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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.
Write your answers in the spaces provided.
The number of marks is given in brackets [ ] at the end of each question or part question.

Section A: Multiple Choice (Questions 1–5)

Choose the correct answer for each question. Each question carries 1 mark.

1. Which of the following correctly describes the function of the enzyme pepsin? A. It breaks down starch into maltose in the mouth. B. It breaks down proteins into polypeptides in the stomach. C. It breaks down fats into fatty acids and glycerol in the duodenum. D. It neutralises hydrochloric acid in the small intestine.

2. A patient has a blockage in their coronary artery. Which part of the heart muscle is most likely to be deprived of oxygen? A. The left atrium B. The right atrium C. The left ventricle D. The right ventricle

3. During vigorous exercise, the concentration of lactic acid in the muscles increases. What is the primary reason for this? A. The body is producing excess carbon dioxide. B. The muscles are respiring anaerobically due to insufficient oxygen supply. C. The liver is converting glucose to glycogen too rapidly. D. The rate of aerobic respiration has exceeded the oxygen supply.

4. Which structure in the nephron is responsible for the ultrafiltration of blood? A. The collecting duct B. The loop of Henle C. The glomerulus and Bowman’s capsule D. The proximal convoluted tubule

5. In the reflex arc for withdrawing a hand from a hot object, what is the role of the relay neurone? A. To detect the heat stimulus. B. To transmit the impulse from the sensory neurone to the motor neurone. C. To carry the impulse to the brain for conscious perception. D. To stimulate the muscle to contract.

Section B: Structured Questions - Digestion and Circulation (Questions 6–10)

Answer all questions in the spaces provided.

6. Which hormone is responsible for lowering blood glucose levels after a meal? A. Glucagon B. Adrenaline C. Insulin D. Thyroxine

7. What is the main function of the villi in the small intestine? A. To secrete digestive enzymes. B. To increase the surface area for absorption of digested food. C. To churn food mechanically. D. To absorb water from undigested food.

8. Which component of blood is primarily responsible for transporting oxygen? A. Plasma B. Platelets C. White blood cells D. Red blood cells

9. During inhalation, which of the following changes occurs in the thoracic cavity? A. The diaphragm relaxes and moves upwards. B. The external intercostal muscles relax. C. The volume of the thoracic cavity decreases. D. The pressure in the thoracic cavity decreases.

10. A person moves from a dark room into bright sunlight. What happens to the pupil of their eye? A. The circular muscles contract, and the pupil constricts. B. The radial muscles contract, and the pupil dilates. C. The circular muscles relax, and the pupil dilates. D. The radial muscles relax, and the pupil constricts.

Section C: Structured Questions - Excretion and Coordination (Questions 11–15)

Answer all questions in the spaces provided.

11. The diagram below represents the human heart.

Image pending generation for this question.

(a) Identify the chamber that pumps oxygenated blood to the rest of the body. [1]

(b) Explain why the wall of chamber D is thicker than the wall of chamber B. [2]

12. Enzymes are biological catalysts. Amylase is an enzyme found in saliva.

(a) State the substrate and the product of the reaction catalysed by amylase. [2] Substrate: __________________________ Product: __________________________

(b) Explain why amylase stops working effectively once it reaches the stomach. [2]

13. The table below shows the composition of blood plasma, glomerular filtrate, and urine.

Substance	Plasma (g/100cm³)	Glomerular Filtrate (g/100cm³)	Urine (g/100cm³)
Protein	8.0	0.0	0.0
Glucose	0.1	0.1	0.0
Urea	0.03	0.03	2.0

(a) Explain why there is no protein in the glomerular filtrate. [2]

(b) Explain why the concentration of urea is much higher in urine than in plasma. [2]

14. Homeostasis is the maintenance of a constant internal environment.

(a) Define homeostasis. [1]

(b) Describe how the skin helps to regulate body temperature when a person is in a hot environment. Include two mechanisms in your answer. [3]

15. The human nervous system allows for rapid response to stimuli.

(a) Distinguish between a voluntary action and a reflex action. [2]

(b) Explain the importance of reflex actions to an organism. [1]

Section D: Free Response Questions (Questions 16–20)

Answer the questions in the spaces provided.

16. Coronary Heart Disease (CHD) is a major cause of death worldwide.

(a) Describe how a diet high in saturated fats can lead to CHD. [3]

(b) Suggest one lifestyle change, other than diet, that can reduce the risk of CHD. [1]

17. (a) Describe the process of digestion of starch in the human alimentary canal. Refer to the enzymes involved and the locations where digestion occurs. [3]

(b) Describe how the end-products of starch digestion are absorbed into the blood. [2]

18. (a) Describe the process of digestion of protein in the human alimentary canal. Refer to the enzymes involved and the locations where digestion occurs. [3]

(b) Explain how amino acids are transported from the small intestine to the rest of the body. [2]

19. The liver plays a central role in homeostasis.

(a) Explain why the liver is important in the regulation of blood glucose levels when blood glucose is high. [2]

(b) Explain why the liver is important in the regulation of blood glucose levels when blood glucose is low. [2]

20. Compare the nervous system and the endocrine system in terms of: (a) The speed of transmission. [1]

(b) The duration of the effect. [1]

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Answers

O-Level Biology Quiz - Human Physiology (Answer Key)

Section A: Multiple Choice

1. B
Reasoning: Pepsin is a protease found in the stomach that breaks down proteins into polypeptides.

2. C
Reasoning: The coronary arteries supply blood to the heart muscle itself. The left ventricle has the thickest muscle wall and highest oxygen demand, making it highly susceptible to ischemia if supply is blocked.

