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Secondary 3 Biology Human Physiology Quiz
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Questions
Secondary 3 Biology Quiz - Human Physiology
Name: ___________________________
Class: ___________________________
Date: ___________________________
Score: ________ / 50
Duration: 60 minutes
Total Marks: 50
Instructions:
- Answer ALL questions in the spaces provided.
- Write your answers clearly and in complete sentences where required.
- The number of marks for each question is shown in brackets [ ].
- Where diagrams are referenced, refer to the information given in the question.
- You may use a calculator where necessary.
Section A: Multiple Choice Questions (10 marks)
Questions 1–10: Choose the most accurate answer. Each question carries 1 mark.
1. Which component of blood is primarily responsible for transporting oxygen from the lungs to body tissues?
A. Plasma
B. White blood cells
C. Red blood cells
D. Platelets
Answer: ________ [1]
2. In which part of the human digestive system is pepsin most active?
A. Mouth
B. Stomach
C. Small intestine
D. Large intestine
Answer: ________ [1]
3. Which structure in the heart prevents the backflow of blood from the left ventricle to the left atrium?
A. Tricuspid valve
B. Semilunar valve
C. Bicuspid (mitral) valve
D. Pulmonary valve
Answer: ________ [1]
4. During gas exchange in the alveoli, oxygen moves from the alveolar air into the blood by which process?
A. Active transport
B. Osmosis
C. Diffusion
D. Facilitated diffusion
Answer: ________ [1]
5. Which of the following is a function of the large intestine?
A. Absorption of amino acids
B. Absorption of water and mineral salts
C. Secretion of bile
D. Digestion of fats
Answer: ________ [1]
6. A person's blood glucose level rises after a meal. Which hormone is released to bring the blood glucose level back to normal?
A. Glucagon
B. Adrenaline
C. Insulin
D. Thyroxine
Answer: ________ [1]
7. Which blood vessel carries oxygenated blood away from the heart to the rest of the body?
A. Pulmonary artery
B. Pulmonary vein
C. Aorta
D. Vena cava
Answer: ________ [1]
8. Where does the majority of chemical digestion and nutrient absorption occur in the human digestive system?
A. Stomach
B. Oesophagus
C. Small intestine
D. Large intestine
Answer: ________ [1]
9. Which part of the human brain is responsible for controlling balance and coordination?
A. Cerebrum
B. Cerebellum
C. Medulla oblongata
D. Hypothalamus
Answer: ________ [1]
10. In the human excretory system, ultrafiltration occurs in which structure?
A. Loop of Henle
B. Collecting duct
C. Bowman's capsule
D. Renal vein
Answer: ________ [1]
Section B: Structured Questions (25 marks)
Questions 11–15: Answer in the spaces provided. Show your working or reasoning where required.
11. The diagram below represents a section through the human heart.
(Diagram description for reference: A simplified cross-section of the heart showing four chambers — right atrium, right ventricle, left atrium, left ventricle — with major blood vessels attached. The right side is labelled X and the left side is labelled Y.)
(a) Identify the blood vessel that carries deoxygenated blood from the heart to the lungs. [1]
(b) State two structural differences between the left ventricle and the right ventricle. [2]
(i) _____________________________________________________________
(ii) _____________________________________________________________
(c) Explain why the wall of the left ventricle is thicker than the wall of the right ventricle. [2]
12. A student investigated the effect of exercise on the breathing rate of a person. The results are shown in the table below.
| Time (min) | Breathing rate at rest (breaths/min) | Breathing rate after 2 min of exercise (breaths/min) | Breathing rate 5 min after exercise (breaths/min) |
|---|---|---|---|
| 0 | 14 | — | — |
| 2 | — | 28 | — |
| 7 | — | — | 16 |
(a) State the breathing rate of the person at rest. [1]
(b) Calculate the percentage increase in breathing rate from rest to after 2 minutes of exercise. Show your working. [2]
(c) Explain why the breathing rate increases during exercise. [3]
(d) The breathing rate 5 minutes after exercise is still higher than the resting rate. Suggest a reason for this. [1]
13. The diagram shows a longitudinal section of a villus in the small intestine.
(Diagram description: A single villus showing the outer layer of epithelial cells, a network of blood capillaries inside, and a central lacteal. Arrows indicate the direction of nutrient absorption.)
