Co-transport And Absorption of Glucose In The Ileum

Question 1

What do the microvilli provide

Answer 1

More surface area for the insertion of carrier proteins through which diffusion, facilitated diffusion and active transport can take place

Question 2

What’s a mechanism that can increase transport across membranes?

Answer 2

to increase the number of protein channels and carrier proteins in a given area of membrane

Question 3

What’s the role of diffusion in absorption

Answer 3

As carbohydrates and proteins are being digested continuously, there is normally a greater concentration of glucose and amino acids within the ileum than in the blood therefore a concentration gradient down which glucose moves by facilitated diffusion from inside the ileum into the blood.

Question 4

How is the concentration gradient between the ileum and the blood maintained for diffusion

Answer 4

As blood is constantly being circulated by the heart, the glucose absorbed into it is continuously being removed by the cells as they use it up during respiration.

This means rate of movement by facilitated diffusion across epithelial cell surface membranes is increased

Question 5

Describe co transport of glucose molecules

Answer 5

1. Sodium ions are actively transported out of epithelial cells, by the sodium potassium pump, into the blood. This takes place I. One type of protein - Carrier molecule found in the cell surface membrane of epithelial cells
2. This maintains a much higher concentration of sodium ions in the lumen of the intestine that inside the epithelial cells
3. Sodium ions diffuse into the epithelial cells down this concentration gradient through a different type of proteins carrier ( co transport protein) in the cell surface membrane. As the sodium ions diffuse in through this second carrier protein, they carry either amino acid molecules or glucose molecules into the cells with them
4. The glucose/amino acids pass into the blood plasma by facilitated diffusion using another type of Carrier

Question 6

Why’s it an indirect rather then direct form of active transport

Answer 6

Both sodium ions and glucose/amino acid molecules move into the cell, but while the sodium ions move down their concentration gradient, the glucose molecules move against their gradient. It is the sodium ion concentration gradient, rather then ATP directly that powers the movement of glucose and amino acids into the cells