Question

(a) Different digestive enzymes work best at different pH values. The best pH for enzyme activity is called its optimum pH.

Fig. 4.1 shows the optimum pH of five different digestive enzymes.

Use Fig. 4.1 to complete these sentences:

The enzyme with the lowest optimum pH is enzyme …….

The two enzymes with the same optimum pH are enzymes …… and …….

The enzyme that works best in neutral conditions is enzyme …….

▶️Answer/Explanation

The enzyme with the lowest optimum pH is enzyme B.

The two enzymes with the same optimum pH are enzymes A and C.

The enzyme that works best in neutral conditions is enzyme E.

(b) Name one factor, other than pH, that affects enzyme activity.

▶️Answer/Explanation

Temperature.

(c) Complete this definition of an enzyme.

Enzymes are proteins that function as …… catalysts.

▶️Answer/Explanation

Biological.

(d) Carbohydrate, protein and fat are made from chemical elements. Place ticks (✓) in the boxes in Table 4.1 to show all the correct elements each substance is made from.

Substance	Carbon	Hydrogen	Oxygen	Nitrogen
Carbohydrate
Protein
Fat

▶️Answer/Explanation

Table 4.1:

Substance	Carbon	Hydrogen	Oxygen	Nitrogen
Carbohydrate	✓	✓	✓
Protein	✓	✓	✓	✓
Fat	✓	✓	✓

(e)(i) Starch is a carbohydrate. State the name of the smaller molecules that starch is made from.

▶️Answer/Explanation

Glucose.

(ii) Circle the name of one other carbohydrate.

amino acid      fatty acid      glycogen oil

▶️Answer/Explanation

Glycogen.