(a) Name the structure labelled Z (the central vessel within the villus that absorbs fatty acids and glycerol). [1]
(b) Explain two ways in which the structure of a villus is adapted for efficient absorption of digested food. [2]
(i) _____________________________________________________________
(ii) _____________________________________________________________
(c) State where in the digestive system the following nutrients are absorbed after digestion. [2]
(i) Amino acids: _____________________________________________________________
(ii) Fatty acids and glycerol: _____________________________________________________________
14. The graph below shows the changes in blood glucose concentration of a healthy person over a 4-hour period after consuming a glucose drink.
(Graph description: The x-axis shows time in hours (0 to 4). The y-axis shows blood glucose concentration in arbitrary units. The graph starts at a normal level at time 0, rises sharply to a peak at 0.5 hours, then gradually falls back to the normal level by approximately 2.5 hours, and remains stable thereafter.)
(a) State the time at which the blood glucose concentration was at its highest. [1]
(b) Describe the trend in blood glucose concentration from 0 to 0.5 hours. [1]
(c) Explain the role of the liver in bringing the blood glucose concentration back to normal after the peak. [3]
(d) Name the hormone responsible for the decrease in blood glucose concentration after the peak. [1]
15. The diagram shows a simplified drawing of the human urinary system.
(Diagram description: The urinary system showing two kidneys, two ureters, the bladder, and the urethra. The left kidney is labelled P, the tube connecting the kidney to the bladder is labelled Q, and the bladder is labelled R.)
(a) Identify structures P, Q, and R. [3]
P: _____________________________________________________________
Q: _____________________________________________________________
R: _____________________________________________________________
(b) Describe the process of ultrafiltration in the kidney. In your answer, refer to the structures involved and the forces that drive the process. [3]
Section C: Free Response Questions (15 marks)
Questions 16–20: Answer in the spaces provided. Use complete sentences and biological terms where appropriate.
16. Explain how the structure of an alveolus is adapted for efficient gas exchange. In your answer, refer to at least four structural features and explain how each feature aids gas exchange. [4]
17. Describe the path of blood flow through the human circulatory system, starting from the vena cava and returning to the vena cava. In your answer, name all the major chambers, valves, and blood vessels involved, and state whether the blood is oxygenated or deoxygenated at each stage. [5]
18. A person eats a meal containing rice (starch), chicken (protein), and butter (fat). Describe how each of these food substances is digested in the human alimentary canal. In your answer, name the enzymes involved, where they are produced, the conditions required for their action, and the end products of digestion. [6]
19. Explain how the human body maintains a constant internal body temperature when the external environment becomes very hot. In your answer, refer to the role of the skin, the nervous system, and the concept of negative feedback. [5]
20. A patient is found to have a blockage in one of the coronary arteries. Explain the effects this blockage would have on the heart and the rest of the body. In your answer, refer to the function of coronary arteries, the consequences of reduced blood supply to the heart muscle, and the potential effects on other organs. [5]
Answers
Secondary 3 Biology Quiz - Human Physiology
Answer Key
Section A: Multiple Choice Questions
1. C — Red blood cells [1]
Explanation: Red blood cells contain haemoglobin, which binds to oxygen in the lungs and transports it to body tissues. Plasma transports dissolved substances but not oxygen directly. White blood cells are involved in immunity, and platelets in blood clotting.
Common mistake: Students may select A (plasma) because they associate blood transport with the liquid component, but oxygen is primarily carried by haemoglobin within red blood cells.
2. B — Stomach [1]
Explanation: Pepsin is a protease enzyme that works optimally in acidic conditions (pH 1.5–2.0), which are found in the stomach due to hydrochloric acid secretion. In the mouth, the pH is near neutral, and in the small intestine, the pH is alkaline, both of which would denature pepsin.
