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O Level Biology Human Physiology Quiz
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Questions
O-Level Biology Quiz - Human Physiology
Name: _________________________ Class: _________________________ Date: _________________________ Score: ______ / 40
Duration: 45 minutes Total Marks: 40
Instructions:
- Answer ALL questions in the spaces provided.
- Write your answers clearly and legibly.
- The number of marks for each question or part question is shown in brackets [ ].
- You are advised to spend no more than 5 minutes on Section A, 15 minutes on Section B, and 25 minutes on Section C.
Section A: Short Answer Questions (5 marks)
Answer all questions in this section.
1. Name the blood vessel that carries deoxygenated blood from the heart to the lungs. [1]
2. State the equation for anaerobic respiration in human muscle cells. [1]
3. Define the term excretion. [1]
4. Name the hormone that stimulates the conversion of glucose to glycogen in the liver. [1]
5. Identify the type of neurone that transmits an impulse from a sensory receptor to the spinal cord. [1]
Section B: Structured Questions (15 marks)
Answer all questions in this section.
6. The diagram below shows a cross-section of a human heart.
(Diagram shows four chambers with arrows indicating blood flow direction.)
(a) Name the chamber labelled X that receives oxygenated blood from the lungs. [1]
(b) Explain why the wall of chamber Y (left ventricle) is thicker than the wall of chamber Z (right ventricle). [2]
(c) State the function of the valves found between the atria and ventricles. [1]
7. A student investigated the effect of exercise on breathing rate. The table below shows the results.
| Condition | Breathing rate (breaths per minute) |
|---|---|
| At rest | 16 |
| After 2 minutes of jogging | 28 |
| 5 minutes after exercise | 18 |
(a) Calculate the percentage increase in breathing rate from rest to immediately after jogging. Show your working. [2]
(b) Explain why breathing rate increases during exercise. [3]
8. The human kidney plays a vital role in excretion and osmoregulation.
(a) Name the functional unit of the kidney where filtration occurs. [1]
(b) Describe the process of ultrafiltration that occurs in the kidney. [3]
(c) Explain how the hormone ADH helps to regulate the water content of the blood. [2]
9. The diagram below shows a reflex arc.
(Diagram shows the pathway of a reflex arc from receptor to effector.)
(a) Name the type of neurone labelled P that is found entirely within the spinal cord. [1]
(b) Explain why reflex actions are faster than voluntary actions. [2]
10. The graph below shows the changes in blood glucose concentration of a healthy person after consuming a glucose-rich meal.
(Graph shows blood glucose concentration (mg/dL) on y-axis against time (hours) on x-axis. The line peaks at 140 mg/dL at 1 hour and returns to baseline by 2.5 hours.)
(a) Describe the changes in blood glucose concentration shown in the graph. [2]
(b) Explain the role of insulin in regulating blood glucose concentration. [2]
Section C: Extended Response Questions (20 marks)
Answer all questions in this section. Your answers should demonstrate clear understanding of biological mechanisms and use appropriate scientific terminology.
11. Describe the pathway taken by a reflex impulse from the moment a stimulus is detected to the response produced. Name all the components of the reflex arc involved. [6]
12. Describe the double circulation of blood in the human circulatory system. In your answer, name the chambers of the heart and the major blood vessels involved, and explain the importance of having two separate circuits. [6]
13. The graph below shows the changes in blood glucose concentration of a healthy person and a person with diabetes after consuming a glucose-rich meal.
(Graph shows blood glucose concentration (mg/dL) on y-axis against time (hours) on x-axis. Two lines: one labelled "Healthy person" peaks at 140 mg/dL at 1 hour and returns to baseline by 2.5 hours; the other labelled "Person with diabetes" peaks at 220 mg/dL at 1.5 hours and remains elevated above 160 mg/dL at 3 hours.)
(a) Compare the changes in blood glucose concentration in the healthy person and the person with diabetes during the 3-hour period. [3]
(b) Explain the role of insulin and glucagon in regulating blood glucose concentration in a healthy person. [3]
(c) Suggest why the blood glucose concentration of the person with diabetes remains elevated for a longer period. [2]
14. Describe the process of gas exchange in the alveoli of the lungs. Explain how the structure of the alveoli is adapted for efficient gas exchange. [4]
15. Explain how the structure of an artery is related to its function of transporting blood away from the heart. [4]
Section D: Data-Based and Application Questions (5 marks)
Answer all questions in this section.
