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Secondary 4 Pure Biology Human Physiology Quiz

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Secondary 4 Pure Biology AI Generated Generated by Qwen3.6 Plus Updated 2026-08-17

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Secondary 4 Pure Biology Quiz - Human Physiology

Name: __________________________
Class: __________________________
Date: ___________________________
Score: ________ / 40

Duration: 45 minutes
Total Marks: 40

Instructions:

Answer all questions.
Write your answers in the spaces provided.
The number of marks available for each question or part question is given in brackets [ ].
This quiz covers Topic: Human Physiology (Nutrition, Transport, Respiration, Excretion, Homeostasis).

Section A: Nutrition and Digestion (Questions 1–4)

1. Fig. 1.1 shows a section of the human alimentary canal.

Image pending generation for this question.

(a) Identify the organ labelled X where protein digestion begins. [1]

(b) State the enzyme responsible for the initial breakdown of proteins in organ X. [1]

2. The villi in the small intestine are adapted for absorption.

(a) State two structural features of a villus that increase the rate of absorption. [2]

(b) Glucose is absorbed into the blood capillaries of the villus. Describe the pathway taken by this glucose to reach the liver. [2]

3. A student investigated the effect of bile on the digestion of fats. Two test tubes were set up:

Tube A: Fat + Lipase + Bile
Tube B: Fat + Lipase + Water

The time taken for the pH to drop was recorded. Tube A showed a faster drop in pH than Tube B.

(a) Explain the role of bile in Tube A. [2]

(b) Why did the pH drop in both tubes? [1]

4. State the primary function of the hepatic portal vein. [1]

Section B: Transport and Respiration (Questions 5–10)

5. Fig. 5.1 shows a cross-section of a blood vessel.

Image pending generation for this question.

(a) Identify this blood vessel. [1]

(b) State one feature visible in the diagram that helps identify this vessel. [1]

6. Table 6.1 shows the composition of blood plasma, tissue fluid, and lymph.

Component	Blood Plasma (%)	Tissue Fluid (%)	Lymph (%)
Protein	7.0	0.5	2.0
Glucose	0.1	0.1	0.1

(a) Explain why the protein concentration in tissue fluid is much lower than in blood plasma. [2]

(b) Describe how lymph is formed from tissue fluid. [2]

7. During vigorous exercise, the heart rate increases.

(a) Name the part of the brain that controls heart rate. [1]

(b) Explain how an increased heart rate benefits muscle cells during exercise. [2]

8. Fig. 8.1 shows the changes in air pressure in the lungs during breathing.

Image pending generation for this question.

(a) During which phase of breathing is the pressure in the lungs lower than atmospheric pressure? [1]

(b) Describe the movements of the diaphragm and rib cage during this phase. [3]

9. Compare aerobic and anaerobic respiration in human muscle cells.

(a) State the end product of anaerobic respiration in humans. [1]

(b) Explain why anaerobic respiration releases less energy per glucose molecule than aerobic respiration. [2]

10. A sprinter experiences "oxygen debt" after a 100m race.

(a) Define oxygen debt. [1]

(b) Explain how the body repays this debt after the race stops. [2]

Section C: Excretion and Homeostasis (Questions 11–16)

11. Fig. 11.1 shows a nephron.

Image pending generation for this question.

(a) Name the process that occurs between structure A and B. [1]

(b) State two substances that are filtered out of the blood at this stage. [2]

12. Explain why glucose is present in the filtrate in the Bowman’s capsule but absent in the urine of a healthy person. [2]

13. A patient with kidney failure undergoes dialysis.

(a) State one similarity between dialysis and the function of a healthy kidney. [1]

(b) State one difference between dialysis and the function of a healthy kidney regarding selectivity. [1]

14. Homeostasis maintains a constant internal environment.

(a) Define homeostasis. [1]

(b) Explain why maintaining a constant body temperature is important for enzyme activity. [2]

15. Fig. 15.1 shows the regulation of blood glucose levels.

(Imagine a flowchart: High Blood Glucose -> Pancreas -> Hormone X -> Liver -> Glucose to Glycogen)

(a) Identify Hormone X. [1]

(b) Describe how Hormone X lowers blood glucose levels. [2]

16. A person moves from a cold room into a hot environment.

(a) Describe the change in the diameter of the arterioles supplying the skin capillaries. [1]

(b) Explain how this change helps to regulate body temperature. [2]

Section D: Coordination and Response (Questions 17–20)

17. Fig. 17.1 shows a reflex arc.

Image pending generation for this question.