3. B
Reasoning: During vigorous exercise, oxygen supply may not meet demand. Muscles switch to anaerobic respiration, producing lactic acid.

4. C
Reasoning: Ultrafiltration occurs in the glomerulus, where blood is filtered into the Bowman’s capsule.

5. B
Reasoning: The relay neurone (interneurone) is located in the spinal cord and connects the sensory neurone to the motor neurone.

Section B: Structured Questions - Digestion and Circulation

6. C
Reasoning: Insulin is secreted by the pancreas to lower blood glucose by promoting uptake into cells and conversion to glycogen.

7. B
Reasoning: Villi are finger-like projections that vastly increase the surface area for efficient absorption of nutrients.

8. D
Reasoning: Red blood cells contain haemoglobin, which binds to oxygen for transport.

9. D
Reasoning: During inhalation, the diaphragm contracts (moves down) and external intercostals contract (ribs move up/out). This increases volume, which decreases pressure, drawing air in.

10. A
Reasoning: In bright light, the circular muscles of the iris contract to constrict the pupil, reducing light entry to protect the retina.

Section C: Structured Questions - Excretion and Coordination

11. (a) D (Left Ventricle) [1] (b) The left ventricle pumps blood to the entire body (systemic circulation), which requires high pressure to overcome resistance in distant vessels. The right ventricle only pumps blood to the lungs (pulmonary circulation), which is a shorter distance and offers less resistance. [2] (c) Bicuspid valve (or Mitral valve) [1]

12. (a) Substrate: Starch [1]
Product: Maltose [1] (b) The stomach contains hydrochloric acid, creating a low pH (acidic) environment. Amylase works best at a neutral/alkaline pH. The acidic conditions denature the enzyme, changing the shape of its active site so it can no longer bind to the substrate. [2]

13. (a) Protein molecules are too large to pass through the pores of the capillary walls in the glomerulus. Only small molecules like water, glucose, and urea are filtered through. [2] (b) As water is reabsorbed from the filtrate back into the blood (in the proximal convoluted tubule and loop of Henle), the volume of fluid decreases. Since urea is not fully reabsorbed, its concentration increases significantly in the remaining fluid (urine). [2]

14. (a) The maintenance of a constant internal environment within narrow limits despite changes in the external environment. [1] (b) 1. Vasodilation: Blood vessels near the skin surface dilate, allowing more blood flow to the surface, losing heat by radiation.
2. Sweating: Sweat glands secrete sweat onto the skin surface; evaporation of sweat removes heat energy from the body.
(Accept: Hair erector muscles relax to flatten hairs, reducing insulation) [3]

15. (a) Voluntary actions are conscious and controlled by the brain (cerebrum), whereas reflex actions are involuntary, rapid, and controlled by the spinal cord or brainstem without conscious thought. [2] (b) They provide immediate protection against harm (e.g., withdrawing from heat) before the brain processes the pain, preventing tissue damage. [1]

Section D: Free Response Questions

16. (a) High saturated fat intake leads to high cholesterol levels in the blood. Cholesterol deposits on the inner walls of coronary arteries, forming plaques (atheroma). This narrows the artery lumen, restricting blood flow and reducing oxygen supply to the heart muscle. [3] (b) Stop smoking / Exercise regularly / Reduce stress. [1]

17. (a) Digestion of Starch:

Mouth: Salivary amylase breaks down starch into maltose.
Duodenum (Small Intestine): Pancreatic amylase continues the breakdown of starch into maltose.
Ileum: Membrane-bound enzyme maltase breaks down maltose into glucose.
(3 marks for correct enzyme/location/product sequence) [3]

(b) Absorption:

Glucose is absorbed into the blood capillaries in the villi.
This occurs via active transport (against concentration gradient) and facilitated diffusion.
It is then transported via the hepatic portal vein to the liver. [2]

18. (a) Digestion of Protein:

Stomach: Pepsin (protease) breaks down proteins into polypeptides. HCl provides optimal acidic pH.
Duodenum: Trypsin (from pancreas) breaks down proteins/polypeptides into smaller peptides.
Ileum: Peptidases (membrane-bound) break down peptides into amino acids.
(3 marks for correct enzyme/location/product sequence) [3]

(b) Transport:

Amino acids are absorbed into the blood capillaries in the villi.
They are transported via the hepatic portal vein to the liver, then into the general circulation to body cells. [2]

19. (a) When blood glucose is high, the pancreas secretes insulin. Insulin causes the liver to convert glucose into glycogen for storage (glycogenesis). This lowers blood glucose levels. [2]

(b) When blood glucose is low, the pancreas secretes glucagon. Glucagon causes the liver to convert stored glycogen back into glucose (glycogenolysis) and release it into the blood. This raises blood glucose levels. [2]

20. (a) Nervous system: Fast / Rapid. Endocrine system: Slow. [1] (b) Nervous system: Short-lived / Brief. Endocrine system: Long-lasting. [1] (c) Nervous system: Electrical impulses along neurones. Endocrine system: Chemical hormones transported in the blood. [2]