Absorption Of Products Of Digestion

Question 1

How is the walls of ileum adapted for efficient absorption of the products of digestion?

Answer 1

• ileum walls are folded and have finger like projections called villi increasing the surface area for diffusion to take place
• cell surface membrane do the epithelial cells form finger like projections called microvilli which further increase surface area for absorption
• thin walled, reduces diffusion pathway
• contain muscle which allows them to move which helps maintain concentration gradient for faster diffusion
• well supplied with blood vessels to carry absorbed molecules away which helps to maintain the concentration gradient for faster diffusion

Question 2

How are monosaccharides and amino acids absorbed into the blood?

Answer 2

Glucose and galactose:
1. The sodium-potassium pump actively transports sodium ions out of the epithelial cell into the blood stream and potassium into the cell
2. This creates and maintains a concentration gradient, with a higher concentration of sodium ions in the lumen of the ileum that in the epithelial cell
3. Sodium ions enters the epithelial cell and brings in glucose (or galactose) using a co-transpopter protein via facilitated diffusion
4. This creates and maintains a concentration gradient of glucose (or galactose)
5. Glucose (or galactose) exits the cell by facilitated diffusion via a channel protein and into the bloodstream

Fructose:
• same thing except it is absorbed via facilitated diffusions through a different transporter protein

Amino acids:
• same as glucose and galactose