Secondary 4 Pure Biology Human Physiology Quiz

Secondary 4 Pure Biology Quiz - Human Physiology (Answer Key)

Total Marks: 40
Topic: Human Physiology
Note: Content generated from LLM-inferred Stage 4 templates. Not derived from past-year exam papers; syllabus-aligned practice only.

Section A: Short Answer

1. [1] Peristalsis
Teaching note: Peristalsis is the wave-like contraction of circular and longitudinal muscles in the oesophagus (and other parts of the gut) that pushes food along. Do not confuse with chewing (mechanical digestion) or segmentation.

2. [1] Absorb nutrients (e.g. glucose, amino acids) / increase surface area for absorption.
Teaching note: Villi are finger-like projections of the small intestine wall; they increase surface area and contain capillaries and lacteals for absorption.

3. [1] Insulin
Teaching note: Insulin is released by the pancreas (β-cells of islets of Langerhans) when blood glucose is high; it lowers blood glucose by promoting uptake by liver and muscle.

4. [1] Kidney
Teaching note: Kidneys filter blood; urine is formed in nephrons. The liver detoxifies but does not form urine.

5. [1] Homeostasis
Teaching note: Homeostasis is the maintenance of a constant internal environment (e.g. temperature, pH, glucose) despite external changes.

Section B: Structured Response

6. [3 total]
(a) [1] Liver
(b) [1] Gall bladder
(c) [1] Emulsifies fats / neutralises stomach acid (accept either)
Teaching note: Bile is produced in the liver, stored in gall bladder, released to duodenum. Emulsification breaks large fat droplets into smaller ones to increase surface area for lipase.

7. [3 total]
(a) [1] Left ventricle
(b) [2] Pulmonary artery carries deoxygenated blood; pulmonary vein carries oxygenated blood. (2 marks: one correct statement each)
Teaching note: Unlike most arteries, pulmonary artery carries deoxygenated blood from right ventricle to lungs. Pulmonary vein returns oxygenated blood to left atrium.

8. [3]

• Biconcave shape increases surface area for oxygen diffusion [1]
• No nucleus allows more space for haemoglobin [1]
• Contains haemoglobin to bind oxygen [1]
  Teaching note: Adaptations link structure to function: more haemoglobin = more O₂ carried; biconcave = shorter diffusion distance.

9. [3]

• High blood glucose lowers water potential of blood [1]
• Water moves out of red blood cells by osmosis (down water potential gradient) [1]
• RBCs lose water, shrink (crenate), may be damaged [1]
  Teaching note: Water moves from higher to lower water potential. Lower water potential in blood = water leaves cells. This is the same principle as plasmolysis in plant cells but animal cells crenate.

10. [3 total]
(a) [2] Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration (down concentration gradient).
(b) [1] Oxygen from alveoli to blood / CO₂ from blood to alveoli / glucose from gut to blood (any one).
Teaching note: Must include "net movement" and "down concentration gradient" for full marks.

11. [4]

• Osmoreceptors detect high water content [1]
• Pituitary gland releases less ADH [1]
• Kidney collecting ducts become less permeable to water [1]
• More water lost in urine (dilute urine) [1]
  Teaching note: ADH = antidiuretic hormone. Low ADH = less water reabsorbed = larger volume of dilute urine. This is negative feedback.

12. [3 total]
(a) [1] Sensory neuron (afferent neuron)
(b) [2] Relay neuron connects sensory to motor neuron within spinal cord allowing rapid reflex response without brain involvement.
Teaching note: Reflex arc bypasses brain for speed; relay neuron is in grey matter of spinal cord.

13. [4 total]
(a) [1] Oxygen (O₂)
(b) [3] Thin walls (short diffusion distance) [1]; large surface area (many alveoli) [1]; moist lining (gases dissolve) [1].
Teaching note: Gas exchange needs thin, moist, large surface area — same principle as villi and leaf mesophyll.

Section C: Data and Diagram Interpretation

14. [3 total]
(a) [1] Transpiration rate increases with light intensity.
(b) [2] Stomata open wider in bright light for photosynthesis; more water vapour exits leaves.
Teaching note: Light stimulates guard cells to open stomata; transpiration is water loss from stomata.

15. [4 total]
(a) [1] 150 mg/100 cm³
(b) [3] Insulin released after meal [1]; glucose absorbed by liver/muscle cells [1]; converted to glycogen so blood level falls [1].
Teaching note: Read graph at x=1 h. Drop due to insulin action (homeostasis).

16. [1] Diffusion
Teaching note: O₂ moves from high concentration in capillary to low concentration in cell by diffusion; no energy needed.

17. [4 total]
(a) [2] % decrease = (140 − 78) / 140 × 100 = 62 / 140 × 100 = 44.3% (accept 44%).
Working:
Initial = 140, final = 78
Decrease = 62
% = 62/140 × 100 = 44.3%
(b) [2] Body still recovering; O₂ debt being repaid / remaining adrenaline / temperature still raised.
Teaching note: Show substitution clearly. Pulse stays above resting (≈70) due to continued elevated metabolism.

18. [3 total]
(a) [1] Ultrafiltration
(b) [2] Glucose, amino acids, water, salts (any two named = 2 marks; one = 1 mark).
Teaching note: Filtration forces small molecules into Bowman's capsule; PCT reabsorbs useful molecules actively.

19. [3 total]
(a) [1] Flattens / contracts downward
(b) [2] Flattening increases vertical chest dimension; rib muscles lift ribs outward; total volume increases, pressure falls, air enters.
Teaching note: Inhalation is active; diaphragm contracts. Exhalation is passive recoil.

20. [4 total]
(a) [1] Diabetes mellitus (Type 1)
(b) [3] No insulin produced [1]; glucose cannot enter cells efficiently [1]; remains in blood so concentration rises [1].
Teaching note: Type 1 = autoimmune pancreatic damage. Without insulin, cells cannot take up glucose; kidneys excrete some (glucose in urine).