Exchange Across Cell Membranes - Active Transport

Question 1

What is active transport?

Answer 1

Active transport uses energy to move molecules and ions across membranes, against their conc gradient

Question 2

What proteins are involved in active transport?

Answer 2

Carrier proteins - a molecule attaches to the protein, the protein changes shape and releases the molecule on the other side of the membrane

Question 3

What are the two main differences between active transport and facilitated diffusion?

Answer 3

1. Active transport moves substances from a low to high conc - facilitated diffusion moves substances from a high to low conc
2. Active transport require energy - facilitated diffusion does not

Question 4

Give a type of carrier protein

Answer 4

Co-transporters

Question 5

How do co-transporters work?

Answer 5

They bind to two molecules at a time. The conc gradient of one molecule is used to move the other molecule against its own conc gradient

Question 6

Give three things that affect the rate of active transport

Answer 6

1. The speed of the individual carrier proteins
2. The number of carrier proteins present
3. The rate of respiration and availability of ATP

Question 7

How does the speed of the carrier proteins affect the rate of active transport?

Answer 7

The faster they work, the faster the rate of active transport

Question 8

How does the number of carrier proteins affect the rate of active transport?

Answer 8

The more proteins there are, the faster the rate of active transport

Question 9

How does the rate of respiration affect the rate of active transport?

Answer 9

If respiration is inhibited, active transport can’t take place

Question 10

Where is glucose absorbed into the bloodstream?

Answer 10

Small intestine - glucose is absorbed from the lumen (middle) of the ileum by co-transport

Question 11

Explain co-transport of glucose

Answer 11

1. Na+ ion are actively transported out of the ileum epithelial cells, into the blood, by a Na/K pump. This creates a conc gradient - now a higher conc of Na ions in lumen of the ileum than in the cell
2. Na ions diffuse from the lumen of the ileum into the epithelial cell, down their conc grad. They do this via sodium-glucose co-transporter proteins
3. The co-transporter carries glucose into the cell with the Na - conc of glucose inside the cell increases
4. Glucose diffuses out the cell, into the blood, down its conc grad through a channel protein via facilitated diffusion