3.3 Digestion and absorption

Question 1

Amylase

Answer 1

Catalysing hydrolysis reactions that break glycosidic bonds in starch to produce maltose. Produced by the salivary glands and the pancreas

Question 2

Membrane-bound disaccharidases

Answer 2

Enzymes that are attached to the cell membranes of epithelial cells lining the ileum. Break down disaccharides to monosaccharides

Question 3

Lipase enzymes

Answer 3

catalyse breakdown of lipids into monoglycerides and fatty acids by hydrolysing ester bonds. Lipase made in pancreas and secreted into small intestine

Question 4

Bile salts

Answer 4

Produced by the liver and emulsify lipids. Lipids form several small droplets with a higher surface area for lipase to act on

Question 5

Endopeptidases

Answer 5

Hydrolyse peptide bonds within a protein

Question 6

Exopeptidases

Answer 6

Hydrolyse peptide bonds at the ends of protein molecules, removing single amino acids

Question 7

Dipeptidases

Answer 7

Hydrolyse the peptide bonds in a dipeptide. Usually located in the cell-surface membrane of epithelial cells in small intestine

Question 8

Monosaccharides

Answer 8

Glucose and galactose absorbed by active transport with sodium ions via a co-transporter. Fructose absorbed via facilitated diffusion

Question 9

Monoglycerides and fatty acids

Answer 9

Micelles help move monoglycerides and fatty acids towards epithelium. Micelles release them, so monoglycerides and fatty acids are absorbed. They are lipid soluble so they can diffuse directly across cell membrane. Micelles are not taken up across epithelium

Question 10

Micelles

Answer 10

Monoglycerides and fatty acids stick with bile salts to form micelles, help products of lipid digestion to be absorbed

Question 11

Amino acids

Answer 11

Sodium ions actively transported out of epithelial cells into ileum. Sodium can diffuse through sodium-dependent transporter proteins in cell membrane, carrying amino acids with them