3.3.2 Enzymes in Digestion

Carbohydrate Digestion:

1. Amylase:

• Produced in the salivary glands and pancreas.
• Hydrolyses starch into maltose by breaking glycosidic bonds.

2. Maltase:

• Found in the ileum (small intestine).
• Hydrolyses maltose into two glucose molecules.

3. Other Disaccharidases:

• Sucrase:
• Hydrolyses sucrose into glucose and fructose.
• Lactase:
• Hydrolyses lactose into glucose and galactose.

Lipid Digestion:

4. Lipase:

• Secreted by the pancreas, acts in the small intestine.
• Hydrolyses the ester bond in triglycerides, producing monoglycerides and fatty acids.

5. Bile Salts (from the liver):

• Emulsify lipids into smaller droplets (micelles), increasing surface area for lipase action.

Protein Digestion:

6. Peptidases (also called proteases):

• Hydrolyse peptide bonds in proteins to produce amino acids.
• Types of peptidases:
• Endopeptidases:
• Act on internal peptide bonds, breaking the protein into smaller polypeptides.
• Examples: Pepsin (stomach) and trypsin (pancreas).
• Exopeptidases:
• Act on terminal peptide bonds, releasing single amino acids.
• Found in the small intestine.
• Dipeptidases:
• Act on dipeptides, hydrolysing them into individual amino acids.
• Located on the epithelial cells of the ileum.

Enzyme Locations:

Molecule	Enzyme	Location	Product
Carbohydrates	Amylase	Mouth, pancreas	Maltose
	Maltase, sucrase, lactase	Ileum	Monosaccharides (glucose, fructose, galactose)
Lipids	Lipase	Pancreas, small intestine	Monoglycerides and fatty acids
Proteins	Endopeptidases	Stomach, pancreas	Polypeptides
	Exopeptidases	Small intestine	Amino acids
	Dipeptidases	Ileum (epithelial cells)	Amino acids

Key Processes:

1. Hydrolysis:

• The breaking of chemical bonds (e.g., glycosidic, ester, peptide) by the addition of water, catalysed by enzymes.

2. Emulsification:

• Breakdown of large lipid droplets into smaller ones by bile salts, increasing surface area for lipase action.

Key Terms:

• Glycosidic Bond: Bond between sugar molecules in carbohydrates.
• Ester Bond: Bond between glycerol and fatty acids in lipids.
• Peptide Bond: Bond between amino acids in proteins.