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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: ______ / 40
Duration: 45 minutes Total Marks: 40 Instructions: Answer ALL questions in the spaces provided. The marks for each question are indicated in brackets. Read each question carefully before answering.
Section A: Multiple Choice (5 marks)
Circle the correct answer for each question.
1. Which blood component is primarily responsible for transporting oxygen? A) Plasma B) White blood cells C) Red blood cells D) Platelets [1]
2. The hepatic portal vein transports blood from the: A) Heart to the liver B) Liver to the heart C) Intestines to the liver D) Liver to the intestines [1]
3. Which of the following correctly describes the role of the coronary arteries? A) Carry deoxygenated blood away from the heart B) Supply oxygenated blood to the heart muscle C) Return blood from the lungs to the heart D) Transport blood from the heart to the lungs [1]
4. During inhalation, which of the following occurs? A) Diaphragm relaxes and moves upwards B) Rib cage moves downwards and inwards C) Diaphragm contracts and flattens D) Volume of thoracic cavity decreases [1]
5. Which statement about enzymes in digestion is correct? A) Amylase breaks down proteins in the stomach B) Lipase breaks down fats in the mouth C) Protease breaks down proteins in the stomach D) Maltase breaks down starch in the small intestine [1]
Section B: Short Answer (15 marks)
Answer all questions in the spaces provided.
6. State TWO functions of the liver. [2]
7. Explain why the wall of the left ventricle is thicker than the wall of the right ventricle. [2]
8. A student measured their pulse rate before and after running for 5 minutes.
| Condition | Pulse rate (beats per minute) |
|---|---|
| At rest | 72 |
| After running | 118 |
Explain why the pulse rate increased after running. [2]
9. State ONE structural adaptation of a capillary and explain how this adaptation helps it perform its function. [2]
10. Define the term peristalsis and state where it occurs in the digestive system. [2]
11. Explain why a person with kidney failure may need to undergo dialysis. [2]
12. State the equation for aerobic respiration. [1]
13. Explain why breathing rate remains elevated for some time after vigorous exercise has stopped. [2]
Section C: Structured Response (20 marks)
Answer all questions in the spaces provided.
14. The diagram below shows a villus from the small intestine.
![Villus diagram - a finger-like projection with a network of blood capillaries and a central lacteal]
(a) Identify structure X (the central vessel). [1]
(b) Explain how the structure of a villus is adapted for efficient absorption of digested food. [3]
(c) Glucose is absorbed into the blood capillaries of the villus. Name the process by which glucose is absorbed when its concentration in the small intestine is lower than in the blood. [1]
15. The graph below shows the effect of temperature on the activity of a digestive enzyme.
![Graph showing enzyme activity increasing from 10°C to 37°C, peaking at 37°C, then decreasing sharply from 40°C to 60°C]
(a) Describe the trend shown in the graph between 10°C and 37°C. [1]
(b) Explain why enzyme activity increases as temperature rises from 10°C to 37°C. [2]
(c) Explain why enzyme activity decreases sharply above 40°C. [2]
(d) Predict what would happen to enzyme activity at 70°C. Explain your answer. [2]
16. The table below shows the composition of blood plasma, glomerular filtrate, and urine in a healthy person.
| Substance | Blood plasma (g/100cm³) | Glomerular filtrate (g/100cm³) | Urine (g/100cm³) |
|---|---|---|---|
| Protein | 7.0 | 0.0 | 0.0 |
| Glucose | 0.1 | 0.1 | 0.0 |
| Urea | 0.03 | 0.03 | 2.0 |
| Water | 90.0 | 90.0 | 96.0 |
(a) Explain why protein is present in blood plasma but absent from glomerular filtrate. [2]
(b) Explain why glucose is present in glomerular filtrate but absent from urine. [2]
(c) Explain why the concentration of urea is much higher in urine than in glomerular filtrate. [2]
17. Describe the pathway of blood through the heart, starting from the vena cava and ending at the aorta. Include the names of all chambers and valves the blood passes through. [4]