16. A student set up an experiment to investigate the effect of temperature on the rate of respiration in yeast. The table below shows the volume of carbon dioxide produced at different temperatures.
| Temperature (°C) | Volume of CO₂ produced (cm³) |
|---|---|
| 10 | 2 |
| 20 | 5 |
| 30 | 12 |
| 40 | 8 |
| 50 | 1 |
(a) Describe the trend shown by the results. [2]
(b) Explain why the volume of carbon dioxide produced decreases at temperatures above 30°C. [2]
17. The diagram below shows a nephron of the human kidney.
(Diagram shows a nephron with labelled parts including the glomerulus, Bowman's capsule, and collecting duct.)
(a) Name the process that occurs at the glomerulus. [1]
(b) Explain why glucose is not normally found in the urine of a healthy person. [2]
18. A person is diagnosed with a condition that causes the walls of their alveoli to become thickened and less elastic.
(a) Explain how this condition would affect the person's ability to take in oxygen. [2]
(b) Suggest one symptom this person might experience and explain why. [1]
19. The hormone adrenaline is released during times of stress or excitement. Describe the effects of adrenaline on the body and explain how these effects prepare the body for 'fight or flight'. [3]
20. Explain the importance of maintaining a constant internal environment (homeostasis) in the human body. Use the regulation of body temperature as an example in your answer. [3]
END OF QUIZ
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Answers
O-Level Biology Quiz - Human Physiology — Answer Key
Total Marks: 40
Section A: Short Answer Questions (5 marks)
1. Name the blood vessel that carries deoxygenated blood from the heart to the lungs. [1]
Answer: Pulmonary artery
Marking note: Accept "pulmonary arteries". Do not accept "pulmonary vein" (carries oxygenated blood to the heart).
2. State the equation for anaerobic respiration in human muscle cells. [1]
Answer: Glucose → Lactic acid (+ energy)
OR C₆H₁₂O₆ → 2 C₃H₆O₃ (+ 2 ATP)
Marking note: Accept either word or chemical equation. Do not accept "ethanol" or "carbon dioxide" as products (these are products of anaerobic respiration in yeast/plants, not humans). Award mark if "lactate" is used instead of "lactic acid".
3. Define the term excretion. [1]
Answer: Excretion is the removal of metabolic waste products from the body.
Marking note: Must include "metabolic waste products". Do not accept "removal of waste" alone (too vague; could refer to egestion). Accept examples of metabolic wastes (urea, carbon dioxide, excess water, excess salts) as part of the definition.
4. Name the hormone that stimulates the conversion of glucose to glycogen in the liver. [1]
Answer: Insulin
Marking note: Accept only "insulin". Do not accept "glucagon" (stimulates glycogen → glucose conversion).
5. Identify the type of neurone that transmits an impulse from a sensory receptor to the spinal cord. [1]
Answer: Sensory neurone
Marking note: Accept "sensory neuron". Do not accept "motor neurone" or "relay neurone".
Section B: Structured Questions (15 marks)
6. Heart structure and function.
(a) Name the chamber labelled X that receives oxygenated blood from the lungs. [1]
Answer: Left atrium
Marking note: Must state "left atrium". Do not accept "atrium" alone (ambiguous).
(b) Explain why the wall of chamber Y (left ventricle) is thicker than the wall of chamber Z (right ventricle). [2]
Answer:
- The left ventricle pumps blood to the whole body (systemic circulation) [1]
- This requires higher pressure / more force to overcome greater resistance / to pump blood a longer distance [1]
Marking note: Award 1 mark for identifying that the left ventricle pumps blood to the body (systemic circuit), and 1 mark for linking this to the need for higher pressure or greater force. Accept reference to the right ventricle only pumping blood to the lungs (shorter distance, lower pressure).
(c) State the function of the valves found between the atria and ventricles. [1]
Answer: To prevent backflow of blood from the ventricles into the atria.
Marking note: Must mention "prevent backflow". Accept "ensure one-way flow of blood". Do not accept "to pump blood" (valves do not pump).
7. Breathing rate investigation.
(a) Calculate the percentage increase in breathing rate from rest to immediately after jogging. Show your working. [2]
Answer:
- Increase = 28 − 16 = 12 breaths per minute [1]
- Percentage increase = (12 ÷ 16) × 100 = 75% [1]
Marking note: Award 1 mark for correct calculation of the difference, and 1 mark for correct percentage. Accept working shown as (28 − 16)/16 × 100. If answer is correct but no working shown, award full marks. If working is shown but final answer is incorrect, award 1 mark for correct method.
