O-Level Combined Science — Biology 3 — Questions and Answers
Question 1: Which part of the cell contains genetic information (DNA)?
- Mitochondria
- Cell membrane
- Nucleus (Correct answer)
- Cytoplasm
Correct answer: Nucleus
The nucleus contains the cell's DNA, organised into chromosomes, which carry genetic information for the cell's functions.
Question 2: What is the function of red blood cells?
- Fight infection
- Carry oxygen (Correct answer)
- Clot blood
- Produce antibodies
Correct answer: Carry oxygen
Red blood cells (erythrocytes) contain haemoglobin, which binds to oxygen in the lungs and carries it to body tissues.
Question 3: What is the term for organisms that break down dead organic matter?
- Producers
- Consumers
- Decomposers (Correct answer)
- Herbivores
Correct answer: Decomposers
Decomposers (such as bacteria and fungi) break down dead organisms and waste materials, recycling nutrients back into the ecosystem.
Question 4: Which vitamin is produced by the skin when exposed to sunlight?
- Vitamin A
- Vitamin B12
- Vitamin C
- Vitamin D (Correct answer)
Correct answer: Vitamin D
Vitamin D is synthesised in the skin when it is exposed to ultraviolet B (UVB) radiation from sunlight. It is essential for calcium absorption.
Question 5: What is the name of the process where plants lose water through their leaves?
- Osmosis
- Transpiration (Correct answer)
- Photosynthesis
- Respiration
Correct answer: Transpiration
Transpiration is the process by which plants lose water vapour through their stomata (pores in leaves). It helps draw water up from the roots.
Question 6: How many chromosomes do human body cells normally contain?
- 23
- 46 (Correct answer)
- 92
- 44
Correct answer: 46
Normal human body (somatic) cells contain 46 chromosomes arranged in 23 pairs. Gametes (sex cells) contain 23 chromosomes.
O-Level Combined Science — Biology 3
Which part of the cell contains genetic information (DNA)?