18. Explain how the structure of an alveolus is adapted for efficient gas exchange. [3]
19. A person accidentally touches a hot object and immediately withdraws their hand.
(a) Name the type of response described above. [1]
(b) Outline the pathway of the nerve impulse in this response, from the receptor to the effector. [3]
20. Explain how insulin and glucagon work together to regulate blood glucose concentration. [4]
END OF QUIZ
Answers
Secondary 3 Biology Quiz - Human Physiology - ANSWER KEY
Total Marks: 40
Section A: Multiple Choice (5 marks)
| Question | Answer | Marking Notes |
|---|---|---|
| 1 | C | Red blood cells contain haemoglobin which binds to oxygen for transport. |
| 2 | C | The hepatic portal vein carries nutrient-rich blood from the intestines to the liver for processing. |
| 3 | B | Coronary arteries branch from the aorta and supply oxygenated blood to the heart muscle itself. |
| 4 | C | During inhalation, the diaphragm contracts and flattens, increasing thoracic volume and drawing air in. |
| 5 | C | Protease (pepsin) breaks down proteins in the stomach. Amylase acts on starch, lipase on fats, maltase on maltose. |
Section B: Short Answer (15 marks)
6. State TWO functions of the liver. [2]
Answer: Any two of the following (1 mark each):
- Regulation of blood glucose concentration (converts excess glucose to glycogen / converts glycogen to glucose)
- Breakdown of excess amino acids (deamination) / formation of urea
- Breakdown of alcohol / detoxification
- Production of bile (for fat digestion/emulsification)
- Storage of iron / vitamins
- Breakdown of old red blood cells
7. Explain why the wall of the left ventricle is thicker than the wall of the right ventricle. [2]
Answer:
- The left ventricle pumps blood to the entire body (systemic circulation) [1]
- Therefore, it needs to generate higher pressure to overcome greater resistance / pump blood a longer distance [1]
- (Accept: The right ventricle only pumps blood to the lungs (pulmonary circulation), which is a shorter distance and requires less pressure.)
8. Explain why the pulse rate increased after running. [2]
Answer:
- During running, muscles require more energy / carry out more respiration [1]
- Therefore, the heart beats faster to deliver more oxygen and glucose to muscles / remove carbon dioxide and lactic acid more quickly [1]
9. State ONE structural adaptation of a capillary and explain how this adaptation helps it perform its function. [2]
Answer:
- Adaptation: Capillary walls are one-cell thick / thin walls [1]
- Explanation: This provides a short diffusion distance for efficient exchange of substances (oxygen, carbon dioxide, nutrients, waste) between blood and tissue fluid [1]
- (Accept: Capillaries are narrow / have a small diameter — this slows blood flow, allowing more time for exchange / brings blood close to cells.)
10. Define the term peristalsis and state where it occurs in the digestive system. [2]
Answer:
- Definition: Peristalsis is the rhythmic, wave-like contraction and relaxation of muscles in the wall of the alimentary canal that pushes food along [1]
- Location: It occurs along the oesophagus / stomach / small intestine / large intestine (any correct part of the alimentary canal) [1]
11. Explain why a person with kidney failure may need to undergo dialysis. [2]
Answer:
- In kidney failure, the kidneys cannot effectively filter blood / remove metabolic waste products such as urea [1]
- Dialysis uses a machine with a semi-permeable membrane to remove urea and excess water/salts from the blood, performing the function of the failed kidneys [1]
12. State the equation for aerobic respiration. [1]
Answer:
- C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)
- (Accept word equation: glucose + oxygen → carbon dioxide + water + energy)
13. Explain why breathing rate remains elevated for some time after vigorous exercise has stopped. [2]
Answer:
- During vigorous exercise, anaerobic respiration occurs in muscles, producing lactic acid [1]
- After exercise, extra oxygen is needed to break down/oxidise the accumulated lactic acid (repaying the oxygen debt), so breathing rate remains elevated to take in more oxygen [1]
Section C: Structured Response (20 marks)
14. Villus structure and absorption
(a) Identify structure X (the central vessel). [1]
Answer: Lacteal / lymph vessel / lymphatic vessel
(b) Explain how the structure of a villus is adapted for efficient absorption of digested food. [3]
Answer (any three adaptations with explanations, 1 mark each):
- Finger-like projection: increases surface area for absorption
- Thin epithelium / one-cell thick wall: provides a short diffusion distance for absorbed nutrients
- Dense network of blood capillaries: rapidly transports absorbed glucose and amino acids away, maintaining a concentration gradient
- Lacteal present: absorbs and transports fats/fatty acids and glycerol
- Microvilli on epithelial cells: further increase surface area for absorption
(c) Name the process by which glucose is absorbed when its concentration in the small intestine is lower than in the blood. [1]
Answer: Active transport
15. Enzyme activity and temperature
(a) Describe the trend shown in the graph between 10°C and 37°C. [1]
Answer: As temperature increases from 10°C to 37°C, enzyme activity increases.