(b) Explain why breathing rate increases during exercise. [3]
Answer:
- During exercise, muscles contract more and require more energy [1]
- More aerobic respiration occurs, requiring more oxygen and producing more carbon dioxide [1]
- Increased breathing rate brings more oxygen into the lungs and removes more carbon dioxide from the blood to meet the increased demand [1]
Marking note: Award marks for: (1) linking exercise to increased energy demand/muscle activity, (2) linking to increased respiration and gas exchange needs, (3) explaining the purpose of increased breathing rate. Accept reference to oxygen debt and removal of lactic acid if linked to continued elevated breathing rate after exercise.
8. Kidney function.
(a) Name the functional unit of the kidney where filtration occurs. [1]
Answer: Nephron
Marking note: Accept "nephron" only. Do not accept "glomerulus" or "Bowman's capsule" (these are parts of the nephron).
(b) Describe the process of ultrafiltration that occurs in the kidney. [3]
Answer:
- Blood enters the glomerulus under high pressure [1]
- The high pressure forces small molecules (water, glucose, amino acids, urea, salts) out of the blood through the capillary walls and into the Bowman's capsule [1]
- Large molecules (proteins, blood cells) remain in the blood as they are too large to pass through [1]
Marking note: Award 1 mark each for: (1) high pressure in glomerulus, (2) small molecules filtered out (must name at least two examples), (3) large molecules retained. Accept reference to the partially permeable basement membrane as the filtration barrier.
(c) Explain how the hormone ADH helps to regulate the water content of the blood. [2]
Answer:
- ADH increases the permeability of the collecting ducts to water [1]
- This allows more water to be reabsorbed from the filtrate back into the blood, reducing urine volume and increasing blood water content [1]
Marking note: Award 1 mark for stating that ADH increases permeability of collecting ducts (or distal convoluted tubule) to water, and 1 mark for explaining the consequence (more water reabsorbed, urine becomes more concentrated, blood water content increases). Accept reference to negative feedback: when blood water content is low, more ADH is released.
9. Reflex arc.
(a) Name the type of neurone labelled P that is found entirely within the spinal cord. [1]
Answer: Relay neurone / Intermediate neurone
Marking note: Accept "relay neurone" or "intermediate neurone". Do not accept "sensory neurone" or "motor neurone".
(b) Explain why reflex actions are faster than voluntary actions. [2]
Answer:
- Reflex actions involve fewer synapses / a shorter neural pathway [1]
- The impulse does not need to travel to the brain for processing / the response is automatic and does not require conscious thought [1]
Marking note: Award 1 mark for mentioning fewer synapses or shorter pathway, and 1 mark for stating that the brain is not involved in the initial response. Accept reference to the reflex arc bypassing the brain.
10. Blood glucose regulation.
(a) Describe the changes in blood glucose concentration shown in the graph. [2]
Answer:
- Blood glucose concentration rises after the meal, reaching a peak of 140 mg/dL at 1 hour [1]
- It then decreases, returning to the baseline level by 2.5 hours [1]
Marking note: Award 1 mark for describing the rise and peak, and 1 mark for describing the fall and return to baseline. Must include reference to the values or times from the graph.
(b) Explain the role of insulin in regulating blood glucose concentration. [2]
Answer:
- Insulin is released by the pancreas when blood glucose concentration is high [1]
- It stimulates the liver and muscle cells to convert glucose to glycogen, lowering blood glucose concentration [1]
Marking note: Award 1 mark for stating when insulin is released (high blood glucose), and 1 mark for describing its effect (conversion of glucose to glycogen). Accept reference to increased permeability of cells to glucose.
Section C: Extended Response Questions (20 marks)
11. Describe the pathway taken by a reflex impulse from the moment a stimulus is detected to the response produced. Name all the components of the reflex arc involved. [6]
Answer:
- Receptor — detects the stimulus (e.g., pain, heat) and generates a nerve impulse [1]
- Sensory neurone — transmits the impulse from the receptor to the spinal cord [1]
- Relay neurone (in the spinal cord) — receives the impulse from the sensory neurone and passes it to the motor neurone via a synapse [1]
- Synapse — neurotransmitter is released from the sensory/relay neurone, diffuses across the synaptic cleft, and binds to receptors on the next neurone, generating a new impulse [1]
- Motor neurone — transmits the impulse from the spinal cord to the effector [1]
- Effector (muscle or gland) — responds to the impulse (e.g., muscle contracts to withdraw hand) [1]
Marking note: Award 1 mark for each correctly named and described component in the correct sequence. The six components are: receptor, sensory neurone, relay neurone, synapse (or spinal cord), motor neurone, effector. Accept "intermediate neurone" for relay neurone. The description of the synapse must include reference to neurotransmitter release and transmission across the synaptic cleft. Do not award marks if the sequence is incorrect or if components are named without description of their role.
