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Secondary 4 Pure Biology Human Physiology Quiz
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Questions
Secondary 4 Pure Biology Quiz – Human Physiology
Name: ________________________
Class: ________________________
Date: ________________________
Score: ______ / 50
Duration: 45 minutes
Total Marks: 50
Instructions: Answer ALL questions in the spaces provided. Marks are indicated in brackets [ ]. Show your working for calculation questions. Diagrams may be drawn in pencil.
Section A: Short Answer (10 marks)
Answer all questions in this section.
1. State the function of the hepatic portal vein. [1 mark]
2. Name the blood vessel that carries oxygenated blood from the lungs to the heart. [1 mark]
3. State one structural difference between an artery and a vein. [1 mark]
4. Define excretion. [1 mark]
5. Name the hormone that stimulates the conversion of glycogen to glucose in the liver. [1 mark]
6. State the role of platelets in the blood. [1 mark]
7. Name the structure in the nephron where ultrafiltration occurs. [1 mark]
8. State one function of the liver other than glucose regulation. [1 mark]
9. Name the type of neurone that carries impulses from the central nervous system to an effector. [1 mark]
10. State the function of the cornea in the eye. [1 mark]
Section B: Structured Questions (24 marks)
Answer all questions in this section.
11. Fig. 1.1 shows pressure changes in the left ventricle and the aorta during one cardiac cycle.
| Time (s) | Left ventricular pressure (mmHg) | Aortic pressure (mmHg) |
|---|---|---|
| 0.0 | 5 | 80 |
| 0.1 | 20 | 80 |
| 0.2 | 80 | 80 |
| 0.3 | 120 | 120 |
| 0.4 | 60 | 100 |
| 0.5 | 5 | 80 |
(a) State the time at which the semilunar valves open. Explain your answer. [2 marks]
(b) Explain what causes the left ventricular pressure to decrease between 0.3 s and 0.5 s. [2 marks]
(c) Predict how the pressure values would differ if they were recorded from the right ventricle. Explain your answer. [2 marks]
12. A patient with kidney failure undergoes haemodialysis. The dialysis fluid (dialysate) contains 0 g/dm³ of urea, while the patient's blood plasma contains 0.3 g/dm³ of urea before dialysis. After 4 hours of dialysis, the blood urea concentration is 0.1 g/dm³. The patient has 5 dm³ of blood.
(a) Calculate the total mass of urea removed from the patient's blood during the 4-hour dialysis session. Show your working. [2 marks]
(b) Calculate the average hourly rate of urea removal in g/hour. Show your working. [1 mark]
(c) Explain why the dialysis fluid contains no urea but has glucose and mineral ions at concentrations similar to those in healthy blood plasma. [3 marks]
13. Fig. 1.2 shows a reflex arc involved in withdrawing the hand from a hot object.
(a) Name the three types of neurones involved in this reflex arc, in the correct order. [3 marks]
(b) Explain why a reflex action is faster than a voluntary action. [2 marks]
(c) Explain the importance of reflex actions in protecting the body. [2 marks]
14. A student investigated the effect of different concentrations of sucrose solution on red blood cells. The results are shown in Table 1.1.
| Sucrose concentration (mol/dm³) | Appearance of red blood cells |
|---|---|
| 0.0 (distilled water) | Swollen, some burst |
| 0.15 | Normal |
| 0.30 | Shrivelled (crenated) |
(a) Explain why the red blood cells burst in distilled water. [2 marks]
(b) Explain why the red blood cells became shrivelled in 0.30 mol/dm³ sucrose solution. [2 marks]
(c) State what the results suggest about the water potential of red blood cells relative to a 0.15 mol/dm³ sucrose solution. [1 mark]
Section C: Data-Based and Extended Response (16 marks)
Answer all questions in this section.
