4.5 Co-transport and absorption of glucose in the ileum

Question 1

What is co-transport?

Answer 1

The transport of one substance coupled with the transport of another substance across a plasma membrane in the same direction through the same protein carrier.

Question 2

How may cells be adapted for rapid transport across their internal or external membranes?

Answer 2

1. increase the surface area
2. increase the number of protein channels and carrier protein

Question 3

What are the examples of adaptations of epithelial cells to increase the rate of transport across their internal and external membranes?

Answer 3

1. the epithelial cells that are lining the ileum (small intestine) have microvilli
   ↳ they provide more surface area for the insertion of carrier proteins through, which diffusion, facilitated diffusion and active transport can take place
2. maintaining concentration gradient of glucose between the inside of ileum and the blood
   ↳ glucose is continuously absorbed from the lumen of the small intestine into the bloodstream and then removed by cells during respiration
3. co-transport
   ↳ glucose or amino acids are drawn into cells along with sodium ions that have been actively transported out by the sodium-potassium pump

Question 4

How does co-transport of glucose molecules work?

Answer 4

1. sodium ions are actively transported out the epithelial cell
2. this maintains a much higher concentration of sodium ions in the lumen of the intestine
3. sodium ions diffuse into the epithelial cells down this concentration gradient through a different type of protein carrier
4. as sodium ions diffuse in, they carry either amino acids or glucose into the cell with them
5. glucose/amino acids pass into the blood plasma through facilitated diffusion

Question 5

Do sodium ions move down or against the concentration gradient when moving into the cell?

Answer 5

Down

Question 6

Does glucose move down or against the concentration gradient when moving into the cell?

Answer 6

Against