Carbohydrates application

Question 1

Following digestion and absorption of food, the undigested remains are processed to form faeces in the parts of the intestine below the ileum.

The faeces of people with constipation are dry and hard. Constipation can be treated by drinking lactulose. Lactulose is soluble, but is not digested or absorbed in the human intestine.

Use your knowledge of water potential to suggest why lactulose can be used to help people suffering from constipation.

Answer 1

(Lactulose) lowers the water potential of faeces / intestine / contents of the intestine;

2. Water enters (due to osmosis) and softens the faeces;

Question 2

Explain how digestion of starch in the gut (small intestine) leads to an increase in the concentration of glucose in the blood. Details of co-transport are not required.

Answer 2

Hydrolysed by enzymes / hydrolysed by amylase / maltase;

If named enzyme given, it must relate to the correct substrate

2. Produces glucose (in the gut);
3. Small enough to cross the gut wall (into the blood) / monomers / monosaccharides (can) cross the gut wall (into the blood);

Accept cell membranes / epithelium / cells for ‘gut wall’

Question 3

The formula for galactose is C6H12O6. What is the formula for lactose?

Answer 3

C12 ; H22O11 ;