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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:
- This quiz contains 20 questions on Human Physiology.
- Answer ALL questions in the spaces provided.
- The number of marks for each question or part is shown in brackets.
- Write your answers clearly and use appropriate biological terminology.
Section A: Short Answer (10 marks)
Answer all questions in this section. Questions 1-5.
1. Define homeostasis and explain why it is essential for the survival of an organism. [2]
2. State the function of the hepatic portal vein in the human digestive system. [1]
3. A student runs 100 metres at maximum speed. Explain why the student continues to breathe heavily for several minutes after the race has ended. [2]
4. State one structural difference between an artery and a vein, and explain how this difference is related to the function of each vessel. [2]
5. Name the blood component responsible for transporting oxygen, and explain one adaptation of this component that makes it efficient at its function. [2]
Section B: Structured Response (10 marks)
Answer all questions in this section. Questions 6-10.
6. State the role of the diaphragm during inhalation. [1]
7. Figure 1 shows a diagram of a nephron, the functional unit of the kidney.
(a) Name the process that occurs at the glomerulus, where fluid is forced out of the blood into the Bowman's capsule. [1]
(b) Explain why red blood cells and large proteins are not found in the filtrate in a healthy kidney. [1]
(c) Glucose is present in the filtrate but absent in the urine of a healthy person. Explain where and how glucose is removed from the filtrate. [2]
8. A person eats a meal rich in carbohydrates. Describe how the hormone insulin helps to regulate the person's blood glucose concentration after the meal. [3]
9. The human heart pumps blood around the body in a double circulation.
(a) State what is meant by "double circulation." [1]
(b) Explain why the wall of the left ventricle is thicker than the wall of the right ventricle. [2]
10. Figure 2 shows an alveolus and its associated blood capillary.
(a) State two features of the alveolus that make it efficient for gas exchange. [2]
(b) Explain how carbon dioxide moves from the blood into the alveolus. [2]
Section C: Data-Based and Extended Response (10 marks)
Answer all questions in this section. Questions 11-15.
11. A person is diagnosed with kidney failure and requires dialysis treatment.
(a) Explain why the build-up of urea in the blood is dangerous. [1]
(b) Describe how a dialysis machine performs the function of a healthy kidney. [3]
12. A student investigated the effect of temperature on the activity of the enzyme amylase, which is found in human saliva. The student mixed amylase with starch solution at different temperatures and recorded the time taken for all the starch to be broken down. The results are shown in Table 1.
Table 1: Effect of Temperature on Amylase Activity
| Temperature (°C) | Time for starch breakdown (seconds) |
|---|---|
| 10 | 180 |
| 20 | 90 |
| 30 | 45 |
| 40 | 30 |
| 50 | 60 |
| 60 | No breakdown after 300 seconds |
(a) Identify the optimum temperature for amylase activity from the results. [1]
(b) Explain why the time taken for starch breakdown decreased between 10°C and 40°C. [2]
(c) Explain why no starch breakdown occurred at 60°C. [2]
(d) The student's body temperature is normally 37°C. Suggest why it is important that amylase works efficiently at this temperature. [1]
13. Describe the pathway of blood through the heart, starting from the vena cava and ending at the aorta. In your answer, name the chambers and valves the blood passes through, and state where the blood becomes oxygenated. [6]
Section D: Application and Analysis (10 marks)
Answer all questions in this section. Questions 14-20.
