Enzymes and digestion
Enzyme action
- Enzymes are proteins that act as biological catalysts - this means they speed up reactions without being used up.
- An enzymeProteins that act as biological catalysts, meaning they speed up reactions without being used up themselves. works on the substrateA substance on which enzymes act., forming products.
- An enzymeâs active siteRegion of an enzyme where the substrate attaches. and its substrate are complementaryShapes that fit together like jigsaw pieces. in shape.
- An enzyme will only work on one substrate - it is substrate specific.
- Enzymes and substrates collide to form enzyme-substrate complexes.
- The substrates are broken down (or in some cases built up).
- The products are released.
- The enzyme is free to act again.
- This theory is known as the âlock and key modelâ.
- It explains why each enzyme will only work on one substrate.
- For example, the active site of amylaseAn enzyme that can break down starch into simple sugars. is only complementary to starch and will therefore only break down starch, not protein or fat.
| Enzyme | Substrate | Product |
| Carbohydrase | Carbohydrate | Simple sugar, glucose |
| Amylase | Starch | Simple sugar, glucose |
| Protease | Protein | Amino acid |
| Lipase | Fat (lipid) | Glycerol and fatty acids |
| Enzyme | Carbohydrase |
|---|---|
| Substrate | Carbohydrate |
| Product | Simple sugar, glucose |
| Enzyme | Amylase |
|---|---|
| Substrate | Starch |
| Product | Simple sugar, glucose |
| Enzyme | Protease |
|---|---|
| Substrate | Protein |
| Product | Amino acid |
| Enzyme | Lipase |
|---|---|
| Substrate | Fat (lipid) |
| Product | Glycerol and fatty acids |
Inhibitors
Inhibitors are molecules that partially fit into an enzymeâs active site but are not broken down.
They inhibit the reaction.
As long as they are in the active site the substrate cannot enter to be broken down, thus reducing the rate of reaction.