3. C — Bicuspid (mitral) valve [1]
Explanation: The bicuspid (mitral) valve is located between the left atrium and the left ventricle. It prevents backflow of oxygenated blood into the left atrium when the left ventricle contracts. The tricuspid valve is on the right side of the heart. Semilunar valves are found at the base of the aorta and pulmonary artery.
4. C — Diffusion [1]
Explanation: Oxygen moves from a region of higher concentration (alveolar air) to a region of lower concentration (blood in the capillary) across the thin alveolar and capillary walls. This is a passive process and does not require energy (active transport) or a semipermeable membrane (osmosis).
5. B — Absorption of water and mineral salts [1]
Explanation: The large intestine (colon) absorbs remaining water and mineral salts from undigested food material, forming faeces. Amino acids are absorbed in the small intestine. Bile is produced by the liver, not the large intestine. Fat digestion occurs in the small intestine.
6. C — Insulin [1]
Explanation: Insulin is secreted by the beta cells of the pancreas when blood glucose levels rise after a meal. It stimulates cells (especially liver and muscle cells) to take up glucose and convert it to glycogen for storage, thereby lowering blood glucose concentration. Glucagon has the opposite effect (raises blood glucose).
7. C — Aorta [1]
Explanation: The aorta is the largest artery in the body and carries oxygenated blood from the left ventricle to the rest of the body. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. The pulmonary vein carries oxygenated blood from the lungs to the left atrium. The vena cava carries deoxygenated blood from the body to the right atrium.
8. C — Small intestine [1]
Explanation: The small intestine is the primary site for both chemical digestion (by enzymes from the pancreas and intestinal wall) and nutrient absorption (through villi and microvilli). The stomach mainly digests proteins. The oesophagus is a transport tube with no significant digestive or absorptive function.
9. B — Cerebellum [1]
Explanation: The cerebellum is responsible for balance, coordination of voluntary movements, and posture. The cerebrum controls higher functions such as thinking, memory, and voluntary actions. The medulla oblongata controls involuntary actions like breathing and heart rate. The hypothalamus regulates body temperature and hormone secretion.
10. C — Bowman's capsule [1]
Explanation: Ultrafiltration occurs in the Bowman's capsule (also called the glomerular capsule) in the nephron of the kidney. High blood pressure in the glomerulus forces small molecules (water, glucose, urea, mineral salts) out of the blood and into the Bowman's capsule. The Loop of Henle and collecting duct are involved in reabsorption, not filtration.
Section B: Structured Questions
11.
(a) Pulmonary artery [1]
(b) Two structural differences: [2 — 1 mark each]
(i) The wall of the left ventricle is thicker than the wall of the right ventricle.
(ii) The left ventricle has a more muscular/ thicker muscular wall compared to the right ventricle.
Accept any two valid structural differences, e.g., shape differences, volume differences.
(c) The left ventricle has a thicker wall because it needs to generate greater pressure to pump oxygenated blood to all parts of the body (systemic circulation), which is a much longer distance. [1] The right ventricle only pumps deoxygenated blood to the lungs (pulmonary circulation), which is a shorter distance and requires less pressure. [1]
Marking note: Award 1 mark for stating greater pressure/longer distance, 1 mark for contrasting with the right ventricle/shorter distance to lungs.
12.
(a) 14 breaths per minute [1]
(b) Percentage increase = [(28 − 14) / 14] × 100% [1]
= (14 / 14) × 100%
= 100% [1]
Marking note: Award 1 mark for correct formula/working, 1 mark for correct final answer. Accept if student shows (28−14)/14 × 100 = 100%.
(c) During exercise, muscle cells respire at a faster rate to release more energy for contraction. [1] This increases the concentration of carbon dioxide in the blood. [1] The brain detects the increased CO₂ level and sends nerve impulses to the intercostal muscles and diaphragm, causing them to contract and relax more rapidly, thus increasing the breathing rate. [1] This allows more oxygen to be taken in and more carbon dioxide to be removed.