12. Describe the double circulation of blood in the human circulatory system. In your answer, name the chambers of the heart and the major blood vessels involved, and explain the importance of having two separate circuits. [6]
Answer: Pulmonary circulation:
- Deoxygenated blood from the body enters the right atrium via the vena cava [1]
- Blood passes to the right ventricle, which pumps it to the lungs via the pulmonary artery [1]
- In the lungs, blood is oxygenated and returns to the left atrium via the pulmonary vein [1]
Systemic circulation: 4. Oxygenated blood passes from the left atrium to the left ventricle, which pumps it to the body via the aorta [1] 5. Blood delivers oxygen and nutrients to body cells and returns deoxygenated blood to the right atrium via the vena cava [1]
Importance: 6. The two separate circuits allow oxygenated and deoxygenated blood to be kept separate, ensuring that blood pumped to the body is fully oxygenated / allows higher pressure in the systemic circuit for efficient delivery of oxygen to tissues [1]
Marking note: Award 1 mark for each of the six points above. Must name the four chambers (right atrium, right ventricle, left atrium, left ventricle) and the major vessels (vena cava, pulmonary artery, pulmonary vein, aorta). The explanation of importance must refer to separation of oxygenated/deoxygenated blood or maintenance of high pressure.
13. Diabetes and blood glucose regulation.
(a) Compare the changes in blood glucose concentration in the healthy person and the person with diabetes during the 3-hour period. [3]
Answer:
- Both show a rise in blood glucose concentration after the meal, but the person with diabetes reaches a higher peak (220 mg/dL vs 140 mg/dL) [1]
- The peak occurs later in the person with diabetes (1.5 hours vs 1 hour) [1]
- The healthy person's blood glucose returns to baseline by 2.5 hours, while the person with diabetes' blood glucose remains elevated above 160 mg/dL at 3 hours [1]
Marking note: Award 1 mark for each valid comparison. Must include reference to the data (values/times). Accept comparisons of the rate of decrease or the overall pattern.
(b) Explain the role of insulin and glucagon in regulating blood glucose concentration in a healthy person. [3]
Answer:
- When blood glucose concentration is high (e.g., after a meal), the pancreas releases insulin [1]
- Insulin stimulates the liver and muscle cells to convert glucose to glycogen, lowering blood glucose concentration [1]
- When blood glucose concentration is low (e.g., between meals), the pancreas releases glucagon, which stimulates the liver to convert glycogen back to glucose, raising blood glucose concentration [1]
Marking note: Award 1 mark for insulin release and its effect, 1 mark for glucagon release and its effect, and 1 mark for linking both to the maintenance of a relatively constant blood glucose concentration (negative feedback).
(c) Suggest why the blood glucose concentration of the person with diabetes remains elevated for a longer period. [2]
Answer:
- The person with diabetes does not produce enough insulin / their cells are resistant to insulin [1]
- Therefore, glucose is not converted to glycogen efficiently / cells do not take up glucose effectively, so blood glucose remains high [1]
Marking note: Award 1 mark for identifying the problem with insulin (deficiency or resistance), and 1 mark for explaining the consequence on glucose uptake or conversion. Accept reference to Type 1 or Type 2 diabetes.
14. Describe the process of gas exchange in the alveoli of the lungs. Explain how the structure of the alveoli is adapted for efficient gas exchange. [4]
Answer: Process:
- Oxygen diffuses from the alveoli into the blood capillaries, and carbon dioxide diffuses from the blood capillaries into the alveoli [1]
- This occurs down a concentration gradient [1]
Adaptations:
- The alveoli have a large surface area to volume ratio for faster diffusion [1]
- The walls of the alveoli and capillaries are one cell thick, providing a short diffusion distance [1]
- The alveoli are richly supplied with blood capillaries to maintain a steep concentration gradient [1]
- The surface of the alveoli is moist, allowing gases to dissolve before diffusing [1]
Marking note: Award up to 4 marks total. At least 1 mark must be for describing the process (diffusion of oxygen and carbon dioxide). The remaining marks are for adaptations. Accept any four valid points from the list above or other relevant adaptations (e.g., thin film of moisture).
