O Level Biology Human Physiology Quiz

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O-Level Biology Quiz - Human Physiology

Name: ________________________
Class: ________________________
Date: ________________________
Score: ______ / 50

Duration: 45 minutes
Total Marks: 50

Instructions:

• This quiz contains 20 questions on Human Physiology.
• Answer ALL questions in the spaces provided.
• The number of marks is given in brackets [ ] at the end of each question or part question.
• Show your reasoning where appropriate.

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Section A: Short Answer (15 marks)

Answer all questions in this section.

1. State the equation for aerobic respiration in humans. [1]

2. Name the blood vessel that carries deoxygenated blood from the heart to the lungs. [1]

3. Define the term excretion. [1]

4. State one function of the liver in metabolism. [1]

5. Name the hormone that stimulates the conversion of glycogen to glucose in the liver. [1]

6. Identify the type of neurone that transmits an impulse from a receptor to the central nervous system. [1]

7. State the function of platelets in the blood. [1]

8. Name the structure in the nephron where ultrafiltration occurs. [1]

9. State one structural difference between an artery and a vein. [1]

10. Name the enzyme present in saliva that begins the digestion of starch. [1]

11. State the function of the coronary arteries. [1]

12. Identify the hormone produced by the islets of Langerhans that lowers blood glucose concentration. [1]

13. Name the process by which water is reabsorbed from the glomerular filtrate back into the blood in the nephron. [1]

14. State the function of the bicuspid (mitral) valve in the heart. [1]

15. Name the gas that is the main waste product of aerobic respiration. [1]

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Section B: Structured Questions (20 marks)

Answer all questions in this section.

16. The diagram below represents part of the human respiratory system.

(a) Name the structures labelled A and B. [2]

A: ________________________

B: ________________________

(b) Explain two ways in which the structure of an alveolus is adapted for efficient gas exchange. [4]

Adaptation 1: ____________________________________________________________

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Adaptation 2: ____________________________________________________________

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(c) Describe the mechanism of breathing during inhalation (breathing in). [3]

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17. A student investigated the effect of exercise on heart rate. The results are shown in the table below.

Time (min)	Heart rate (beats per min)
0 (rest)	72
2	95
4	118
6	130
8	125
10	110
12	88
14	76

(a) Describe the trend in heart rate from 0 to 6 minutes. [1]

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(b) Explain why the heart rate increases during exercise. [3]

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(c) Explain why the heart rate does not return to the resting level immediately after exercise stops. [2]

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18. The diagram below shows a reflex arc.

(a) State what is meant by a reflex action. [1]

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(b) Describe the pathway of a nerve impulse in a reflex arc, naming the types of neurones involved. [4]

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Section C: Data-Based and Extended Response (15 marks)

Answer all questions in this section.

19. A person consumes a meal rich in carbohydrates. The graph below shows the changes in blood glucose concentration over the next three hours.

(a) Describe the changes in blood glucose concentration shown in the graph. [2]

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(b) Explain the role of insulin and glucagon in regulating blood glucose concentration after the meal. [5]

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20. Describe the process of double circulation in humans. In your answer, name the chambers of the heart and the main blood vessels involved, and explain the importance of having a double circulatory system. [8]

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END OF QUIZ

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O-Level Biology Quiz - Human Physiology — Answer Key and Marking Scheme

Total Marks: 50

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Section A: Short Answer (15 × 1 mark = 15 marks)

Q	Answer	Marking Notes
1	Glucose + Oxygen → Carbon dioxide + Water (+ Energy) / C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ Energy)	Accept word or symbol equation. Must include all reactants and products. Energy/ATP is optional. [1]
2	Pulmonary artery	Accept "pulmonary artery". Do not accept "pulmonary vein". [1]
3	Excretion is the removal of metabolic waste products (from the body) / removal of waste products produced by chemical reactions in cells	Must include "metabolic" or equivalent (e.g., "produced by the body's chemical reactions"). Do not accept "removal of faeces" (egestion). [1]
4	Any one of: (i) conversion of excess glucose to glycogen for storage; (ii) conversion of glycogen to glucose when needed; (iii) deamination of excess amino acids / formation of urea; (iv) production of bile; (v) breakdown of hormones/alcohol/drugs (detoxification)	Accept any one valid metabolic function. [1]
5	Glucagon	Must be "glucagon". Do not accept "insulin". [1]
6	Sensory neurone	Accept "sensory neurone" or "afferent neurone". [1]
7	Blood clotting / involved in the conversion of fibrinogen to fibrin (to form a clot)	Accept "clotting" or description of the clotting process. [1]
8	Glomerulus / Bowman's capsule	Accept either "glomerulus" or "Bowman's capsule". [1]
9	Any one of: (i) artery has thicker wall / vein has thinner wall; (ii) artery has narrower lumen / vein has wider lumen; (iii) artery has more elastic and muscular tissue / vein has less; (iv) veins have valves / arteries do not (except semilunar valves at base of pulmonary artery and aorta)	Accept any one valid structural difference. Must be comparative. [1]
10	Salivary amylase / amylase	Accept "salivary amylase" or "amylase". [1]
11	Supply the heart muscle (cardiac muscle) with oxygenated blood / oxygen and nutrients	Must mention "heart muscle" or "cardiac muscle". [1]
12	Insulin	Must be "insulin". [1]
13	Osmosis / selective reabsorption (by osmosis)	Accept "osmosis" or "selective reabsorption". [1]
14	Prevents backflow of blood from the left ventricle to the left atrium / ensures one-way flow of blood from left atrium to left ventricle	Must mention "prevents backflow" or "one-way flow" and identify the correct chambers. [1]
15	Carbon dioxide / CO₂	Accept "carbon dioxide" or "CO₂". [1]