Marking note: Award 1 mark for increased respiration/energy demand, 1 mark for increased CO₂ detected, 1 mark for nerve impulses to breathing muscles / increased gas exchange.
(d) The body needs to repay the oxygen debt (or remove accumulated lactic acid produced during anaerobic respiration). [1]
Accept: "The body is still removing excess CO₂" or "The muscles are still recovering and require extra oxygen."
13.
(a) Lacteal [1]
(b) Two adaptations: [2 — 1 mark each]
(i) The villus has a thin epithelial wall (one cell thick), which provides a short diffusion distance for nutrients to pass through into the blood capillaries.
(ii) The villus contains a dense network of blood capillaries, which maintains a concentration gradient for efficient absorption by quickly transporting absorbed nutrients away.
Accept: "The villus has a large surface area due to its finger-like shape" or "The presence of a lacteal for absorption of fatty acids and glycerol."
(c) [2 — 1 mark each]
(i) Amino acids: Small intestine (ileum)
(ii) Fatty acids and glycerol: Small intestine (ileum) — absorbed into the lacteal within the villus
Marking note: "Small intestine" alone is acceptable for both. Award full marks if "ileum" is specified.
14.
(a) 0.5 hours (or 30 minutes) [1]
(b) The blood glucose concentration increased sharply/rapidly from the normal level to the peak value. [1]
(c) When blood glucose concentration rises above normal, the pancreas detects the increase and releases insulin from its beta cells. [1] Insulin stimulates the liver to convert excess glucose into glycogen (glycogenesis) for storage. [1] Insulin also increases the rate of glucose uptake by body cells for respiration. [1] These actions collectively bring the blood glucose concentration back to the normal level.
Marking note: Award 1 mark for insulin release, 1 mark for conversion to glycogen in liver, 1 mark for glucose uptake by cells / respiration.
(d) Insulin [1]
15.
(a) [3 — 1 mark each]
P: Kidney
Q: Ureter
R: Bladder
(b) Ultrafiltration occurs in the glomerulus, which is a network of capillaries inside the Bowman's capsule. [1] The diameter of the afferent arteriole is wider than that of the efferent arteriole, which creates high blood pressure in the glomerulus. [1] This high pressure forces small molecules such as water, glucose, urea, and mineral salts out of the blood, through the capillary walls and into the Bowman's capsule. [1] Large molecules such as proteins and blood cells are too large to pass through and remain in the blood.
Marking note: Award 1 mark for location (glomerulus/Bowman's capsule), 1 mark for high pressure mechanism, 1 mark for substances filtered / size-based selection.
Section C: Free Response Questions
16. [4 — 1 mark per valid feature + explanation]
Expected points (any four):
-
Thin alveolar wall (one cell thick / squamous epithelium) — provides a short diffusion distance for gases to pass through quickly.
-
Dense network of blood capillaries surrounding each alveolus — maintains a steep concentration gradient of oxygen and carbon dioxide by continuously carrying blood to and from the alveolus.
-
Large surface area — the presence of millions of alveoli provides a huge total surface area for gas exchange, increasing the rate at which oxygen and carbon dioxide are exchanged.
-
Moist inner surface of the alveolus — gases (oxygen and carbon dioxide) dissolve in the moisture before diffusing across the membrane, which facilitates diffusion.
-
Rich blood supply — the extensive capillary network ensures that oxygenated blood is quickly carried away and deoxygenated blood is brought to the alveoli, maintaining the concentration gradient.
Marking note: Award 1 mark for each correctly named structural feature with a valid explanation of how it aids gas exchange. Feature alone without explanation = 0 marks. Maximum 4 marks.
