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Secondary 3 Biology Cells Biomolecules Quiz
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Questions
Secondary 3 Biology Quiz - Cells Biomolecules
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 for each question or part is given in brackets [ ].
- Diagrams are not drawn to scale unless stated.
Section A: Multiple Choice Questions (Questions 1–5)
Choose the correct answer and write the letter in the box provided.
1. A student observes a cell under an electron microscope. The cell contains a nucleus, mitochondria, and ribosomes, but lacks a cell wall and chloroplasts. Which type of cell is this?
[ ] A. Palisade mesophyll cell
[ ] B. Root hair cell
[ ] C. White blood cell
[ ] D. Yeast cell
2. Which of the following correctly matches the organelle with its primary function?
[ ] A. Golgi apparatus – Synthesis of lipids
[ ] B. Mitochondrion – Site of aerobic respiration
[ ] C. Ribosome – Packaging of proteins
[ ] D. Nucleus – Production of ATP
3. An actively secreting cell (e.g., a pancreatic cell producing insulin) is supplied with radioactive amino acids. Which sequence correctly shows the path of radioactivity through the cell structures?
[ ] A. Nucleus → Ribosome → Golgi → Vesicle
[ ] B. Ribosome → Rough ER → Golgi → Vesicle
[ ] C. Rough ER → Ribosome → Golgi → Cell Membrane
[ ] D. Golgi → Rough ER → Ribosome → Vesicle
4. Why do red blood cells lack a nucleus?
[ ] A. To allow the cell to divide more rapidly.
[ ] B. To increase the surface area for gas exchange.
[ ] C. To provide more space for haemoglobin to carry oxygen.
[ ] D. To prevent the cell from using oxygen for its own respiration.
5. Which of the following statements about enzymes is incorrect?
[ ] A. Enzymes are biological catalysts made of protein.
[ ] B. Enzymes lower the activation energy of a reaction.
[ ] C. Enzymes are destroyed after they catalyse a reaction.
[ ] D. Enzymes are specific to their substrates due to the shape of the active site.
Section B: Structured Questions (Questions 6–15)
6. The diagram below represents a typical plant cell.
(Imagine a diagram showing a plant cell with labels A, B, C, D)
- A: Cell Wall
- B: Chloroplast
- C: Vacuole
- D: Nucleus
(a) State the function of structure B.
[1]
(b) Structure C contains cell sap. Explain how this structure helps maintain the shape of the plant.
[2]
7. A student investigates the effect of temperature on the activity of the enzyme amylase.
The results are shown in the table below:
| Temperature (°C) | Time taken for starch to disappear (s) |
|---|---|
| 20 | 120 |
| 30 | 60 |
| 40 | 30 |
| 50 | 45 |
| 60 | > 300 (Starch remains) |
(a) Describe the trend in enzyme activity as the temperature increases from 20°C to 40°C.
[2]
(b) Explain why no starch digestion occurred at 60°C.
[3]
8. Compare the structures of a typical animal cell and a typical plant cell by completing the table below.
| Feature | Animal Cell | Plant Cell |
|---|---|---|
| Cell Wall | Absent | Present |
| Chloroplasts | (a) _______________ | Present |
| Vacuole | (b) _______________ | Large, permanent central vacuole |
| Shape | (c) _______________ | Regular / Fixed shape |
[3]
9. Muscle cells require large amounts of energy to contract.
(a) Name the organelle that is present in high numbers in muscle cells to meet this energy demand.
[1]
(b) Explain why this organelle is essential for muscle function.
[2]
10. The lock-and-key hypothesis explains enzyme specificity.
(a) Define the term active site.
[1]
(b) Explain what happens to the enzyme-substrate complex after the reaction is complete.
[2]
11. Root hair cells are specialised for absorption.
(a) State one structural adaptation of a root hair cell that increases its efficiency in absorbing water.
[1]
(b) Explain how this adaptation helps in the uptake of water by osmosis.
[2]
12. Biological molecules can be identified using chemical tests.
Complete the table below:
| Biological Molecule | Reagent Used | Positive Result Colour |
|---|---|---|
| Starch | Iodine Solution | (a) _______________ |
| Reducing Sugar | (b) _______________ | Brick-red precipitate |
| Protein | Biuret Solution | (c) _______________ |
[3]
13. A student places a strip of potato tissue into a concentrated sugar solution.
(a) Predict what will happen to the length of the potato strip after 30 minutes.
[1]
(b) Explain your prediction in terms of water potential and osmosis.
[3]
14. Enzymes are used in biological washing powders to remove stains.
(a) Suggest why biological washing powders are more effective at lower temperatures (e.g., 40°C) compared to non-biological powders.
[2]
(b) Why should biological washing powders not be used at temperatures above 60°C?
[2]
15. The diagram below shows the levels of organisation in a multicellular organism.
Cell → Tissue → Organ → System → Organism
(a) Define the term tissue.
[1]
(b) Give one example of a tissue found in the human digestive system.
[1]
Section C: Free Response Questions (Questions 16–20)
16. Describe the structure of a protein molecule and explain how its structure determines its function as an enzyme.
[4]
17. Explain the importance of maintaining a constant internal body temperature (37°C) for enzyme activity in humans.
[3]
18. A student claims that "All plant cells contain chloroplasts."
Evaluate this statement and provide evidence to support or refute it.
