3.10 - Digestive Enzymes
The three groups of digestive enzymes
- Digestive enzymes are biological catalysts - they speed up the breakdown of food without being used up themselves.
- Starch, proteins, and fats are big molecules that are too large, and mostly insoluble, so they can't pass through the wall of the digestive system into the blood.
- Digestive enzymes break these big molecules into much smaller, soluble ones, which can pass easily through the gut wall, be absorbed into the bloodstream, and be carried to the body's cells.
- Different enzymes break down different types of food, and there are three main groups.
The three enzyme groups and what they do
| Enzyme group | Breaks down | Into |
|---|---|---|
| Carbohydrases | Carbohydrates | Simple sugars |
| Proteases | Proteins | Amino acids |
| Lipases | Lipids (fats and oils) | Glycerol and fatty acids |
The carbohydrase example to know is amylase, which breaks down starch (a carbohydrate made of a long chain of glucose units) into sugars.
What the small molecules are used for
- The small molecules released by digestion are not waste.
- Once absorbed, the body uses them to build new carbohydrates, proteins, and lipids that it needs.
- Some of the glucose from digested starch is used in respiration to release energy.
TermDefinition
CarbohydraseAn enzyme that breaks down carbohydrates into simple sugars.
AmylaseA carbohydrase enzyme that breaks down starch into sugars.
ProteaseAn enzyme that breaks down proteins into amino acids.
LipaseAn enzyme that breaks down lipids into glycerol and fatty acids.
Key points to remember
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