15. Explain how the structure of an artery is related to its function of transporting blood away from the heart. [4]
Answer:
- Arteries have a thick muscular wall to withstand and maintain the high pressure of blood pumped from the heart [1]
- The wall contains elastic fibres that allow the artery to stretch and recoil, helping to push blood along and maintain pressure [1]
- The lumen is relatively narrow compared to veins, which helps to maintain high pressure [1]
- The smooth endothelial lining reduces friction, allowing blood to flow easily [1]
Marking note: Award 1 mark for each valid structural feature linked to its function. Accept reference to the absence of valves (except in the pulmonary artery and aorta) as blood is under high pressure and does not flow backwards.
Section D: Data-Based and Application Questions (5 marks)
16. Respiration in yeast experiment.
(a) Describe the trend shown by the results. [2]
Answer:
- As temperature increases from 10°C to 30°C, the volume of CO₂ produced increases [1]
- Above 30°C, the volume of CO₂ produced decreases [1]
Marking note: Award 1 mark for describing the increase up to 30°C, and 1 mark for describing the decrease above 30°C. Must reference the data (temperatures).
(b) Explain why the volume of carbon dioxide produced decreases at temperatures above 30°C. [2]
Answer:
- At high temperatures, the enzymes involved in respiration are denatured [1]
- The active site of the enzyme changes shape, so the substrate can no longer bind, and the rate of respiration decreases [1]
Marking note: Award 1 mark for stating that enzymes are denatured, and 1 mark for explaining the consequence (active site changes shape, enzyme-substrate complex cannot form, rate of reaction decreases).
17. Nephron structure and function.
(a) Name the process that occurs at the glomerulus. [1]
Answer: Ultrafiltration / Filtration
Marking note: Accept "ultrafiltration" or "filtration". Do not accept "selective reabsorption" (occurs later in the nephron).
(b) Explain why glucose is not normally found in the urine of a healthy person. [2]
Answer:
- Glucose is filtered out of the blood at the glomerulus, but is completely reabsorbed in the proximal convoluted tubule [1]
- This reabsorption occurs by active transport, so no glucose remains in the filtrate to be excreted [1]
Marking note: Award 1 mark for stating that glucose is reabsorbed, and 1 mark for stating where (proximal convoluted tubule) or how (active transport). Accept reference to the fact that all glucose is reabsorbed unless blood glucose concentration exceeds the renal threshold.
18. Alveoli condition.
(a) Explain how this condition would affect the person's ability to take in oxygen. [2]
Answer:
- The thickened alveolar wall increases the diffusion distance for oxygen [1]
- The reduced elasticity makes it harder for the alveoli to inflate and deflate, reducing the efficiency of ventilation / the volume of air exchanged [1]
Marking note: Award 1 mark for linking thickened walls to increased diffusion distance, and 1 mark for linking reduced elasticity to impaired ventilation. Accept reference to reduced surface area if implied.
(b) Suggest one symptom this person might experience and explain why. [1]
Answer:
- Shortness of breath / fatigue [1]
- Because less oxygen is taken into the blood, so less aerobic respiration can occur, producing less energy [1]
Marking note: Award 1 mark for a valid symptom and a valid explanation. Accept other relevant symptoms (e.g., rapid breathing, tiredness) with appropriate explanation.
19. The hormone adrenaline is released during times of stress or excitement. Describe the effects of adrenaline on the body and explain how these effects prepare the body for 'fight or flight'. [3]
Answer:
- Adrenaline increases heart rate and breathing rate, delivering more oxygen and glucose to muscles for respiration [1]
- It stimulates the liver to convert glycogen to glucose, increasing blood glucose concentration for energy [1]
- It causes pupils to dilate and diverts blood flow from non-essential organs (e.g., digestive system) to muscles, preparing the body for physical action [1]
Marking note: Award 1 mark for each valid effect linked to the 'fight or flight' response. Accept other effects such as increased sweating, hair standing on end, or mental alertness. The explanation must link the effect to preparing the body for action.
20. Explain the importance of maintaining a constant internal environment (homeostasis) in the human body. Use the regulation of body temperature as an example in your answer. [3]
Answer:
- Homeostasis ensures that enzymes work at their optimum conditions, maintaining metabolic reactions at a constant rate [1]
- For example, body temperature is maintained at around 37°C, which is the optimum temperature for human enzymes [1]
- If body temperature rises too high, enzymes may denature; if it falls too low, enzyme activity slows down, both of which can disrupt metabolism [1]
Marking note: Award 1 mark for linking homeostasis to enzyme function, 1 mark for using body temperature as an example with the correct optimum, and 1 mark for explaining the consequences of deviation from the optimum. Accept other valid examples of homeostasis (e.g., blood glucose, water balance) if used to support the explanation.
END OF ANSWER KEY