4.5: Co-Transport and absorption of glucose in the Ileum

Question 1

How is the rate of movement across membranes increased

Answer 1

1. Presence of Microvilli

2. Increased density of protein channels and carrier proteins

Question 2

How do microvilli increase the rate of movement across membranes

Answer 2

They are finger-like projections of the cell membrane and provide more surface area for the insertion of carrier proteins

Question 3

What are constantly digested

Answer 3

Carbohydrates and proteins

Question 4

What does the constant digestion of carbohydrates and proteins mean

Answer 4

That there is normally a greater concentration of glucose and amino acids within the ileum than in the blood

Question 5

What does a higher concentration of glucose and amino acids in the ileum than in the blood mean

Answer 5

That there is a concentration gradient down which glucose moves by facilitated diffusion from the inside of the ileum to the blood

Question 6

What does diffusion only result in

Answer 6

The concentrations either side of the inestinal epithelial becoming equal. Therefore not all glucose/amino acids are abosrbed

Question 7

Why are most of the glucose/amino acids actually absorbed

Answer 7

Because glucose and amino acids are actively transported - therefore they are both all absorbed into the blood

Question 8

What is the mechanism by which glucose and amino acids are absorbed from the small intestine

Answer 8

Co-Transport

Question 9

How are glucose and amino acids absorbed via co-transport

Answer 9

Glucose and amino acids are drawn into the cells along with sodium ions that have been actively transported out by the Na/K pump.

Question 10

Process of co-transport

Answer 10

1. Sodium ions are actively transported out of epithelial cells, by the na/k pump and into the blood
2. This maintains a much higher concentration of sodium ions in the lumen of the intestine than the inside of epithelial cells
3. Sodium ions diffuse into the epithelial cells down this conc gradient through a co-transport protein in the membrane. As sodium ions diffuse down they carry either amino acids or glucose molecules into the cell with them
4. The glucose/amino acids pass into the blood plasma by facilitated diffusion.

Question 11

Where is ATP used

Answer 11

in the production of a Na concentration gradient (Sodium/Pottasium pump)