Secondary 4 Pure Biology Cells Biomolecules Quiz

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Secondary 4 Pure Biology Quiz - Cells Biomolecules

Name: ____________________
Class: ____________________
Date: ____________________
Score: ________ / 60

Duration: 60 Minutes
Total Marks: 60

Instructions:

• Answer all questions in the spaces provided.
• Use a blue or black pen.
• For structured questions, ensure your explanations are detailed and use biological terminology.

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Section A: Cell Structure and Organisation (Questions 1-7)

1. State the function of the cell wall in a plant cell. [1]
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2. Name the organelle responsible for the synthesis of proteins. [1]
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3. Compare the typical structure of an animal cell and a plant cell. State one difference. [1]
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4. A cell contains a high number of mitochondria. Suggest the likely function of this cell and explain your reasoning. [2]
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5. Describe how a root hair cell is adapted to its function of absorbing water and mineral ions from the soil. [3]
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6. Identify the organelle that modifies, sorts, and packages proteins for secretion from the cell. [1]
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7. Explain why red blood cells in mammals lack a nucleus upon maturity. [2] ___________________________________________________________________________ ___________________________________________________________________________

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Section B: Movement of Substances (Questions 8-14)

8. Define the term diffusion. [2]
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9. Explain the process of osmosis. [2]
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10. A plant cell is placed in a solution with a very low water potential (hypertonic). Describe the state of the cell after 30 minutes. [2]
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11. Distinguish between diffusion and active transport in terms of energy requirement and concentration gradients. [3]
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12. Explain why active transport is necessary for the absorption of mineral ions by root hair cells from the soil. [3]
    ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________

13. In the human small intestine, glucose is absorbed into the villi. Explain why this process often requires active transport. [3]
    ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________

14. Predict the effect on a red blood cell if it is placed in distilled water. Explain your answer. [3]
    ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________

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Section C: Biological Molecules and Enzymes (Questions 15-20)

15. State the chemical elements found in a protein molecule. [1]
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16. Name the chemical test used to identify the presence of reducing sugars and state the positive result. [2]
    ___________________________________________________________________________ ___________________________________________________________________________

17. Describe the "lock-and-key" model of enzyme action. [3]
    ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________

18. Explain why an enzyme's activity decreases significantly when the temperature is raised far above its optimum. [3]
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19. A student investigates the effect of pH on the rate of reaction of an enzyme. Describe the expected relationship between pH and the rate of reaction. [3]
    ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________

20. Compare the roles of carbohydrates and fats in the human body. [4]
    ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________

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Answer Key: Secondary 4 Pure Biology Quiz - Cells Biomolecules

1. Function of cell wall

• Provides structural support/maintains cell shape.
• Prevents the cell from bursting when turgid. (1 mark)

2. Protein synthesis organelle

• Ribosome. (1 mark)

3. Animal vs Plant cell difference

• Plant cells have a cell wall / chloroplasts / large central vacuole; animal cells do not.
• Animal cells have centrioles; plant cells generally do not. (1 mark)

4. High mitochondria function

• Function: High energy demand (e.g., muscle cell, sperm cell, secretory cell).
• Reasoning: Mitochondria are the site of aerobic respiration, which produces ATP/energy. (2 marks)

5. Root hair cell adaptation

• Long extension/hair-like projection $\rightarrow$ increases surface area for faster absorption of water/ions.
• Thin cell wall $\rightarrow$ reduces diffusion distance.
• High concentration of solutes in cytoplasm $\rightarrow$ maintains water potential gradient. (3 marks)

6. Packaging organelle

• Golgi body / Golgi apparatus. (1 mark)

7. Red blood cell nucleus

• To provide more space for haemoglobin.
• This allows the cell to carry more oxygen. (2 marks)

8. Definition of diffusion

• The net movement of particles from a region of higher concentration to a region of lower concentration.
• Down a concentration gradient. (2 marks)

9. Process of osmosis

• The net movement of water molecules from a region of higher water potential to a region of lower water potential.
• Through a partially permeable membrane. (2 marks)

10. Plant cell in hypertonic solution

• The cell becomes plasmolyzed.
• Water leaves the vacuole/cytoplasm by osmosis; the cell membrane pulls away from the cell wall. (2 marks)

11. Diffusion vs Active Transport

• Energy: Diffusion is passive (no ATP); Active transport requires energy (ATP).
• Gradient: Diffusion is down the gradient; Active transport is against/up the gradient. (3 marks)

12. Active transport in roots

• Mineral ion concentration in soil is often lower than inside the root cell.
• Ions must move against the concentration gradient.
• Energy is required to pump ions into the cell via carrier proteins. (3 marks)

13. Glucose absorption in villi

• After most glucose is absorbed by diffusion, the remaining glucose concentration in the lumen is lower than in the blood/cell.
• To ensure maximum absorption of all available glucose, active transport is used to move glucose against the gradient. (3 marks)

14. RBC in distilled water

• The RBC will swell and burst (haemolysis).
• Distilled water has a higher water potential than the cell cytoplasm.
• Water moves into the cell by osmosis; since there is no cell wall to resist the pressure, the membrane ruptures. (3 marks)

15. Protein elements

• Carbon, Hydrogen, Oxygen, Nitrogen (C, H, O, N). (1 mark)

16. Reducing sugar test

• Test: Benedict's test.
• Result: Color change from blue to green/yellow/orange/brick-red precipitate. (2 marks)

17. Lock-and-key model

• The enzyme has a specific 3D shape called the active site.
• The substrate has a complementary shape that fits exactly into the active site.
• An enzyme-substrate complex is formed, lowering activation energy to catalyze the reaction. (3 marks)

18. Temperature effect (Denaturation)

• High thermal energy breaks the bonds (hydrogen/disulfide) maintaining the enzyme's tertiary structure.
• The active site changes shape and is no longer complementary to the substrate.
• The enzyme is denatured; no enzyme-substrate complexes can form. (3 marks)

19. pH relationship

• The rate of reaction increases as pH approaches the optimum pH.
• At the optimum pH, the rate of reaction is at its maximum.
• As pH moves away from the optimum (either more acidic or alkaline), the rate decreases as the enzyme denatures. (3 marks)

20. Carbohydrates vs Fats

• Carbohydrates: Primary source of immediate energy (glucose); stored as glycogen in animals/starch in plants.
• Fats: Long-term energy storage; provide thermal insulation; protect internal organs.
• Both are used for energy production via respiration. (4 marks)