Biology · IGCSE · Cambridge · Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) · Specification point · 7.4 · Human nutrition
7.4 Chemical digestion
| Core | Supplement |
|---|---|
1 Describe chemical digestion as the breakdown of large insoluble molecules into small soluble molecules | |
2 State the role of chemical digestion in producing small soluble molecules that can be absorbed | |
3 Describe the functions of enzymes as follows: (a) amylase breaks down starch to simple reducing sugars (b) proteases break down protein to amino acids (c) lipase breaks down fats and oils to fatty acids and glycerol | |
4 State where, in the digestive system, amylase, protease and lipase are secreted and where they act | |
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5 Describe the functions of hydrochloric acid in gastric juice, limited to killing harmful microorganisms in food and providing an acidic pH for optimum enzyme activity
6 Describe the digestion of starch in the digestive system: (a) amylase breaks down starch to maltose (b) maltase breaks down maltose to glucose on the membranes of the epithelium lining the small intestine |
7 Describe the digestion of protein by proteases in the digestive system: (a) pepsin breaks down protein in the acidic conditions of the stomach (b) trypsin breaks down protein in the alkaline conditions of the small intestine |
8 Explain that bile is an alkaline mixture that neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action |