14. Explain how the structure of a capillary is adapted for its function in material exchange between blood and tissue cells. [2]
15. A person's blood pressure is measured as 120/80 mmHg. Explain what the two numbers represent and why maintaining a healthy blood pressure is important. [2]
16. Describe the role of the medulla oblongata in the regulation of breathing rate. [2]
17. Explain why a person with iron deficiency may feel tired and have a reduced ability to perform physical exercise. [2]
18. State two differences between aerobic and anaerobic respiration in humans. [2]
19. Explain how the structure of a villus in the small intestine is adapted for efficient absorption of digested food. [2]
20. A person drinks a large volume of water. Explain how the body responds to maintain water balance (osmoregulation). [2]
END OF QUIZ
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Answers
Secondary 3 Biology Quiz - Human Physiology: Answer Key
Total Marks: 40
Section A: Short Answer (10 marks)
1. Define homeostasis and explain why it is essential for the survival of an organism. [2]
Answer:
- Homeostasis is the maintenance of a constant internal environment within narrow limits. [1]
- It is essential because enzymes and other cellular processes function optimally only within specific conditions (e.g., temperature, pH, glucose concentration); deviation from these conditions can lead to enzyme denaturation, metabolic disruption, and ultimately death. [1]
Marking notes: Award 1 mark for the definition (must include "constant internal environment"). Award 1 mark for explaining why it is essential (must link to enzyme function or metabolic processes).
2. State the function of the hepatic portal vein in the human digestive system. [1]
Answer:
- The hepatic portal vein transports absorbed nutrients (e.g., glucose, amino acids) from the small intestine directly to the liver for processing, regulation, and storage before they enter general circulation.
Marking notes: Award 1 mark for stating transport of nutrients from intestine to liver. Accept "transports blood rich in absorbed nutrients from the small intestine to the liver."
3. A student runs 100 metres at maximum speed. Explain why the student continues to breathe heavily for several minutes after the race has ended. [2]
Answer:
- During the sprint, the muscles respired anaerobically due to insufficient oxygen supply, producing lactic acid. [1]
- After the race, the heavy breathing provides extra oxygen to break down the accumulated lactic acid (oxygen debt); the oxygen is also used to restore ATP and creatine phosphate levels in the muscles. [1]
Marking notes: Award 1 mark for identifying anaerobic respiration and lactic acid production. Award 1 mark for explaining that continued heavy breathing repays the oxygen debt (must mention breakdown of lactic acid or restoration of oxygen levels).
4. State one structural difference between an artery and a vein, and explain how this difference is related to the function of each vessel. [2]
Answer:
- Arteries have thicker muscular and elastic walls compared to veins. [1]
- The thick muscular and elastic walls of arteries enable them to withstand and maintain the high pressure of blood pumped from the heart, while veins have thinner walls because blood flows at lower pressure; veins also contain valves to prevent backflow. [1]
Marking notes: Award 1 mark for stating a valid structural difference (thicker walls in arteries, presence of valves in veins, smaller lumen in arteries relative to wall thickness). Award 1 mark for explaining how the difference relates to function (must link structure to pressure or backflow prevention).
5. Name the blood component responsible for transporting oxygen, and explain one adaptation of this component that makes it efficient at its function. [2]
Answer:
- Red blood cells (erythrocytes). [1]
- Adaptation: Red blood cells have a biconcave shape, which increases the surface area to volume ratio for faster diffusion of oxygen. OR Red blood cells lack a nucleus, providing more space for haemoglobin to carry oxygen. OR Red blood cells contain haemoglobin, which binds reversibly to oxygen. [1]
Marking notes: Award 1 mark for naming red blood cells. Award 1 mark for stating and explaining one adaptation (must link the structural feature to the functional advantage).
Section B: Structured Response (10 marks)
6. State the role of the diaphragm during inhalation. [1]
Answer:
- The diaphragm contracts and flattens, increasing the volume of the thoracic cavity and decreasing the pressure, causing air to be drawn into the lungs.
Marking notes: Award 1 mark for stating that the diaphragm contracts/flattens. Accept "moves downwards" as equivalent to flattens.
7. Figure 1 shows a diagram of a nephron, the functional unit of the kidney.
(a) Name the process that occurs at the glomerulus, where fluid is forced out of the blood into the Bowman's capsule. [1]
Answer: Ultrafiltration.
Marking notes: Award 1 mark for "ultrafiltration." Do not accept "filtration" alone unless qualified.
