Secondary 4 Pure Biology Human Physiology Quiz

Secondary 4 Pure Biology Quiz - Human Physiology: Answer Key

Total Marks: 40
Topic: Human Physiology

Section A: Short Answer

1. Pulmonary vein. [1]
Teaching note: The pulmonary vein is the only vein that carries oxygenated blood (from lungs to left atrium). Common mistake: writing “aorta” (artery, not from lungs).

2. Absorption of water / formation of faeces. [1]
Teaching note: Large intestine reabsorbs water and minerals; stores undigested material.

3. Medulla oblongata. [1]
Teaching note: Part of brainstem controlling autonomic functions including breathing.

4. Ultrafiltration. [1]
Teaching note: High pressure in glomerulus forces water, ions, glucose, amino acids into Bowman’s capsule.

5. Red blood cell (erythrocyte). [1]
Teaching note: Contains haemoglobin which binds O₂.

Section B: Structured Response

6. (a) Breaks down starch into maltose (or sugars). [1]
(b) Salivary glands (mouth). [1]
Teaching note: Amylase secreted in saliva; pancreatic amylase later in duodenum.

7. [3] Mark breakdown:

• Large surface area due to folds/villi/microvilli (1)
• Thin wall (one cell thick) for short diffusion distance (1)
• Rich blood capillary network to maintain concentration gradient (1)
  Teaching note: These adaptions speed up diffusion of nutrients into blood.

8. [3]

• Hypothalamus detects low water potential of blood (1)
• Stimulates pituitary to release ADH (1)
• ADH makes kidney collecting ducts more permeable, more water reabsorbed (1)
  Teaching note: Negative feedback restores osmoregulation.

9. (a) Number of heart beats per minute. [1]
(b) [2] Exercise needs more O₂ and produces more CO₂; heart pumps faster to deliver O₂ and remove CO₂. (2 marks for linking need to rate)
Teaching note: Pulse = arterial expansion from ventricular contraction.

10. [3]

• CO₂ diffuses from tissues into plasma (1)
• Some converted to hydrogencarbonate ions (HCO₃⁻) in RBC (1)
• Transported in plasma to lungs, reconverted, exhaled (1)
  Teaching note: ~70% as HCO₃⁻, ~20% carbamino, ~10% dissolved.

Section C: Data & Diagram Interpretation

11. (a) Left ventricle. [1]
(b) Thick muscular wall to pump blood to whole body. [1]
Teaching note: Left side thicker than right because systemic circulation needs higher pressure.

12. [2] Fetal haemoglobin has higher affinity for O₂; at low partial pressure in placenta it loads O₂ from maternal blood.
Teaching note: Curve left-shifted; ensures O₂ transfer to fetus.

13. (a) % increase = (7.2 – 4.5)/4.5 × 100 = 2.7/4.5 × 100 = 60%. [2]
(b) Insulin. [1]
Teaching note: Show subtraction then divide by original.

14. [2] Ultrafiltration at P; glucose (or amino acids, ions, water) reabsorbed at Q. [2]
Teaching note: P = Bowman’s capsule; Q = proximal tubule selective reabsorption.

15. [3]

• Exercise increases respiration, more CO₂ produced (1)
• Need to remove CO₂ and take in more O₂ (1)
• Higher breathing rate increases alveolar ventilation (1)
  Teaching note: Links to gas exchange efficiency.

16. (a) Sensory neuron. [1]
(b) Relays impulse from sensory to motor neuron in spinal cord. [1]
Teaching note: Enables rapid reflex without brain.

17. (a) T wave. [1]
(b) Rate = 60 / 0.8 = 75 beats/min. [2]
Teaching note: One cycle 0.8 s; 60 s ÷ 0.8.

18. [3]

• External intercostal muscles contract, ribcage up/out (1)
• Diaphragm contracts, flattens (1)
• Thoracic volume increases, pressure drops, air in (1)
  Teaching note: Active process of inhalation.

19. [2] Outward (to tissues); hydrostatic pressure (4.0) > osmotic (3.0).
Teaching note: Net outward filtration at arterial end.

20. [3]

• Consequence: reduced bile production (1)
• Explanation: bile emulsifies fats; less bile → poor fat digestion (2)
  Teaching note: Liver also detoxifies; other valid answers accepted with reason.