Enzymes Flashcards
What are enzymes?
Enzymes are biological catalysts.
How do enzymes work, and how are enzymes specific?
Enzymes have active sites which can only be filled by a specific type of substrate. When correctly filled, they facilitate the reaction but remain unchanged.
How can enzymes become denatured?
With too great a temperature, the bonds in the enzyme are disrupted, leading to a change in shape of the active site which hence no longer fits its intended substrate - becoming denatured.
How do enzymes play a role in the breaking down of carbohydrates, proteins, and lipids in digestion?
- Carbohydrase enzymes break down carbohydrates into sugars, and are present in the mouth (in saliva), the stomach, and the small intestine.
- Protease enzymes break down proteins into amino acids, and are present in the stomach and the small intestine.
- Lipase enzymes break down lipids into fatty acids and glycerol, and are present in the small intestine.
Describe the iodine test for starch.
Add a few drops of iodine on a spatula of the food on a dish. If the iodine turns blue-black, starch is present.
Describe the Benedict’s test for reducing sugars.
- Place two spatulas of the food in a test tube, then add 1ml of water and mix.
- Add 1ml of Benedict’s solution, and mix again.
- Place the test tube in a water bath at about 95°C for a few minutes.
- If the solution turns from blue to cloudy orange or brick red, reducing sugars are present.
Describe the biuret test for proteins.
- Place a spatula of the food in a test tube, then add 1ml of water and mix.
- Add 1ml of potassium hydroxide solution and mix.
- Add 2 drops of copper sulphate solution and stir for 2 minutes.
- If the resultant colour is mauve or purple, proteins are present.
Describe the emulsion test for lipids.
- Place 2 spatulas of the food in a test tube, then add 1ml of water and mix.
- Add 2ml of ethanol, block the top, and shake vigorously.
- A cloudy white emulsion will form if lipids are present.
