Digestion and Absorption

Question 1

Digestion

Answer 1

Hydrolysis of large insoluble molecules into smaller molecules which can be absorbed across cell membranes

Question 2

Digestion of Carbohydrates

Answer 2

Mouth:
Amylase hydrolyses starch

Small Intestine:
Maltase hydrolyses maltose into glucose
Sucrase hydrolyses sucrose into glucose and fructose
Lactase hydrolyses lactose into glucose and galactose
Pancreatic amylase

Question 3

Digestion of Proteins

Answer 3

Endopeptidases hydrolyse the peptide bonds of amino acids in the centre of a polypeptide chain

Exopeptidases hydrolyses the peptide bonds between amino acids at the end of the polypeptide chain

Dipeptidases hydrolyse dipeptides into single amino acids.

Question 4

Absorption of Amino Acids and Glucose

Answer 4

Amino acids and glucose are absorbed into the ileum via co transport with sodium ions.

The sodium potassium pump causes sodium ions to move from the intestinal epithelial cells into the blood causing the sodium ions in the lumen of the ileum to diffuse into the epithelial cells down a concentration gradient and the amino acids and glucose are co-transported with them. The glucose and amino acids are then absorbed into the blood via facilitated diffusion

Question 5

Digestion of Lipids

Answer 5

Small Intestine
Bile salts emulsifies lipids into tiny droplets called micelles, increasing their surface area.
Pancreatic lipase hydrolyses triglycerides into monoglycerides and fatty acids

Question 6

Absorption of Lipids

Answer 6

The fatty acids and monosaccharides are absorbed by the intestinal epithelium cells inside the intestinal cell wall.
They are then resynthesised into triglycerides and packaged into vesicles called chylomicrons.
The chylomicrons are released via exocytosis into a lacteal, a lymphatic vessel which filters into the blood stream.