Secondary 4 Pure Biology Cells Biomolecules Quiz

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Secondary 4 Pure Biology Quiz - Cells Biomolecules

Name: ___________________________
Class: ___________
Date: ___________
Score: ___________ / 40

Duration: 50 minutes
Total Marks: 40

Instructions:

• Answer all 20 questions.
• Section A: Multiple Choice (1 mark each)
• Section B: Short Answer (1–2 marks each)
• Section C: Structured & Data-Based (2–4 marks each)
• Write your answers clearly in the spaces provided.

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Section A: Multiple Choice (Questions 1–5)

1. Which of the following cell structures is the site of protein synthesis?
   A. Mitochondrion
   B. Ribosome
   C. Golgi body
   D. Nucleus
   [ ]

2. Which biomolecule is mainly used for long-term energy storage and insulation in humans?
   A. Carbohydrate
   B. Protein
   C. Fat
   D. Starch
   [ ]

3. The movement of water molecules from a region of higher water potential to lower water potential through a partially permeable membrane is called:
   A. Diffusion
   B. Active transport
   C. Osmosis
   D. Translocation
   [ ]

4. Which food test uses iodine solution to detect the presence of starch?
   A. Benedict’s test
   B. Biuret test
   C. Ethanol test
   D. Iodine test
   [ ]

5. According to the lock-and-key model of enzyme action, the substrate binds to the enzyme at the:
   A. Active site
   B. Cell membrane
   C. Nucleus
   D. Mitochondrion
   [ ]

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Section B: Short Answer (Questions 6–10)

6. Name the cells through which water is absorbed from the soil by plant roots.
   _______________________________________ [1]

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

8. Name the enzyme that breaks down starch into maltose in the human mouth.
   _______________________________________ [1]

9. Give one element that is present in proteins but not in carbohydrates.
   _______________________________________ [1]

10. What is the term for the shrinkage of an animal cell when placed in a concentrated solution?
    _______________________________________ [1]

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Section C: Structured & Data-Based (Questions 11–20)

11. The diagram below shows an electron micrograph of a plant cell with labelled structures.

Image pending generation: diagram for Q11.

(a) Which labelled structure (A–F) is the site of ATP production? [1]
(b) Which labelled structure carries out photosynthesis? [1]

12. Explain why a decrease in the water potential of blood (due to very high glucose concentration) may damage red blood cells. [3]

13. The diagram shows three plant cells P, Q and R placed in different sugar solutions. Arrows indicate net water movement by osmosis.

Image pending generation: diagram for Q13.

State the direction of net water movement for cell Q and explain your answer. [2]

14. A student tested a food sample using Benedict’s solution and obtained a green precipitate after heating. What does this indicate about the sample? [2]

15. Describe how the structure of a red blood cell is adapted to its function of transporting oxygen. [3]

16. The table below shows the effect of temperature on the rate of an enzyme-controlled reaction.

Temperature (°C)	Rate of reaction (arbitrary units)
20	12
30	25
40	40
50	38
60	10

(a) Plot the data on a graph (temperature on x-axis, rate on y-axis). [2]
(b) State the optimum temperature for this enzyme and explain why the rate falls after this temperature. [2]

17. Name the process by which root hair cells absorb mineral ions from a dilute soil solution against a concentration gradient, and state why it requires energy. [2]

18. Compare the structure of a typical animal cell and a typical plant cell by stating two differences. [2]

19. A protein is made of many amino acids joined together.
    (a) What is the name of the bond formed between amino acids? [1]
    (b) State the role of proteins in the human body. [1]

20. The figure shows a graph of cell division over time.

Image pending generation: graph for Q20.

Complete the line from Time 4 to Time 6 to show formation of cell A. Label the point at which cell A is first formed with the words “formation of cell A”. [2]

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Secondary 4 Pure Biology Quiz - Cells Biomolecules: Answer Key

Total Marks: 40
Topic: Cells Biomolecules

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Section A: Multiple Choice

1. B [1]
   Teaching note: Ribosomes are the sites of protein synthesis. Mitochondria produce ATP, Golgi body modifies proteins, nucleus stores DNA.

2. C [1]
   Teaching note: Fats store energy long-term and insulate. Carbohydrates are short-term energy; proteins are for growth/repair.

3. C [1]
   Teaching note: Osmosis is water movement through partially permeable membrane down water potential gradient.

4. D [1]
   Teaching note: Iodine turns blue-black with starch. Benedict’s detects reducing sugar, biuret detects protein, ethanol detects fat.

5. A [1]
   Teaching note: Substrate fits enzyme active site like key in lock.

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Section B: Short Answer

6. Root hair cells [1]
   Teaching note: Not xylem or epidermis. Root hair cells increase surface area for water uptake.

7. Site of respiration / ATP production [1]
   Teaching note: Mitochondria are power stations of the cell.

8. Amylase [1]
   Teaching note: Salivary amylase in mouth breaks starch to maltose.

9. Nitrogen (or sulphur) [1]
   Teaching note: Proteins contain C, H, O, N; carbohydrates only C, H, O.

10. Crenation [1]
    Teaching note: Animal cells shrink in hypertonic solution; plant cells plasmolyse.

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Section C: Structured & Data-Based

11. (a) C [1] (b) B [1]
    Teaching note: Mitochondrion (C) produces ATP; chloroplast (B) photosynthesises. Common trap: confusing ribosome with mitochondrion.

12. [3 marks]

• High glucose decreases water potential of blood. [1]
• Water moves out of red blood cells by osmosis (down water potential gradient). [1]
• RBCs lose water, shrink (crenate), may be damaged / cannot function. [1]
  Teaching note: Must link decreased ψ to water loss and consequence.

13. [2 marks]

• No net movement (isotonic). [1]
• Water potential inside Q equals outside, so no net osmosis. [1]
  Teaching note: Q is isotonic; arrows absent means equilibrium.

14. [2 marks]

• Sample contains reducing sugar. [1]
• Green precipitate indicates low to moderate amount (not high which would be red/brown). [1]
  Teaching note: Benedict’s green = some reducing sugar present.

15. [3 marks]

• Biconcave shape increases surface area for oxygen diffusion. [1]
• No nucleus allows more space for haemoglobin. [1]
• Contains haemoglobin to bind oxygen. [1]
  Teaching note: Adaptations link directly to oxygen transport.

16. (a) [2 marks] Graph plotted: points (20,12),(30,25),(40,40),(50,38),(60,10) joined. Axes labelled.
    (b) [2 marks] Optimum = 40°C [1]; above this enzyme denatures, active site changes shape, rate falls. [1]

17. [2 marks] Active transport [1]; requires energy (ATP) because moving against concentration gradient [1].

18. [2 marks] Any two: plant has cell wall, animal does not [1]; plant has chloroplast, animal does not [1]; plant has large vacuole, animal small/no vacuole.

19. (a) Peptide bond [1] (b) Growth and repair of tissues / make enzymes / antibodies [1]

20. [2 marks] Line from 4h to 6h rising 1→2 [1]; label “formation of cell A” at 6h [1].
    Teaching note: Cytokinesis completes at 6h; mark exactly there.