4.5 Co-transport and absorption of glucose in the ileum

Question 1

How is the rate of movement across the membrane increased?

Answer 1

• micro villi provide more surface area for carrier proteins which allow diffusion, facilitated diffusion and active transport to occur.
• increase the number of protein channels and carrier proteins on the membrane

Question 2

What is the role of diffusion in absorption of products in the ileum?

Answer 2

• there is a higher conc. of glucose and amino acids in the ileum than the blood as carbohydrates and proteins are constantly being digested.
• this means they diffuse into the blood
• blood is constantly being circulated so there is a constantly glucose being removed by cells as they use it for respiration.
• this helps to maintain the concentration gradient and means the rate of movement by facilitated diffusion is increased

Question 3

What is the role of active transport in the absorption of products in the ileum?

Answer 3

• Diffusion only gets max. half of the prducts abrobed, until it reaches equilibrium, so some amino acids and glucose may pass out of the body.
• this does not happen because they are also absorbed by active transport.
• this means all glucose and amino acids can be absorbed
• the mechanism is called co-transport

Question 4

What is co-transport in reference to the ileum?

Answer 4

Glucose and amino acids are drawn into the cells along with sodium ions which have been actively transported out by the sodium-potassium pump.

Question 5

Describe the process of co-transport in the ileum.

Answer 5

1) sodium ions are actively transported out of epithelial cells by the sodium potassium pump into the blood. this takes place in a protein-carrier molecule in the cell-surface membrane
2) this maintains a higher concentration of sodium ions in the lumen than inside epithelial cells
3) sodium ions diffuse into the epithelial cells down a carrier protein (co-transport protein). as sodium ions diffuse in, they carry either amino acids or glucose into the cell with them
4) the glucose/amino acids move into the blood plasma by facilitated diffusion.
ATP powers the movement of glucose/amino acids as they move against their concentration gradient.