Secondary 3 Combined Science Life Sciences Quiz

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Secondary 3 Combined Science Quiz - Life Sciences

Name: ____________________ Class: ____________________ Date: ____________________ Score: ________ / 55

Duration: 60 minutes
Total Marks: 55
Instructions: Answer all questions. Use scientific terminology. For structured questions, ensure your explanations are complete.

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Section A: Cell Biology & Transport (Questions 1–6)

1. State the function of the mitochondria in a cell. [1]

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2. A student observes a cell under a microscope and notices that the cell membrane has shrunk away from the cell wall. Describe the state of this cell. [1]

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3. Explain why a pancreatic cell contains a large number of ribosomes. [1]

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4. Define the term osmosis. [2]

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5. A potato cube is placed in a beaker of distilled water for two hours. (a) Predict the change in the mass of the potato cube. [1]

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   (b) Explain your answer to (a) in terms of water potential. [2]

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6. State one function and one adaptation of the xylem tissue in plants. [2] Function: _________________________________________________________________ Adaptation: _______________________________________________________________

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Section B: Human Physiology - Nutrition & Digestion (Questions 7–11)

7. Name the enzyme that digests proteins in the stomach. [1]

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8. Explain why the concentration of amino acids in the small intestine increases and then subsequently decreases. [2]

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9. State the role of bile in the digestion of fats. [2]

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10. Describe the "lock and key" hypothesis in relation to how an enzyme works. [3]

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11. A table shows the relative amount of maltose in the alimentary canal. (a) In which region of the alimentary canal does the concentration of maltose peak? [1]

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    (b) Name the enzyme responsible for the further breakdown of maltose. [1]

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Section C: Human Physiology - Transport & Respiration (Questions 12–17)

12. State the main difference between the wall thickness of the left ventricle and the right ventricle. [1]

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13. Describe the pathway of oxygenated blood from the lungs to the rest of the body. [4]

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14. State the function of the valves in the heart. [1]

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15. Write the word equation for aerobic respiration in humans. [2]

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16. Compare aerobic and anaerobic respiration in humans. [4] (i) Requirement for oxygen: _________________________________________________ (ii) End products: _________________________________________________________ (iii) Energy yield: _________________________________________________________ (iv) Word equation for anaerobic respiration: __________________________________

17. Explain why a person breathes more rapidly and deeply during vigorous exercise. [3]

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Section D: Plant Physiology & Ecology (Questions 18–20)

18. Describe the pathway of water from the soil to the atmosphere in a plant. [5]

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19. In an experiment to measure the rate of photosynthesis, a glass heat shield is placed between the light source and the plant. State the purpose of this shield. [1]

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20. Suggest one way a student can vary the light intensity in an experiment investigating the rate of photosynthesis. [1]

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Answer Key - Secondary 3 Combined Science Quiz (Life Sciences)

1. To provide energy for the cell / Site of aerobic respiration. [1]
2. Plasmolysed. [1]
3. Pancreatic cells produce large amounts of enzymes (proteins), and ribosomes are the site of protein synthesis. [1]
4. The net movement of water molecules from a region of higher water potential to a region of lower water potential [1] through a partially permeable membrane [1]. [2]
5. (a) Increase. [1] (b) Water potential of distilled water is higher than that of the potato cells [1]; water enters the potato cells by osmosis [1]. [2]
6. Function: Transport water and mineral salts from roots to leaves / Mechanical support. [1] Adaptation: Lignified walls for strength / Hollow lumen / No cross-walls. [1] [2]
7. Pepsin / Protease. [1]
8. Proteins/polypeptides are digested by protease into amino acids, increasing their concentration [1]; amino acids are then absorbed into the blood through the small intestine wall, decreasing their concentration [1]. [2]
9. Emulsifies fats [1] to increase the surface area for lipase to act upon [1]. [2]
10. The enzyme has a specific active site shape [1] that is complementary to the shape of a specific substrate [1]. The substrate fits into the active site to form an enzyme-substrate complex [1]. [3]
11. (a) Small intestine (duodenum). [1] (b) Maltase. [1]
12. The left ventricle wall is thicker than the right ventricle wall. [1]
13. Oxygenated blood returns from lungs via pulmonary veins to left atrium [1] $\rightarrow$ left atrium contracts, pushing blood into left ventricle [1] $\rightarrow$ left ventricle contracts [1] $\rightarrow$ blood is forced through the aortic valve into the aorta [1]. [4]
14. To prevent the backflow of blood. [1]
15. Glucose + Oxygen $\rightarrow$ Carbon dioxide + Water + Energy [2]
16. (i) Aerobic requires oxygen; Anaerobic does not. [1] (ii) Aerobic: $\text{CO}_2$ and $\text{H}_2\text{O}$; Anaerobic: Lactic acid. [1] (iii) Aerobic releases significantly more energy than anaerobic. [1] (iv) Glucose $\rightarrow$ Lactic acid + Energy [1]. [4]
17. To supply more oxygen to the muscle cells [1] for aerobic respiration to produce more energy [1] and to remove carbon dioxide faster [1]. [3]
18. Water absorbed by root hair cells from soil [1] $\rightarrow$ moves through cortex/endodermis [1] $\rightarrow$ enters xylem in root [1] $\rightarrow$ transported up stem via xylem [1] $\rightarrow$ exits via stomata in leaves through transpiration [1]. [5]
19. To ensure the temperature remains constant / To prevent the heat from the lamp from affecting the plant. [1]
20. Change the distance of the light source from the plant / Change the number of bulbs / Change the wattage of the bulb. [1]