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Section B: Structured Questions (20 marks)

Question 16 (9 marks)

(a) [2 marks]

• A: Trachea / windpipe [1]
• B: Bronchus / bronchi [1]

(b) [4 marks] Award up to 2 marks for each adaptation with explanation (2 × 2 marks):

• Adaptation 1: Alveolar wall is one cell thick (squamous epithelium) [1] → provides a short diffusion distance for gases / faster diffusion [1].
• Adaptation 2: Alveoli are surrounded by a dense network of blood capillaries [1] → maintains a steep concentration gradient for oxygen and carbon dioxide / continuous blood flow removes oxygen and brings carbon dioxide [1].
• Alternative adaptations: (i) Large number of alveoli → large total surface area for gas exchange. (ii) Moist inner surface → allows oxygen to dissolve before diffusing across. (iii) Thin film of moisture → facilitates diffusion of gases.

(c) [3 marks]

• The diaphragm contracts and flattens [1].
• The external intercostal muscles contract, moving the rib cage upwards and outwards [1].
• These actions increase the volume of the thoracic cavity, decreasing the pressure inside the lungs below atmospheric pressure, so air rushes in [1].

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Question 17 (6 marks)

(a) [1 mark]

• The heart rate increases (steadily) from 72 bpm at rest to 130 bpm at 6 minutes. [1]

(b) [3 marks]

• During exercise, muscles contract more frequently and require more energy (ATP) [1].
• More aerobic respiration occurs, requiring more oxygen and producing more carbon dioxide [1].
• The heart rate increases to pump blood faster, delivering more oxygen to the muscles and removing carbon dioxide more quickly [1].

(c) [2 marks]

• After exercise, an oxygen debt remains because anaerobic respiration has produced lactic acid in the muscles [1].
• The heart rate remains elevated to continue delivering oxygen to the muscles to oxidise/break down the lactic acid (repay the oxygen debt) [1].

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Question 18 (5 marks)

(a) [1 mark]

• A reflex action is an automatic/rapid/involuntary response to a stimulus, without conscious thought / that does not involve the brain. [1]

(b) [4 marks]

• The stimulus is detected by a receptor, which generates a nerve impulse [1].
• The impulse travels along a sensory neurone to the spinal cord (central nervous system) [1].
• In the spinal cord, the impulse is transmitted across a synapse to a relay neurone (intermediate neurone) [1].
• The relay neurone transmits the impulse across another synapse to a motor neurone, which carries the impulse to an effector (muscle or gland), producing the response [1].

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Section C: Data-Based and Extended Response (15 marks)

Question 19 (7 marks)

(a) [2 marks]

• Blood glucose concentration rises sharply after the meal, reaching a peak (at approximately 30–60 minutes) [1].
• It then decreases gradually, returning to near the normal/fasting level by about 2–3 hours [1].

(b) [5 marks]

• After a carbohydrate-rich meal, glucose is absorbed from the small intestine into the blood, causing blood glucose concentration to rise [1].
• The rise in blood glucose is detected by the islets of Langerhans in the pancreas, which secrete insulin into the blood [1].
• Insulin stimulates the liver (and muscle cells) to convert excess glucose into glycogen for storage, and increases glucose uptake by cells, lowering blood glucose concentration back to normal [1].
• As blood glucose concentration falls below the normal level, the pancreas detects this and secretes glucagon [1].
• Glucagon stimulates the liver to convert stored glycogen back into glucose and release it into the blood, raising blood glucose concentration back to normal. This is an example of negative feedback [1].

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Question 20 (8 marks)

Marking scheme for double circulation description:

Mark	Description
1	Pulmonary circulation: Deoxygenated blood from the body enters the right atrium via the vena cavae.
2	Blood passes to the right ventricle, which pumps it to the lungs via the pulmonary artery.
3	In the lungs, gas exchange occurs: blood releases carbon dioxide and picks up oxygen (becomes oxygenated).
4	Oxygenated blood returns to the left atrium via the pulmonary vein.
5	Systemic circulation: Blood passes from the left atrium to the left ventricle, which pumps it to the body (except lungs) via the aorta.
6	Oxygen and nutrients are delivered to body cells; carbon dioxide and waste products are collected. Deoxygenated blood returns to the right atrium via the vena cavae.
7	Importance: The double circulatory system separates oxygenated and deoxygenated blood, ensuring that oxygen-rich blood is delivered to the body at high pressure.
8	This allows efficient delivery of oxygen to respiring tissues, supporting the high metabolic rate of mammals/humans.

Award marks for correct naming of chambers (right atrium, right ventricle, left atrium, left ventricle) and vessels (vena cava, pulmonary artery, pulmonary vein, aorta), correct sequence, and explanation of importance.

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END OF ANSWER KEY