2B - Exchange across cell membranes (active transport)

Question 1

What is active transport?

Answer 1

The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.

Question 2

What does active transport use?

Answer 2

Highly specific carrier proteins and ATP.

Question 3

Is active transport active or passive?

Answer 3

Active.

Question 4

Does active transport occur with or against the concentration gradient?

Answer 4

Against.

Question 5

How does active transport happen?

Answer 5

A molecule attaches to the carrier protein, the protein changes shape and this moves the molecule across the membrane, releasing it on the other side.

Question 6

What are the differences between active transport and facilitated diffusion?

Answer 6

Active transport usually moves solutes from a low to high concentration - in facilitated diffusion, they always move from high to low concentration.

Active transport requires energy - facilitated diffusion does not.

Question 7

What source of energy is used in active transport?

Answer 7

ATP produced in respiration.

Question 8

How is energy released so that solutes can be transported by active transport?

Answer 8

ATP undergoes a hydrolysis reaction, splitting into ADP and Pi releasing energy.

Question 9

What type of protein does active transport use?

Answer 9

Carrier proteins.

Question 10

What is an example of how active transport is used in the body?

Answer 10

The sodium/potassium pump found in all animal cell membranes. It continually uses ATP to actively pump sodium out of the cell and potassium into the cell creating concentration gradients across the membrane.

Question 11

What are co-transporters?

Answer 11

A type of carrier protein.

Question 12

What is co-transport?

Answer 12

When one molecule is moved by facilitated diffusion with the concentration gradient and at the same time one molecule is moved against the concentration gradient by active transport using the same carrier protein.

Question 13

What is it called when substances are moved in the same direction in co-transport?

Answer 13

Symport.

Question 14

What is it called when substances are moved in opposite direction in co-transport?

Answer 14

Antiport.

Question 15

What factors affect the rate of active transport?

Answer 15

The speed of individual carrier proteins - the faster they work, the faster the rate of active transport.

The number of carrier proteins present - the more proteins there are, the faster the rate of active transport.

The rate of respiration in the cell and the availability of ATP - if respiration is inhibited, active transport can’t take place.

Question 16

What is an example of where co-transport is used in the body?

Answer 16

In the cavity (lumen) of ileum.

Glucose is absorbed into the bloodstream in the small intestine.
The concentration of glucose in the ileum is too low for glucose to diffuse out into the blood so it is absorbed from the lumen of the ileum by co-transport.

Question 17

Explain how glucose enters the ileum epithelium with sodium ions using co-transport.

Answer 17

Sodium ions are actively transported out of the ileum cells into the blood by the sodium-potassium pump creating a concentration gradient. (Higher concentration of sodium ions in the lumen of the ileum than inside the cell).

This causes sodium ions to diffuse from the lumen into the epithelial cell down the conc. gradient. This happens via the sodium-glucose co-transporter proteins.

The co-transporter carries glucose into the cell with the sodium and as a result, the conc. of glucose inside the cell increases.

Glucose diffuses out of the cell, into the blood, down its conc. gradient through a protein channel by facilitated diffusion.

Question 18

What 2 processes occur in co-transport?

Answer 18

Facilitated diffusion and active transport.