down their concentration gradient, the simultaneous transport of glucose pumps glucose into the cell against its concentration gradient