15. Fig. 1.3 shows the changes in blood glucose concentration of a healthy person and a person with Type 1 diabetes after consuming a glucose drink at time 0.
| Time (hours) | Blood glucose – Healthy (mmol/dm³) | Blood glucose – Type 1 diabetic (mmol/dm³) |
|---|---|---|
| 0 | 5.0 | 10.0 |
| 0.5 | 7.5 | 14.0 |
| 1.0 | 8.5 | 17.0 |
| 1.5 | 7.0 | 17.5 |
| 2.0 | 5.5 | 17.0 |
| 2.5 | 5.0 | 16.5 |
(a) Describe the changes in blood glucose concentration in the healthy person between 0 and 2.5 hours. [2 marks]
(b) Explain the role of insulin and glucagon in producing the changes observed in the healthy person. [4 marks]
(c) Explain why the blood glucose concentration of the person with Type 1 diabetes remains high. [2 marks]
16. Fig. 1.4 is a diagram of the human respiratory system.
(a) Describe the pathway taken by an oxygen molecule from the atmosphere to the blood in the pulmonary capillaries. [3 marks]
(b) Explain three ways in which the structure of an alveolus is adapted for efficient gas exchange. [3 marks]
(c) Explain why the concentration of carbon dioxide in exhaled air is higher than in inhaled air. [2 marks]
17. Discuss the long-term effects of excessive alcohol consumption on the human body. In your answer, you should refer to at least two organ systems. [4 marks]
18. Explain how the body responds to a decrease in environmental temperature to maintain a constant core body temperature of approximately 37°C. [4 marks]
19. A person is blood group A. Explain why this person can receive blood from a group O donor but cannot receive blood from a group B donor. [2 marks]
20. Describe the process of peristalsis and explain its importance in the human digestive system. [2 marks]
END OF QUIZ
Answers
Secondary 4 Pure Biology Quiz – Human Physiology
ANSWER KEY AND MARKING SCHEME
Total Marks: 50
Section A: Short Answer (10 marks)
1. State the function of the hepatic portal vein. [1 mark]
Answer: It transports blood rich in absorbed nutrients (e.g., glucose, amino acids) from the small intestine (ileum) directly to the liver for processing / before the blood enters general circulation.
Marking note: Accept "carries blood from the gut to the liver" or "transports absorbed food substances to the liver."
2. Name the blood vessel that carries oxygenated blood from the lungs to the heart. [1 mark]
Answer: Pulmonary vein.
Marking note: Must specify "pulmonary vein." "Vein" alone is insufficient.
3. State one structural difference between an artery and a vein. [1 mark]
Answer: Arteries have thicker muscular/elastic walls than veins. / Veins have valves; arteries do not (except semilunar valves at the base of the pulmonary artery and aorta). / Arteries have a narrower lumen relative to wall thickness.
Marking note: Accept any one valid structural difference.
4. Define excretion. [1 mark]
Answer: Excretion is the removal of metabolic waste products (e.g., urea, carbon dioxide) / toxic substances produced by chemical reactions in the body.
Marking note: Must mention "metabolic waste" or "waste products of metabolism." Egestion (removal of faeces) is not accepted.
5. Name the hormone that stimulates the conversion of glycogen to glucose in the liver. [1 mark]
Answer: Glucagon.
Marking note: "Insulin" is incorrect (insulin stimulates glucose to glycogen conversion).
6. State the role of platelets in the blood. [1 mark]
Answer: Platelets are involved in blood clotting / they help to form a clot to prevent blood loss and entry of pathogens at a wound site.
Marking note: Accept "blood clotting" or "clot formation."
7. Name the structure in the nephron where ultrafiltration occurs. [1 mark]
Answer: Bowman's capsule / renal capsule / glomerulus (and Bowman's capsule).
Marking note: Accept "glomerulus" or "Bowman's capsule" or "renal corpuscle."
8. State one function of the liver other than glucose regulation. [1 mark]
Answer: Any one of: breakdown of excess amino acids (deamination) / production of bile / breakdown of alcohol / storage of vitamins and minerals / synthesis of plasma proteins / breakdown of old red blood cells.
Marking note: Accept any valid liver function other than glycogen/glucose regulation.
9. Name the type of neurone that carries impulses from the central nervous system to an effector. [1 mark]
Answer: Motor neurone / efferent neurone.
Marking note: "Sensory neurone" or "relay neurone" is incorrect.
10. State the function of the cornea in the eye. [1 mark]
Answer: The cornea refracts (bends) light rays entering the eye / it is the main structure responsible for focusing light onto the retina.
Marking note: Accept "refracts light" or "helps focus light."
