4.5 Co-transport and absorption of glucose in the ileum

Question 1

What component do epithelial cells lining the ileum possess

Answer 1

Microvilli

Question 2

What are microvilli

Answer 2

Finger-like projections of the cell-surface membrane

Question 3

What is the function of microvilli

Answer 3

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

Question 4

What is the process of co-transport in the small intestine

Answer 4

1. Sodium ions are actively transported out of epithelial cells, by the sodium-potassium pump, into the blood. This takes place in 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 than inside the epithelial cells
3. Sodium ions diffuse into the epithelial cells down this concentration gradient through a different type of protein 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 cell with them
4. The glucose/amino acids pass into the blood plasma by facilitated diffusion using another type of carrier

Question 5

Why is the term ‘co-transport’ used to describe the transport of glucose into cells

Answer 5

Because glucose molecules and sodium ions move into the cells coupled together