(b) Explain why enzyme activity increases as temperature rises from 10°C to 37°C. [2]
Answer:
- As temperature increases, the kinetic energy of enzyme and substrate molecules increases [1]
- This leads to more frequent and more energetic collisions between enzyme and substrate molecules, increasing the rate of enzyme-substrate complex formation / increasing the rate of reaction [1]
(c) Explain why enzyme activity decreases sharply above 40°C. [2]
Answer:
- Above 40°C, the high temperature causes the enzyme to denature [1]
- The shape of the active site is altered/changed, so the substrate can no longer fit/bind to the active site (lock-and-key model disrupted) [1]
(d) Predict what would happen to enzyme activity at 70°C. Explain your answer. [2]
Answer:
- Prediction: Enzyme activity would be zero / the enzyme would be completely denatured / no reaction would occur [1]
- Explanation: At 70°C, the enzyme is fully denatured; the active site is permanently destroyed and cannot be restored, so no enzyme-substrate complexes can form [1]
16. Kidney function and urine formation
(a) Explain why protein is present in blood plasma but absent from glomerular filtrate. [2]
Answer:
- During ultrafiltration in the glomerulus, blood is filtered under high pressure through the basement membrane / filtration slits [1]
- Protein molecules are too large to pass through the filtration membrane, so they remain in the blood and are not filtered into the Bowman's capsule [1]
(b) Explain why glucose is present in glomerular filtrate but absent from urine. [2]
Answer:
- Glucose molecules are small enough to pass through the filtration membrane during ultrafiltration, so they enter the glomerular filtrate [1]
- However, all glucose is selectively reabsorbed back into the blood in the proximal convoluted tubule, so no glucose appears in the urine of a healthy person [1]
(c) Explain why the concentration of urea is much higher in urine than in glomerular filtrate. [2]
Answer:
- As filtrate moves through the nephron, most of the water is reabsorbed back into the blood [1]
- Urea is not reabsorbed (or only a small amount is reabsorbed), so it becomes more concentrated as water is removed, resulting in a higher concentration in urine [1]
17. Pathway of blood through the heart [4]
Answer: Blood flows through the heart in the following sequence (1 mark for each correct segment, up to 4 marks):
- Deoxygenated blood enters the right atrium from the vena cava
- Blood passes through the tricuspid valve into the right ventricle
- Right ventricle contracts; blood passes through the semilunar/pulmonary valve into the pulmonary artery → to lungs
- Oxygenated blood returns from lungs via pulmonary veins into the left atrium
- Blood passes through the bicuspid/mitral valve into the left ventricle
- Left ventricle contracts; blood passes through the aortic/semilunar valve into the aorta → to body
(Award marks for correct sequence including: right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary artery → lungs → pulmonary veins → left atrium → bicuspid valve → left ventricle → aortic valve → aorta. Accept 4 correct sequential steps for full marks.)
18. Alveolus structure and gas exchange [3]
Answer (any three adaptations with explanations, 1 mark each):
- Thin walls / one-cell thick epithelium: provides a short diffusion distance for oxygen and carbon dioxide
- Large surface area (numerous alveoli): maximises the area available for gas exchange
- Moist inner surface: allows gases to dissolve before diffusing across the membrane
- Dense network of blood capillaries surrounding each alveolus: maintains a steep concentration gradient by rapidly transporting gases to and from the alveoli
- Elastic walls: allow alveoli to expand and recoil during breathing, maintaining airflow
19. Reflex action
(a) Name the type of response described. [1]
Answer: Reflex action / reflex arc / reflex response
(b) Outline the pathway of the nerve impulse in this response, from the receptor to the effector. [3]
Answer:
- Receptor (in skin) detects the stimulus (heat) and generates a nerve impulse [1]
- Sensory neurone transmits the impulse to the spinal cord / central nervous system [1]
- In the spinal cord, the impulse passes across a synapse to a relay neurone, then to a motor neurone
- Motor neurone transmits the impulse to the effector (muscle in the arm) [1]
- The effector (biceps muscle) contracts, causing the hand to withdraw
(Award marks for correct sequence: receptor → sensory neurone → relay neurone (in spinal cord) → motor neurone → effector. Accept 3 correct sequential steps.)
20. Blood glucose regulation [4]
Answer:
-
When blood glucose concentration is too high (e.g., after a meal):
- The pancreas detects the increase and releases insulin [1]
- Insulin stimulates the liver (and muscle cells) to convert excess glucose into glycogen for storage [1]
- This lowers blood glucose concentration back to normal
-
When blood glucose concentration is too low (e.g., during fasting/exercise):
- The pancreas detects the decrease and releases glucagon [1]
- Glucagon stimulates the liver to convert stored glycogen back into glucose, which is released into the blood [1]
- This raises blood glucose concentration back to normal
-
This is an example of negative feedback, maintaining blood glucose within a narrow range (homeostasis).
(Award marks for: insulin role [1], glycogen conversion/storage [1], glucagon role [1], glycogen breakdown/glucose release [1]. Accept reference to negative feedback as an additional valid point.)
END OF ANSWER KEY