(b) Explain why red blood cells and large proteins are not found in the filtrate in a healthy kidney. [1]
Answer:
- Red blood cells and large proteins are too large to pass through the tiny pores in the glomerular basement membrane / capillary walls during ultrafiltration.
Marking notes: Award 1 mark for stating that these components are too large to pass through the filtration membrane/pores.
(c) Glucose is present in the filtrate but absent in the urine of a healthy person. Explain where and how glucose is removed from the filtrate. [2]
Answer:
- Glucose is removed from the filtrate in the proximal convoluted tubule. [1]
- Glucose is reabsorbed by active transport from the filtrate back into the blood capillaries surrounding the nephron. [1]
Marking notes: Award 1 mark for identifying the proximal convoluted tubule as the site. Award 1 mark for stating that glucose is reabsorbed by active transport.
8. A person eats a meal rich in carbohydrates. Describe how the hormone insulin helps to regulate the person's blood glucose concentration after the meal. [3]
Answer:
- After the meal, glucose is absorbed into the bloodstream, causing blood glucose concentration to rise. [1]
- The pancreas detects the increase in blood glucose and secretes insulin into the blood. [1]
- Insulin stimulates the liver and muscle cells to take up glucose and convert it to glycogen for storage; this reduces blood glucose concentration back to normal levels. [1]
Marking notes: Award 1 mark for stating that blood glucose rises after the meal. Award 1 mark for stating that the pancreas secretes insulin in response. Award 1 mark for explaining that insulin promotes glucose uptake and conversion to glycogen (must mention liver or muscle cells).
9. The human heart pumps blood around the body in a double circulation.
(a) State what is meant by "double circulation." [1]
Answer:
- Double circulation means that blood passes through the heart twice in one complete circuit of the body: once through the pulmonary circulation (heart to lungs and back) and once through the systemic circulation (heart to body and back).
Marking notes: Award 1 mark for stating that blood passes through the heart twice in one complete circuit. Accept reference to pulmonary and systemic circulations.
(b) 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), which requires higher pressure to overcome the greater resistance of the longer pathway. [1]
- The right ventricle only pumps blood to the nearby lungs (pulmonary circulation), which requires lower pressure. The thicker muscular wall of the left ventricle generates the higher pressure needed. [1]
Marking notes: Award 1 mark for stating that the left ventricle pumps blood to the whole body (or systemic circulation). Award 1 mark for explaining that thicker walls generate higher pressure to pump blood further.
10. Figure 2 shows an alveolus and its associated blood capillary.
(a) State two features of the alveolus that make it efficient for gas exchange. [2]
Answer:
- Feature 1: The alveolar wall is one-cell thick (thin epithelium), providing a short diffusion distance for gases. [1]
- Feature 2: The alveolus has a large surface area (due to its spherical shape and large number), increasing the rate of gas exchange. OR The alveolus is surrounded by a dense network of blood capillaries, maintaining a steep concentration gradient. OR The alveolar surface is moist, allowing gases to dissolve before diffusing. [1]
Marking notes: Award 1 mark for each valid feature with explanation. Accept any two of the listed features.
(b) Explain how carbon dioxide moves from the blood into the alveolus. [2]
Answer:
- Carbon dioxide diffuses from the blood into the alveolus down its concentration gradient. [1]
- The blood entering the capillary has a higher concentration of carbon dioxide than the alveolar air, so carbon dioxide moves from an area of higher concentration (blood) to an area of lower concentration (alveolus). [1]
Marking notes: Award 1 mark for stating diffusion down a concentration gradient. Award 1 mark for identifying the direction of the gradient (blood to alveolus).
Section C: Data-Based and Extended Response (10 marks)
11. A person is diagnosed with kidney failure and requires dialysis treatment.
(a) Explain why the build-up of urea in the blood is dangerous. [1]
Answer:
- Urea is a toxic waste product; its accumulation can lead to poisoning of cells, disruption of metabolic processes, and potentially death.