17. [5 — distributed as follows]
Expected pathway:
-
Vena cava → Right atrium (deoxygenated blood) [1]
-
Right atrium → Tricuspid valve → Right ventricle (deoxygenated blood) [1]
-
Right ventricle → Pulmonary valve → Pulmonary artery → Lungs (deoxygenated blood; gas exchange occurs in the lungs) [1]
-
Lungs → Pulmonary vein → Left atrium (oxygenated blood) [1]
-
Left atrium → Bicuspid (mitral) valve → Left ventricle → Aortic valve → Aorta → Body tissues (oxygenated blood; oxygen is delivered to tissues) → Vena cava (deoxygenated blood returns) [1]
Marking note: Award 1 mark for each correctly described stage with the correct blood vessel/chamber/valve and oxygenation state. The answer must show a complete circuit. If a student correctly names all structures but omits oxygenation state at one stage, deduct 0.5 marks (round down). Maximum 5 marks.
18. [6 — 2 marks per food substance]
Starch (from rice):
- Digestion begins in the mouth where salivary amylase (produced by the salivary glands) breaks down starch into maltose. [1] This occurs at neutral to slightly alkaline pH (around pH 7).
- In the small intestine, pancreatic amylase (from the pancreas) continues starch digestion, and maltase (from the intestinal wall) breaks maltose into glucose. [1]
Protein (from chicken):
- Digestion begins in the stomach where pepsin (produced by gastric glands) breaks down proteins into polypeptides/peptides. [1] This occurs in acidic conditions (pH 1.5–2.0) provided by hydrochloric acid.
- In the small intestine, trypsin (from the pancreas) continues protein digestion, and peptidases (from the intestinal wall) break peptides into amino acids. [1] This occurs in alkaline conditions (pH 8–9).
Fat (from butter):
- Fat digestion occurs mainly in the small intestine. Bile (produced by the liver, stored in the gall bladder) emulsifies fats, breaking large fat globules into smaller droplets to increase the surface area. [1] Lipase (from the pancreas) then breaks down fats into fatty acids and glycerol. [1] This occurs in alkaline conditions (pH 8–9).
Marking note: For each food substance, award 1 mark for naming the correct enzyme(s) and site of production, and 1 mark for stating the correct conditions and end product(s). Maximum 2 marks per substance, 6 marks total.
19. [5 — distributed as follows]
Expected answer:
When the external temperature rises, temperature receptors in the skin detect the increase in body temperature. [1] Nerve impulses are sent to the hypothalamus in the brain, which acts as the body's thermostat. [1] The hypothalamus sends nerve impulses to effectors in the skin to bring about cooling responses:
- Sweat glands produce more sweat; as sweat evaporates from the skin surface, it removes heat, cooling the body. [1]
- Blood vessels (arterioles) in the skin dilate (vasodilation), increasing blood flow to the skin surface, allowing more heat to be lost by radiation to the surroundings. [1]
When the body temperature returns to normal, the hypothalamus reduces the cooling responses. This is an example of negative feedback, where the response counteracts the original stimulus to restore the body to its normal state. [1]
Marking note: Award 1 mark for detection by receptors, 1 mark for role of hypothalamus, 1 mark for sweating/evaporation, 1 mark for vasodilation/heat loss by radiation, 1 mark for negative feedback concept. Maximum 5 marks.
20. [5 — distributed as follows]
Expected answer:
The coronary arteries supply the heart muscle (cardiac muscle) with oxygenated blood and nutrients needed for continuous contraction. [1] A blockage in a coronary artery reduces or cuts off the blood supply to part of the heart muscle. [1] Without sufficient oxygen, the affected heart muscle cells cannot respire aerobically and may die, leading to a heart attack (myocardial infarction). [1] This weakens the heart's ability to pump blood effectively around the body. [1] As a result, other organs and tissues receive less oxygen and nutrients, which can cause symptoms such as shortness of breath, fatigue, dizziness, and in severe cases, organ failure or death. [1]
Marking note: Award 1 mark for function of coronary arteries, 1 mark for reduced blood supply to heart muscle, 1 mark for heart attack / cell death, 1 mark for weakened pumping ability, 1 mark for effects on other organs. Maximum 5 marks.