Enzymes in Digestion (Cambridge O Level Biology)

Amylases

• Amylases are enzymes that are produced in the mouth and the pancreas (secreted into the duodenum)
• Amylases digest starch into smaller sugars

Enzyme Digestion of Starch into Glucose Diagram

The digestion of starch

• Amylase is secreted into the alimentary canal in the mouth and the duodenum (from the pancreas) and digests starch to maltose (a disaccharide)
• Maltose is digested by the enzyme maltase into glucose on the membranes of the epithelium lining of the small intestine

Proteases

• Proteases are a group of enzymes that break down proteins into amino acids in the stomach and small intestine (with the enzymes in the small intestine having been produced in the pancreas)

Action of Proteases in Digestion Diagram

The digestion of proteins

• Protein digestion takes place in the stomach and duodenum with two main enzymes produced
  • Pepsin is produced in the stomach and breaks down protein in acidic conditions
  • Trypsin is produced in the pancreas and secreted into the duodenum where it breaks down protein in alkaline conditions
  • Both pepsin and trypsin have an optimum pH that they work best in
    • Working in combination, both enzymes ensure as much protein as possible is digested chemically before its amino acids are absorbed in the ileum

Lipases

• Lipase enzymes are produced in the pancreas and secreted into the duodenum
• They digest lipids into fatty acids and glycerol

Lipid Digestion Diagram

The digestion of lipids