Digestion and Absorption

Question 1

Complete breakdown of starch (4)

Answer 1

1. Salivary/pancreatic amylase hydrolyses starch into maltose
2. By hydrolysing glycosidic bonds
3. Maltose hydrolysed into glucose
4. By maltase

Question 2

Describe how glucose is absorbed from the ilium into the blood (5)

Answer 2

1. Sodium ions actively transported out of epithelial cell into the blood by sodium potassium pump
2. This creates a concentration gradient of sodium ions
3. Sodium ions and glucose enter by facilitated diffusion using cotransporter proteins
4. Sodium ions diffuse into the cell down their concentration gradient
5. Glucose moves into the cell against its concentration gradient
6. Glucose moves into the blood by facilitated diffusion

Question 3

What do endopeptidases do?

Answer 3

Hydrolyse peptide bonds within the polypeptide chain

Question 4

What do exopeptidases do?

Answer 4

Hydrolyse the peptide bonds at the terminal ends of the protein

Question 5

What do dipeptidases do?

Answer 5

Hydrolyse dipeptides into amino acids

Question 6

Lipid digestion and absorption process

Answer 6

1. Lipid droplets mixed with bile salts to form smaller droplets
2. Smaller droplets increase the surface area for faster hydrolysis by lipase
3. Triglycerides hydrolysed into glycerol, fatty acids, and monoglycerides
4. Bile salts, glycerol, and fatty acids form micelles
5. Micelles make fatty acids soluble in water and bring fatty acids to the surface of the epithelial cell membrane
6. Fatty acids enter epithelial cell by simple diffusion
7. At the smooth endoplasmic reticulum: fatty acids and glycerol are recombined to form triglycerids
8. At the golgi body: triglycerides are modified, and proteins are added to form lipoprotein called chylomicrons and packaged into vesicles
9. Chylomicrons are transported into a lymph vessel by exocytosis. They then enter the blood