(a) Identify the type of neuron labelled Y that connects the sensory and motor neurons. [1]

(b) State the advantage of a reflex action over a voluntary action. [1]

18. Compare nervous coordination and hormonal coordination.

(a) State one difference in the speed of response. [1]

(b) State one difference in the duration of the effect. [1]

19. The eye adjusts to changes in light intensity.

(a) Name the part of the eye that contains the light-sensitive cells. [1]

(b) Describe the pupil reflex when a person moves from a dark room into bright sunlight. Include the muscles involved. [3]

20. Insulin is produced using genetic engineering.

(a) Explain why human insulin produced by bacteria is identical to human insulin. [1]

(b) State one advantage of using genetically engineered insulin over insulin extracted from pigs. [1]

*** End of Quiz ***

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Answers

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

Total Marks: 40

Section A: Nutrition and Digestion

1. (a) Stomach [1] (b) Pepsin [1] (c) The stomach contains hydrochloric acid which creates an acidic pH (pH 1.5-2.0) [1]. Pepsin works optimally in acidic conditions, whereas enzymes in the small intestine (e.g., trypsin) work best in alkaline conditions and would be denatured/inactive in acid [1].

2. (a) Any two of the following: [2]

Thin wall (one cell thick) for short diffusion distance.
Rich blood supply (capillaries) to maintain concentration gradient.
Presence of microvilli to increase surface area.
Lacteal for absorption of fatty acids/glycerol. (b) Glucose enters the capillaries of the villus [1]. It is transported via the hepatic portal vein to the liver [1].

3. (a) Bile emulsifies fats [1]. This breaks large fat droplets into smaller droplets, increasing the surface area for lipase to act on [1]. (b) Lipase breaks down fats into fatty acids and glycerol [1]. Fatty acids are acidic, causing the pH to drop.

4. To transport absorbed nutrients (glucose, amino acids) from the small intestine to the liver [1].

Section B: Transport and Respiration

5. (a) Vein [1] (b) Presence of valves [1] OR Thin wall / Large lumen (if visible). (c) Valves prevent the backflow of blood [1], ensuring blood flows in one direction towards the heart, especially against gravity [1].

6. (a) Large protein molecules are too large to pass through the capillary walls [1]. They remain in the blood plasma, while smaller molecules filter out to form tissue fluid [1]. (b) Tissue fluid enters the blind-ended lymph capillaries [1]. The fluid is then called lymph [1].

7. (a) Medulla (of the brain stem) [1] (b) It increases the rate of blood flow to muscles [1]. This delivers more oxygen and glucose for respiration and removes carbon dioxide/lactic acid faster [1].

8. (a) Inhalation (Inspiration) [1] (b) Diaphragm contracts and flattens [1]. External intercostal muscles contract, pulling ribs up and out [1]. This increases the volume of the thoracic cavity, decreasing pressure [1].

9. (a) Lactic acid [1] (b) Glucose is not completely broken down/oxidized [1]. Much of the energy remains stored in the lactic acid molecule [1].

10. (a) The amount of oxygen required to oxidize the lactic acid accumulated during anaerobic respiration [1]. (b) The person continues to breathe heavily after stopping [1]. This oxygen is used to convert lactic acid back into glucose (in the liver) or oxidize it completely [1].

Section C: Excretion and Homeostasis

11. (a) Ultrafiltration [1] (b) Any two: Water, Glucose, Urea, Salts/Ions [2]. (Do not accept proteins or blood cells).

12. Glucose is small enough to be filtered into the Bowman’s capsule [1]. However, it is completely reabsorbed by active transport in the proximal convoluted tubule [1].

13. (a) Both remove urea/waste products from the blood [1] OR Both use diffusion across a semi-permeable membrane. (b) Dialysis is not selective; it removes small molecules based on concentration gradients only [1]. A healthy kidney selectively reabsorbs useful substances like glucose and adjusts water balance via hormones (ADH).

14. (a) The maintenance of a constant internal environment despite external changes [1]. (b) Enzymes have an optimum temperature (37°C) [1]. If temperature deviates significantly, enzymes may denature (change shape) and metabolic reactions will slow down or stop [1].

15. (a) Insulin [1] (b) Insulin causes the liver to convert glucose into glycogen [1]. This removes glucose from the blood, lowering the concentration [1].

16. (a) Vasodilation (Arterioles widen/dilate) [1]. (b) More blood flows to the skin surface/capillaries [1]. More heat is lost from the blood to the environment by radiation/convection [1].

Section D: Coordination and Response

17. (a) Relay neuron (or Intermediate neuron) [1] (b) Reflex actions are faster/automatic [1], providing immediate protection from harm without conscious thought.

18. (a) Nervous is fast / Hormonal is slow [1]. (b) Nervous is short-lived / Hormonal is long-lasting [1].

19. (a) Retina [1] (b) Circular muscles of the iris contract [1]. Radial muscles of the iris relax [1]. This causes the pupil to constrict (become smaller), reducing the amount of light entering the eye [1].

20. (a) The bacteria use the human gene/DNA code to produce the protein [1]. The genetic code is universal. (b) It is identical to human insulin (less likely to cause allergic reactions) [1] OR It is ethically acceptable (no animals killed) OR It can be produced in large quantities cheaply.