Digesting starch and protein in detailSpec 7.4.6, 7.4.7
Starch
- Amylase from the salivary glands and the pancreas breaks starch down to maltose.
- Maltase breaks maltose down to glucose. Maltase is on the membranes of the epithelium lining the small intestine.
- Glucose is small and soluble, so it can be absorbed into the blood.
Protein
| Protease | Where it works | Conditions |
|---|---|---|
| Pepsin | Stomach | Acidic, because of the hydrochloric acid in gastric juice |
| Trypsin | Small intestine | Alkaline, because of the bile mixed with the food |
Each enzyme has an optimum pH. Pepsin works best in acid and trypsin works best in alkali. Both are proteases, so both break down protein.
(opens full size in a new tab)Amylase does not make glucose directly. It makes maltose, and maltase then makes glucose. Link each enzyme to its own product.
Quick check
What is chemical digestion?
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The breakdown of large insoluble molecules into small soluble molecules.
What does lipase break down fats and oils into?
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Fatty acids and glycerol.
Where is amylase secreted?
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Salivary glands and pancreas.
Supplement Which enzyme breaks maltose down to glucose, and where is it found?
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Maltase, on the membranes of the epithelium lining the small intestine.
Supplement Why does trypsin work in the small intestine but pepsin does not?
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Trypsin works in alkaline conditions and pepsin works in acidic conditions; bile makes the small intestine alkaline.