Marking notes: Award 1 mark for stating that urea is toxic or poisonous.
(b) Describe how a dialysis machine performs the function of a healthy kidney. [3]
Answer:
- The patient's blood is drawn from an artery and passed through a dialysis machine containing dialysis fluid separated by a partially permeable membrane. [1]
- The dialysis fluid contains the same concentration of useful substances (e.g., glucose, salts) as blood plasma, but no urea, so urea diffuses from the blood into the dialysis fluid down its concentration gradient. [1]
- The filtered blood is then returned to the patient's vein; this process removes waste products and excess water, mimicking the filtration function of the kidney. [1]
Marking notes: Award 1 mark for describing the setup (blood, membrane, dialysis fluid). Award 1 mark for explaining diffusion of urea down a concentration gradient. Award 1 mark for stating that useful substances are retained and blood is returned.
12. A student investigated the effect of temperature on the activity of the enzyme amylase, which is found in human saliva. The student mixed amylase with starch solution at different temperatures and recorded the time taken for all the starch to be broken down. The results are shown in Table 1.
Table 1: Effect of Temperature on Amylase Activity
| Temperature (°C) | Time for starch breakdown (seconds) |
|---|---|
| 10 | 180 |
| 20 | 90 |
| 30 | 45 |
| 40 | 30 |
| 50 | 60 |
| 60 | No breakdown after 300 seconds |
(a) Identify the optimum temperature for amylase activity from the results. [1]
Answer: 40°C.
Marking notes: Award 1 mark for 40°C.
(b) Explain why the time taken for starch breakdown decreased between 10°C and 40°C. [2]
Answer:
- As temperature increases, the kinetic energy of the enzyme and substrate molecules increases. [1]
- This leads to more frequent and successful collisions between enzyme and substrate, increasing the rate of reaction and thus decreasing the time taken for breakdown. [1]
Marking notes: Award 1 mark for mentioning increased kinetic energy or molecular movement. Award 1 mark for linking to increased collision frequency/successful collisions.
(c) Explain why no starch breakdown occurred at 60°C. [2]
Answer:
- At 60°C, the high temperature causes the enzyme amylase to denature. [1]
- Denaturation changes the shape of the active site, so the starch substrate can no longer bind to the enzyme, and the reaction cannot occur. [1]
Marking notes: Award 1 mark for stating denaturation. Award 1 mark for explaining that the active site shape is changed and substrate cannot bind.
(d) The student's body temperature is normally 37°C. Suggest why it is important that amylase works efficiently at this temperature. [1]
Answer:
- Amylase functions in the mouth and small intestine, which are at body temperature (37°C); efficient activity at this temperature ensures rapid digestion of starch into sugars for absorption.
Marking notes: Award 1 mark for linking to body temperature and digestive function.
13. Describe the pathway of blood through the heart, starting from the vena cava and ending at the aorta. In your answer, name the chambers and valves the blood passes through, and state where the blood becomes oxygenated. [6]
Answer:
- Deoxygenated blood enters the right atrium from the vena cava. [1]
- Blood passes through the tricuspid valve into the right ventricle. [1]
- The right ventricle contracts, pumping blood through the pulmonary valve into the pulmonary artery. [1]
- Blood travels to the lungs where it becomes oxygenated (gas exchange occurs in the alveolar capillaries). [1]
- Oxygenated blood returns to the left atrium via the pulmonary veins. [1]
- Blood passes through the bicuspid (mitral) valve into the left ventricle, then is pumped through the aortic valve into the aorta for distribution to the body. [1]
Marking notes: Award 1 mark for each correct step in sequence. Must include: right atrium, tricuspid valve, right ventricle, pulmonary valve/pulmonary artery, oxygenation in lungs, pulmonary veins, left atrium, bicuspid valve, left ventricle, aortic valve, aorta. Accept minor variations in terminology.
