Programme 21: Food and Digestion

Activity Sheet 3

Enzyme True or False

• Decide whether each statement is true or false.
• Then decide if the second statement explains the first.

1A

Bile digests fats.
B

Bile does not contain enzymes.

2A

Enzymes are sensitive to temperature.
B

The shape of an enzyme molecule can be permanently altered by high temperature.

3A

The optimum pH for all enzymes is pH 7.
B

Pepsin works best in acid conditions.

4A

Enzymes only work with one substrate.
B

Enzymes are produced by a particular gland in the digestive system.

5A

An enzyme molecule can help to digest many molecules of its particular substrate.
B

Enzymes are biological catalysts.

6A

In the stomach proteins are mainly digested by acids.
B

Hydrochloric acid is secreted in the stomach where protein is digested.

7A

Enzymes are denatured by cold temperature.
B

Enzymes work more slowly at low temperatures.

8A

All nutrients have to be digested before they can be absorbed into the blood.
B

Large molecules cannot pass through the wall of the small intestine.

9A

Pink phenolphthalein indicator is decolourised when fat is digested by lipase.
B

Fatty acids are made when fats are digested by lipase.

10A

Amylase digests starch to make glucose, a simple sugar.
B

Starch is a complex carbohydrate made up of many thousands of glucose molecules.