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Secondary 4 Combined Science Biology Human Physiology Quiz
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Questions
Secondary 4 Combined Science Biology Quiz - Human Physiology
Name: __________________________
Class: __________________________
Date: __________________________
Score: _________ / 45
Duration: 45 minutes
Total Marks: 45
Instructions:
- Answer all questions.
- Write your answers in the spaces provided.
- The number of marks is indicated in brackets [ ] at the end of each question or part question.
- You may use a calculator.
Section A: Nutrition and Enzymes (Questions 1–5)
1. State the end-products of the digestion of proteins. [1]
2. Explain why bile is considered a digestive juice but does not contain enzymes. [2]
3. Figure 1 shows the effect of pH on the activity of two enzymes, Enzyme X and Enzyme Y.
(Imagine a graph where Enzyme X peaks at pH 2 and Enzyme Y peaks at pH 8)
(a) Identify which enzyme is likely found in the stomach. [1]
(b) Explain what happens to Enzyme X if the pH is increased to 7. [2]
4. A student investigates the effect of temperature on the rate of starch digestion by amylase. The results are shown below:
| Temperature (°C) | Time taken for starch to disappear (s) |
|---|---|
| 20 | 180 |
| 30 | 90 |
| 40 | 45 |
| 50 | 120 |
| 60 | >300 (starch remains) |
(a) Calculate the rate of reaction at 40°C (Rate = 1/time). Give your answer to 3 decimal places. [1]
Rate = ____________________ s⁻¹
(b) Explain the difference in the rate of reaction between 40°C and 60°C. [3]
5. Describe the function of the villi in the small intestine. In your answer, explain how their structure aids this function. [3]
Section B: Transport in Humans (Questions 6–10)
6. Name the blood vessel that carries oxygenated blood from the lungs to the heart. [1]
7. State two differences between the structure of an artery and a vein. [2]
8. Figure 2 shows a trace of an electrocardiogram (ECG).
(Imagine a standard P-QRS-T wave trace)
(a) Which part of the heart initiates the heartbeat? [1]
(b) Explain why the left ventricle has a thicker muscular wall than the right ventricle. [2]
9. Table 1 shows the composition of blood plasma, tissue fluid, and lymph.
| Substance | Plasma (g/100cm³) | Tissue Fluid (g/100cm³) | Lymph (g/100cm³) |
|---|---|---|---|
| Protein | 7.0 | 0.2 | 2.5 |
| Glucose | 0.1 | 0.1 | 0.1 |
| Urea | 0.03 | 0.03 | 0.03 |
(a) Explain why the protein concentration is much lower in tissue fluid than in plasma. [2]
(b) Suggest why lymph contains more protein than tissue fluid. [1]
10. Describe the role of platelets in the body. [2]
Section C: Respiration and Gas Exchange (Questions 11–15)
11. Define aerobic respiration using a word equation. [2]
12. State the location of gas exchange in the human respiratory system. [1]
13. Explain how the structure of the alveoli is adapted for efficient gas exchange. Give two features. [2]
14. During strenuous exercise, muscle cells may respire anaerobically.
(a) Write the word equation for anaerobic respiration in human muscle cells. [1]
(b) Explain why anaerobic respiration yields less energy than aerobic respiration. [1]
15. Describe the mechanism of breathing in (inspiration). Include the role of the diaphragm and intercostal muscles. [3]
Section D: Homeostasis and Excretion (Questions 16–20)
16. Define homeostasis. [1]
17. Figure 3 shows the changes in blood glucose concentration after a meal.
(Imagine a graph showing a rise in glucose, followed by a drop back to baseline)
(a) Name the hormone responsible for lowering blood glucose concentration. [1]
(b) Describe how this hormone lowers blood glucose concentration. [2]
18. State the main excretory product produced by the kidneys. [1]
19. Explain the process of ultrafiltration in the kidney. [2]
20. A person moves from a cool room to a hot environment. Describe two ways the skin helps to regulate body temperature in the hot environment. [4]
*** End of Quiz ***
Answers
Secondary 4 Combined Science Biology Quiz - Human Physiology (Answer Key)
1. Amino acids [1]
2.
- Bile does not break down food chemically (no enzymes) [1].
- It emulsifies fats (physical digestion) to increase surface area for lipase action [1].
3.
(a) Enzyme X [1]
(b)
- The enzyme is denatured [1].
- The shape of the active site changes [1], so the substrate can no longer bind (no enzyme-substrate complexes formed).
4.
(a) 1/45 = 0.022 s⁻¹ [1]
(b)
- At 60°C, the high temperature breaks the bonds holding the enzyme structure [1].
- The active site changes shape/is denatured [1].
- Substrate cannot fit into the active site, so the rate drops to zero/near zero [1].
5.
- Function: Absorption of digested food/nutrients [1].
- Adaptation 1: Large surface area due to finger-like projection/microvilli for faster absorption [1].
- Adaptation 2: Thin wall (one cell thick) for short diffusion distance [1]. (Accept: Rich blood supply to maintain concentration gradient)
6. Pulmonary vein [1]
7. Any two of the following [1 each]:
- Arteries have thicker muscular walls; veins have thinner walls.
- Arteries have no valves (except semi-lunar); veins have valves to prevent backflow.
- Arteries have a smaller lumen relative to wall thickness; veins have a larger lumen.
8.
(a) Sino-atrial node (SAN) / Pacemaker [1]
(b)
- Left ventricle pumps blood to the whole body (systemic circulation) [1].
- This requires higher pressure to overcome greater resistance/distance compared to the right ventricle which only pumps to the lungs [1].
9. (a)
- Proteins are large molecules [1].
- They cannot pass through the pores of the capillary walls during ultrafiltration [1].
(b) Lymph is formed from tissue fluid that enters lymph capillaries; some plasma proteins leak into tissue fluid and are collected by lymph vessels [1].
10.
- Platelets help in blood clotting [1].
- They release chemicals/fibrinogen to form a mesh/clot to stop bleeding and prevent entry of pathogens [1].
11. Glucose + Oxygen → Carbon dioxide + Water (+ Energy) [2]
(1 mark for correct reactants, 1 mark for correct products)
12. Alveoli (in the lungs) [1]
13. Any two of the following [1 each]:
- Thin walls (one cell thick) for short diffusion distance.
- Large surface area (many alveoli) for faster diffusion.
- Moist surface to allow gases to dissolve.
- Rich blood supply to maintain concentration gradient.
14.
(a) Glucose → Lactic acid (+ Energy) [1]
(b) Glucose is not completely broken down/oxidized [1].
15.
- External intercostal muscles contract; internal intercostal muscles relax [1].
- Diaphragm contracts and flattens [1].
- Volume of thoracic cavity increases, pressure decreases, air rushes in [1].
16. The maintenance of a constant internal environment within the body [1].
17.
(a) Insulin [1]
(b)
- Insulin causes glucose to move from blood into liver and muscle cells [1].
- Glucose is converted to glycogen for storage [1].
18. Urea [1]
19.
- High pressure in the glomerulus forces small molecules out of the blood [1].
- Small molecules (water, urea, glucose, salts) pass into the Bowman’s capsule; large molecules (proteins, blood cells) remain in the blood [1].
20.
- Vasodilation: Arterioles near the skin surface dilate/widen [1]. More blood flows to the skin surface, allowing more heat to be lost by radiation/convection [1].
- Sweating: Sweat glands produce more sweat [1]. As sweat evaporates, it takes heat energy from the body, cooling the skin/blood [1].