[3]
19. Describe the process of protein synthesis and secretion in a glandular cell, referring to the roles of the nucleus, rough endoplasmic reticulum, and Golgi apparatus.
[5]
20. Discuss the effects of pH on enzyme activity. Include a description of the optimum pH and what happens to the enzyme at extreme pH levels.
[5]
*** End of Quiz ***
Answers
Secondary 3 Biology Quiz - Cells Biomolecules: Answer Key
Section A: Multiple Choice Questions
1. C
Reasoning: Animal cells (like white blood cells) have a nucleus and mitochondria but no cell wall or chloroplasts. Yeast is a fungus (has cell wall). Palisade and root hair cells are plant cells (have cell wall).
2. B
Reasoning: Mitochondria are the site of aerobic respiration. Golgi modifies/packages proteins. Ribosomes synthesize proteins. Nucleus controls cell activities.
3. B
Reasoning: Amino acids are building blocks for proteins. Synthesis starts at ribosomes (on Rough ER), moves to Golgi for modification/packaging, then to vesicles for secretion.
4. C
Reasoning: The absence of a nucleus creates more space for haemoglobin, maximizing oxygen-carrying capacity.
5. C
Reasoning: Enzymes are catalysts and are not destroyed or used up in the reaction; they can be reused.
Section B: Structured Questions
6.
(a) Absorbs light energy for photosynthesis. [1]
(b) The vacuole contains cell sap which exerts turgor pressure against the cell wall. This pressure keeps the cell rigid and maintains the plant's upright shape. [2]
7.
(a) As temperature increases from 20°C to 40°C, the time taken for starch to disappear decreases, indicating that the rate of enzyme activity increases. [2]
(b) At 60°C, the high temperature causes the enzyme (amylase) to denature. The shape of the active site changes, so the substrate (starch) can no longer fit into the active site. No enzyme-substrate complexes are formed, so no digestion occurs. [3]
8.
(a) Absent [1]
(b) Small, temporary vacuoles (or Absent) [1]
(c) Irregular / Round [1]
9.
(a) Mitochondria [1]
(b) Mitochondria are the site of aerobic respiration, which releases energy (ATP). Muscle cells need large amounts of ATP for contraction. [2]
10.
(a) The active site is a specific region on the enzyme surface where the substrate binds. [1]
(b) The enzyme releases the products and remains unchanged, ready to bind with another substrate molecule. [2]
11.
(a) Long hair-like projection (increases surface area). [1]
(b) The large surface area allows for a faster rate of water uptake by osmosis from the soil solution into the cell. [2]
12.
(a) Blue-black [1]
(b) Benedict’s Solution [1]
(c) Purple / Violet [1]
13.
(a) The potato strip will become shorter / flaccid. [1]
(b) The concentrated sugar solution has a lower water potential than the potato cells. Water moves out of the potato cells by osmosis, down the water potential gradient, through the partially permeable cell membrane. Loss of water causes the cells to become flaccid/plasmolysed. [3]
14.
(a) Biological powders contain enzymes that catalyse the breakdown of stains (proteins/fats) at lower temperatures, saving energy compared to heating water to high temperatures for non-biological powders. [2]
(b) High temperatures (above 60°C) will denature the enzymes, changing the shape of their active sites so they can no longer catalyse the reaction. [2]
15.
(a) A group of similar cells working together to perform a specific function. [1]
(b) Epithelial tissue / Muscle tissue / Glandular tissue. [1]
Section C: Free Response Questions
16.
- Proteins are made of long chains of amino acids folded into specific 3D shapes. [1]
- The specific shape of the enzyme, particularly the active site, determines its specificity. [1]
- Only a substrate with a complementary shape can fit into the active site (lock-and-key). [1]
- If the shape changes (denaturation), the enzyme loses its function. [1]
17.
- Human enzymes have an optimum temperature of around 37°C. [1]
- At this temperature, the kinetic energy of molecules is high enough for frequent collisions between enzyme and substrate, maximizing the reaction rate. [1]
- If temperature deviates significantly (too high), enzymes denature; if too low, reaction rates become too slow to sustain life processes. [1]
18.
- The statement is incorrect. [1]
- Evidence: Root hair cells and epidermal cells in roots do not contain chloroplasts because they are underground and do not receive light. [1]
- Chloroplasts are only found in photosynthetic tissues (e.g., palisade mesophyll) exposed to light. [1]
19.
- Nucleus: Contains DNA which codes for the specific protein sequence. mRNA carries this code to the ribosomes. [1]
- Rough Endoplasmic Reticulum (RER): Ribosomes on the RER synthesize the protein using amino acids. The protein enters the lumen of the RER for initial folding/transport. [2]
- Golgi Apparatus: Receives proteins from the RER. Modifies them (e.g., adding carbohydrates), packages them into vesicles, and sorts them for secretion. [2]
20.
- Enzymes have an optimum pH (e.g., pepsin pH 2, amylase pH 7) where they are most active. [1]
- At optimum pH, the charge distribution on the active site allows optimal binding with the substrate. [1]
- At extreme pH levels (too acidic or too alkaline), the bonds holding the enzyme's 3D structure are broken. [1]
- This causes the enzyme to denature, changing the shape of the active site. [1]
- The substrate can no longer fit, and the rate of reaction drops to zero. [1]