Digestion and absorption of carbohydrates

Question 1

Where are carbohydrates broken down

Answer 1

Mouth and stomach

Question 2

Where are enzymes produced for breaking down starch (carbohydrates)

Answer 2

Salivary gland, pancreas and small intestine

Question 3

Salivary gland

Answer 3

Produces amylase that hydrolyses the glycosidic bonds in starch into maltose

Question 4

Pancreas

Answer 4

Produces pancreatic amylase that also hydrolyses glycosidic bonds in starch to produce maltose

Question 5

Why does the pancreas also contain amylase

Answer 5

Digesting all the starch in the mouth with amylase would take too long so it is also digested in the pancreas as well

Question 6

Small intestine (ileum)

Answer 6

Contains 3 membrane bound disaccharidases (Maltase, sucrase and lactase)
Hydrolyses respective disaccharides into monosaccharides
e,g Maltase hydrolyses maltose into glucose etc.

Question 7

How does glucose and galactose move into the epithelial cells

Answer 7

Co-transport with sodium ions into the epithelial cell and then facilitated diffusion into the capillaries

Question 8

How does fructose move into the epithelial cells

Answer 8

Facilitated diffusion into capillary by a different transport protein

Question 9

Process of glucose moving from Ileum lumen into capillaries

Answer 9

1) Glucose moves into epithelial cells by facilitated diffusion until equilibrium
2) After equilibrium, glucose is co-transported with sodium ions into the epithelial cell and the energy is given mainly by the concentration difference of sodium ions
3) After entering the epithelial cells the glucose molecules diffuse into the capillaries by facilitated diffusion

Question 10

Role of Sodium/potassium pump

Answer 10

The sodium potassium pump is in the epithelial cell and constantly pumps sodium ions into the capillaries out of the epithelial cells to give the epithelial cell a low concentration of sodium ions. This is because sodium ions need to co-transport glucose and amino acids into the epithelial cell. The pump requires ATP

Question 11

Adaption of ileum for absorption

Answer 11

Long - Large SA
Folded - Large SA
Villi - Large SA
Thin epithelium (inner layer - Short diffusion pathway one cell thick
Micro villi - Large SA
Mitochondria - ATP for active transport of sodium ions and ATP for Na/K pump
Good blood supply - Maintain concentration gradient