Section D: Application and Analysis (10 marks)
14. Explain how the structure of a capillary is adapted for its function in material exchange between blood and tissue cells. [2]
Answer:
- Capillary walls are one-cell thick (thin endothelium), providing a short diffusion distance for efficient exchange of gases, nutrients, and wastes. [1]
- Capillaries have a narrow lumen, which slows blood flow and allows more time for exchange; they are also highly branched, providing a large surface area. [1]
Marking notes: Award 1 mark for thin walls/short diffusion distance. Award 1 mark for narrow lumen/large surface area/slow blood flow.
15. A person's blood pressure is measured as 120/80 mmHg. Explain what the two numbers represent and why maintaining a healthy blood pressure is important. [2]
Answer:
- The first number (120) is the systolic pressure, the pressure in the arteries when the ventricles contract. The second number (80) is the diastolic pressure, the pressure when the ventricles relax. [1]
- Maintaining healthy blood pressure ensures adequate blood flow to deliver oxygen and nutrients to tissues without damaging blood vessels; high blood pressure can lead to vessel damage, stroke, or heart disease. [1]
Marking notes: Award 1 mark for correctly identifying systolic and diastolic pressures. Award 1 mark for explaining importance (adequate perfusion without vessel damage).
16. Describe the role of the medulla oblongata in the regulation of breathing rate. [2]
Answer:
- The medulla oblongata contains the respiratory centre that controls the rate and depth of breathing. [1]
- It detects changes in blood carbon dioxide concentration (via chemoreceptors) and sends nerve impulses to the diaphragm and intercostal muscles to adjust breathing rate accordingly. [1]
Marking notes: Award 1 mark for identifying the medulla oblongata as the control centre. Award 1 mark for linking to detection of CO2 and adjustment of breathing rate.
17. Explain why a person with iron deficiency may feel tired and have a reduced ability to perform physical exercise. [2]
Answer:
- Iron is a key component of haemoglobin in red blood cells, which transports oxygen. [1]
- Iron deficiency leads to reduced haemoglobin production, so less oxygen is delivered to muscles for aerobic respiration, resulting in fatigue and reduced exercise capacity. [1]
Marking notes: Award 1 mark for linking iron to haemoglobin/oxygen transport. Award 1 mark for explaining the consequence (less oxygen to muscles, fatigue).
18. State two differences between aerobic and anaerobic respiration in humans. [2]
Answer:
- Difference 1: Aerobic respiration requires oxygen, while anaerobic respiration does not. [1]
- Difference 2: Aerobic respiration produces a large amount of ATP (energy), while anaerobic respiration produces a small amount of ATP. OR Aerobic respiration produces carbon dioxide and water as waste products, while anaerobic respiration produces lactic acid. [1]
Marking notes: Award 1 mark for each valid difference. Accept any two clear contrasts.
19. Explain how the structure of a villus in the small intestine is adapted for efficient absorption of digested food. [2]
Answer:
- The villus has a thin epithelium (one-cell thick), providing a short diffusion distance for absorbed nutrients. [1]
- The villus contains a dense network of blood capillaries and a lacteal, which rapidly transport absorbed nutrients away, maintaining a concentration gradient. OR The villus has microvilli on its surface, increasing the surface area for absorption. [1]
Marking notes: Award 1 mark for thin epithelium/short diffusion distance. Award 1 mark for rich blood supply/lacteal/microvilli/large surface area.
20. A person drinks a large volume of water. Explain how the body responds to maintain water balance (osmoregulation). [2]
Answer:
- The excess water is absorbed into the blood, causing blood water potential to increase; this is detected by the hypothalamus in the brain. [1]
- The pituitary gland releases less ADH (antidiuretic hormone), so the kidneys reabsorb less water from the filtrate, producing a larger volume of dilute urine to remove the excess water. [1]
Marking notes: Award 1 mark for detecting increased water potential and reduced ADH secretion. Award 1 mark for explaining that less water is reabsorbed in the kidneys, resulting in more dilute urine.
END OF ANSWER KEY