Section B: Structured Questions (24 marks)
11. Cardiac cycle data interpretation.
(a) State the time at which the semilunar valves open. Explain your answer. [2 marks]
Answer: At 0.2–0.3 s. The semilunar valves open when the left ventricular pressure exceeds the aortic pressure. At 0.2 s, ventricular pressure (80 mmHg) equals aortic pressure (80 mmHg); by 0.3 s, ventricular pressure (120 mmHg) exceeds aortic pressure (120 mmHg), so the valves open between these times.
Marking: 1 mark for correct time (0.2–0.3 s or "between 0.2 and 0.3 s"); 1 mark for explanation linking ventricular pressure exceeding aortic pressure.
(b) Explain what causes the left ventricular pressure to decrease between 0.3 s and 0.5 s. [2 marks]
Answer: Ventricular diastole / relaxation of the ventricular muscles occurs. The ventricle relaxes, reducing pressure. Blood has been ejected into the aorta, so the volume of blood in the ventricle decreases, contributing to the pressure drop.
Marking: 1 mark for stating ventricular diastole/relaxation; 1 mark for linking relaxation and reduced blood volume to pressure decrease.
(c) Predict how the pressure values would differ if they were recorded from the right ventricle. Explain your answer. [2 marks]
Answer: The maximum pressure in the right ventricle would be much lower (approximately 25–30 mmHg). The right ventricle pumps blood only to the lungs (pulmonary circulation), which is a shorter circuit with lower resistance, so less pressure is needed compared to the left ventricle, which pumps blood to the entire body (systemic circulation).
Marking: 1 mark for stating pressure would be lower; 1 mark for explanation linking to pulmonary vs. systemic circulation resistance.
12. Kidney dialysis calculation.
(a) Calculate the total mass of urea removed from the patient's blood during the 4-hour dialysis session. Show your working. [2 marks]
Answer:
Initial urea concentration = 0.3 g/dm³
Final urea concentration = 0.1 g/dm³
Decrease in concentration = 0.3 – 0.1 = 0.2 g/dm³
Blood volume = 5 dm³
Total mass removed = 0.2 g/dm³ × 5 dm³ = 1.0 g
Marking: 1 mark for correct calculation of concentration decrease; 1 mark for correct final answer with units. Accept equivalent working.
(b) Calculate the average hourly rate of urea removal in g/hour. Show your working. [1 mark]
Answer:
Average hourly rate = Total mass removed ÷ Time = 1.0 g ÷ 4 h = 0.25 g/hour
Marking: 1 mark for correct answer with units.
(c) Explain why the dialysis fluid contains no urea but has glucose and mineral ions at concentrations similar to those in healthy blood plasma. [3 marks]
Answer:
- The dialysis fluid contains no urea to maintain a steep concentration gradient for urea between the blood and the dialysis fluid. This ensures urea diffuses out of the blood into the dialysis fluid down its concentration gradient.
- Glucose and mineral ions are at concentrations similar to healthy blood plasma to prevent their net movement out of the blood. If the dialysis fluid lacked these substances, they would diffuse out of the blood, causing deficiency. If they were at higher concentrations, they would diffuse into the blood, causing harmful accumulation.
Marking: 1 mark for urea explanation (concentration gradient, diffusion out of blood); 1 mark for glucose/minerals explanation (prevent loss); 1 mark for glucose/minerals explanation (prevent excess gain).
13. Reflex arc.
(a) Name the three types of neurones involved in this reflex arc, in the correct order. [3 marks]
Answer: Sensory neurone → Relay neurone (intermediate/interneurone) → Motor neurone.
Marking: 1 mark for each correct neurone type in the correct order.
(b) Explain why a reflex action is faster than a voluntary action. [2 marks]
Answer: A reflex action involves only the spinal cord (or brain stem) and does not require processing by the conscious brain (cerebrum). The impulse travels along a shorter pathway with fewer synapses, reducing the time taken for the response.
Marking: 1 mark for mentioning spinal cord/brain stem vs. conscious brain; 1 mark for shorter pathway/fewer synapses.
(c) Explain the importance of reflex actions in protecting the body. [2 marks]
Answer: Reflex actions produce rapid, automatic responses to harmful stimuli (e.g., heat, sharp objects), allowing the body to withdraw from danger before conscious awareness. This minimises tissue damage and prevents injury.
