Home / IB DP Biology- C1.1 Enzymes and metabolism IB Style Questions For HL Paper 1

IB DP Biology- C1.1 Enzymes and metabolism IB Style Questions For HL Paper 1-FA 2025

IBDP Biology HL Paper 1 -FA 2025- All Chapters

Question

The graph shows the activity of an enzyme as temperature increases.

What explains the change in enzyme activity between X and Y?

(A) The enzyme is denaturing as the active site changes shape.
(B) Increased collisions occur as molecules are moving faster.
(C) Increased product concentration speeds up the reaction.
(D) An inhibitor has been added, reducing the number of active sites.

▶️ Answer/Explanation
Between X and Y, enzyme activity increases because temperature rise causes molecules to move faster, resulting in more frequent and energetic collisions between enzyme and substrate molecules. This increases the rate of successful enzyme-substrate interactions.
✅ Answer: (B)

Question

What is an example of an intracellular enzyme-catalysed reaction?

(A) Chemical digestion in the gut
(B) Glycolysis in cellular respiration
(C) Blood clotting in the circulatory system
(D) Recycling of acetylcholine in a synapse

▶️ Answer/Explanation
Intracellular enzymes function within the cell to catalyse metabolic reactions. Glycolysis occurs inside the cytoplasm of cells and involves multiple enzyme-catalysed reactions that break down glucose to release energy.
✅ Answer: (B)

Question

The three-toed sloth, Bradypus variegatus, lives in treetops where it feeds on leaves. It also feeds on algae and fungi which live in its fur.

In which trophic group should the three-toed sloth be classified?

A. Autotroph

B. Consumer

C. Detritivore

D. Saprotroph

▶️Answer/Explanation

Answer: B. Consumer

Explanation:

What are trophic groups?
Trophic groups describe how organisms get their food. Autotrophs make their own food (like plants). Consumers eat other organisms. Detritivores feed on dead material. Saprotrophs break down dead organic matter using external enzymes.

A. Incorrect – Autotrophs make their own food using sunlight or chemicals. The sloth does not do this.
B. Correct – The sloth feeds on living plant material (leaves) and also on algae and fungi. This means it consumes other living organisms, so it’s a consumer.
C. Incorrect – Detritivores eat dead material (like earthworms). The sloth eats living things, not dead material.
D. Incorrect – Saprotrophs (like fungi and bacteria) break down dead organisms using enzymes. The sloth does not do this.

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