KA3: membrane proteins: ion transport pumps and generation of ion gradients

Question 1

define the term electrochemical gradient

Answer 1

For a solute carrying a net charge:

concentration gradient and the electrical potential difference combine =>

the electrochemical gradient that determines the transport of the solute

Question 2

what is a membrane potential?

Answer 2

an electrical potential difference

Question 3

when is a membrane potential created?

Answer 3

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

Question 4

give an example of an ion pump

Answer 4

sodium-potassium pump

Question 5

describe the role of ion pumps

Answer 5

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

Question 6

describe the role and function of the sodium-potassium pump

Answer 6

-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

Where is the sodium potassium pump located?

Answer 7

In most animal cells

Question 8

what does the sodium-potassium pump in animals account for?

Answer 8

a high proportion of the basal metabolic rate in many organisms

Question 9

describe the process of the potassium pump

Answer 9

-The pump has high affinity for sodium ions inside the cell; binding occurs

-Phosphorylation by ATP causes theconformation of the protein to change

-Affinity for sodium ions decreases; sodium ions released outside of the cell

-Potassium ions from outside the cell bind to the sodium potassium pump

-Dephosphorylation occurs which causes the conformation of the protein to change

-Potassium ions are taken into the cell and the affinity returns to the start

Question 10

(in the sodium-potassium pump) For each ATP hydrolysed…

Answer 10

3 sodium ions are transported out of the cell

2 potassium ions are transported into the cell.

This establishes both concentration gradients and an electrical gradient

Question 11

in the small intestine, what drives the active transport of glucose?

Answer 11

the sodium gradient created by the sodium-potassium pump

Question 12

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

Answer 12

a sodium ion gradient across the plasma membrane

Question 13

describe the role of the glucose transporter responsible for glucose symport

Answer 13

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

Question 14

describe how the glucose transporter works

Answer 14

-sodium ions enter the cell down their concentration gradient

-the simultaneous transport of glucose pumps glucose into the cell against its concentration gradient.