Marking: 1 mark for rapid/automatic response; 1 mark for minimising damage/preventing injury.
14. Osmosis and red blood cells.
(a) Explain why the red blood cells burst in distilled water. [2 marks]
Answer: Distilled water has a higher water potential than the cytoplasm of the red blood cells. Water enters the cells by osmosis, down the water potential gradient. The cells swell and eventually burst (haemolysis) because the cell membrane cannot withstand the increased internal pressure.
Marking: 1 mark for water entering by osmosis (water potential gradient); 1 mark for swelling and bursting.
(b) Explain why the red blood cells became shrivelled in 0.30 mol/dm³ sucrose solution. [2 marks]
Answer: The 0.30 mol/dm³ sucrose solution has a lower water potential than the red blood cell cytoplasm. Water leaves the cells by osmosis, down the water potential gradient. The cells lose water, shrink, and become crenated (shrivelled).
Marking: 1 mark for water leaving by osmosis; 1 mark for shrinkage/crenation.
(c) State what the results suggest about the water potential of red blood cells relative to a 0.15 mol/dm³ sucrose solution. [1 mark]
Answer: The water potential of the red blood cells is equal to / isotonic to the water potential of the 0.15 mol/dm³ sucrose solution (since the cells remained normal).
Marking: 1 mark for "equal" or "isotonic."
Section C: Data-Based and Extended Response (16 marks)
15. Blood glucose regulation.
(a) Describe the changes in blood glucose concentration in the healthy person between 0 and 2.5 hours. [2 marks]
Answer: Blood glucose concentration increases from 5.0 to a peak of 8.5 mmol/dm³ at 1.0 hour, then decreases to 5.0 mmol/dm³ by 2.5 hours, returning to the original level.
Marking: 1 mark for describing the increase to a peak; 1 mark for describing the decrease back to baseline.
(b) Explain the role of insulin and glucagon in producing the changes observed in the healthy person. [4 marks]
Answer:
- After consuming the glucose drink, blood glucose concentration rises. The pancreas detects this increase and secretes insulin. Insulin stimulates the liver and muscle cells to take up glucose and convert it to glycogen for storage. This reduces blood glucose concentration.
- As blood glucose concentration falls below normal, the pancreas secretes glucagon. Glucagon stimulates the liver to convert stored glycogen back to glucose, which is released into the blood, raising blood glucose concentration back to normal.
- This is an example of negative feedback, maintaining blood glucose within a narrow range.
Marking: 1 mark for insulin secretion in response to high glucose; 1 mark for insulin action (glucose to glycogen); 1 mark for glucagon secretion in response to low glucose; 1 mark for glucagon action (glycogen to glucose) / negative feedback.
(c) Explain why the blood glucose concentration of the person with Type 1 diabetes remains high. [2 marks]
Answer: Type 1 diabetes results from the destruction of insulin-producing cells in the pancreas, so little or no insulin is produced. Without insulin, cells cannot take up glucose from the blood, and the liver cannot convert excess glucose to glycogen. Therefore, blood glucose concentration remains high after consuming glucose.
Marking: 1 mark for lack of insulin production; 1 mark for consequence (cells cannot take up glucose / glycogen not formed).
16. Respiratory system.
(a) Describe the pathway taken by an oxygen molecule from the atmosphere to the blood in the pulmonary capillaries. [3 marks]
Answer: Oxygen enters through the nasal cavity / mouth → trachea → bronchi → bronchioles → alveoli (air sacs). From the alveoli, oxygen diffuses across the alveolar wall and the capillary wall into the blood in the pulmonary capillaries.
Marking: 1 mark for trachea and bronchi; 1 mark for bronchioles and alveoli; 1 mark for diffusion into capillaries.
(b) Explain three ways in which the structure of an alveolus is adapted for efficient gas exchange. [3 marks]
Answer:
- The alveolar wall is one cell thick (squamous epithelium), providing a short diffusion distance for gases.
- Alveoli are surrounded by a dense network of blood capillaries, maintaining a steep concentration gradient by constantly removing oxygen and bringing carbon dioxide.
- The alveoli provide a large total surface area (due to their large number and spherical shape) for gas exchange.
- The inner surface of the alveolus is covered by a thin film of moisture, allowing gases to dissolve before diffusing.
Marking: 1 mark for each valid adaptation with explanation (maximum 3 marks). Accept any three from the above.
(c) Explain why the concentration of carbon dioxide in exhaled air is higher than in inhaled air. [2 marks]
Answer: Inhaled air contains a low concentration of carbon dioxide (approximately 0.04%). In the body, cells carry out aerobic respiration, producing carbon dioxide as a waste product. This carbon dioxide diffuses from the respiring cells into the blood and is transported to the lungs, where it diffuses into the alveoli and is exhaled. Therefore, exhaled air has a higher CO₂ concentration (approximately 4%).
Marking: 1 mark for CO₂ produced by respiration; 1 mark for CO₂ diffusing into blood and then into alveoli for exhalation.
17. Effects of excessive alcohol consumption. [4 marks]
Answer:
Excessive long-term alcohol consumption has several harmful effects:
- Liver damage: Alcohol is broken down by the liver. Excessive consumption leads to fatty liver, alcoholic hepatitis, and eventually cirrhosis (scarring of liver tissue), which impairs liver function.
- Brain/nervous system: Alcohol is a depressant that slows down brain function, leading to impaired judgment, poor coordination, and slowed reaction times. Long-term abuse can cause permanent brain damage and memory loss.
- Digestive system: Alcohol irritates the stomach lining, causing gastritis and increasing the risk of stomach ulcers. It can also cause pancreatitis.
- Circulatory system: Excessive alcohol can increase blood pressure and weaken heart muscle, increasing the risk of heart disease and stroke.
Marking: 1 mark for each organ system discussed with a specific effect (maximum 4 marks). At least two organ systems must be covered. Accept other valid effects (e.g., foetal alcohol syndrome, increased cancer risk).
18. Response to decreased environmental temperature. [4 marks]
Answer:
When environmental temperature decreases, the body responds to maintain a core temperature of ~37°C through the following mechanisms:
- Vasoconstriction: Arterioles near the skin surface constrict, reducing blood flow to the skin. This reduces heat loss by radiation and convection from the body surface.
- Shivering: Skeletal muscles undergo rapid, involuntary contractions (shivering), which generates heat through increased respiration in muscle cells.
- Increased metabolic rate: The hormone thyroxine may be released to increase the metabolic rate of cells, generating more heat.
- Piloerection: Hairs on the skin stand up (goosebumps), trapping a layer of insulating air close to the skin (more effective in furry animals but limited in humans).
- Behavioural responses: The person may put on more clothing, seek shelter, or curl up to reduce exposed surface area.
These responses are coordinated by the hypothalamus, which acts as a thermostat, detecting blood temperature changes and initiating corrective mechanisms via the nervous and endocrine systems (negative feedback).
Marking: 1 mark for vasoconstriction with explanation; 1 mark for shivering with explanation; 1 mark for a third mechanism (e.g., increased metabolism, piloerection, or behavioural); 1 mark for reference to hypothalamus / negative feedback. Maximum 4 marks.
19. Blood group compatibility. [2 marks]
Answer:
A person with blood group A has antigen A on their red blood cells and anti-B antibodies in their plasma.
- Blood group O has no antigens on its red blood cells, so it will not react with the recipient's anti-A or anti-B antibodies. Therefore, group O blood can be safely transfused.
- Blood group B has antigen B on its red blood cells. The recipient's anti-B antibodies would bind to these B antigens, causing agglutination (clumping) of the donated red blood cells, which is dangerous and can be fatal.
Marking: 1 mark for explaining compatibility with group O (no antigens); 1 mark for explaining incompatibility with group B (anti-B antibodies cause agglutination).
20. Peristalsis. [2 marks]
Answer:
Peristalsis is the rhythmic, wave-like contraction and relaxation of the circular and longitudinal muscles in the walls of the alimentary canal (oesophagus, stomach, intestines). It pushes food along the digestive tract in one direction. It is important because it ensures that food is moved through the digestive system for digestion and absorption to occur, even against gravity.
Marking: 1 mark for describing the muscular contractions; 1 mark for explaining importance (moves food / unidirectional movement).
END OF ANSWER KEY