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Secondary 3 Biology Practice Paper 1
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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 is indicated in brackets [ ] at the end of each question or part question.
- This quiz covers Cell Structure, Movement of Substances, and Biological Molecules (Enzymes).
Section A: Multiple Choice Questions (Questions 1–5)
Choose the correct answer and write the letter in the box provided.
1. Which of the following structures is found in a typical plant cell but not in a typical animal cell?
A. Cell membrane
B. Cytoplasm
C. Mitochondrion
D. Cell wall
Answer: [____] [1]
2. A student observes a cell under an electron microscope. The cell contains many mitochondria and extensive rough endoplasmic reticulum (RER). What is the most likely function of this cell?
A. Storage of starch
B. Synthesis and secretion of proteins
C. Absorption of water
D. Contraction for movement
Answer: [____] [1]
3. Which row correctly describes the movement of oxygen and glucose into a cell?
| Oxygen | Glucose (in small intestine villi) | |
|---|---|---|
| A | Diffusion | Diffusion |
| B | Diffusion | Active Transport |
| C | Osmosis | Active Transport |
| D | Active Transport | Diffusion |
Answer: [____] [1]
4. An enzyme is heated to 80°C and then cooled to its optimum temperature of 37°C. The enzyme does not function. Why?
A. The enzyme has been denatured.
B. The substrate has been denatured.
C. The kinetic energy of the molecules is too low.
D. The active site has become more flexible.
Answer: [____] [1]
5. Which test and result correctly identifies the presence of protein in a food sample?
A. Benedict’s solution → Brick-red precipitate
B. Iodine solution → Blue-black colour
C. Biuret solution → Purple/Violet colour
D. Ethanol emulsion test → Cloudy white emulsion
Answer: [____] [1]
Section B: Structured Questions (Questions 6–15)
6. Fig 6.1 shows a diagram of a specialised cell.
(Imagine a diagram of a Red Blood Cell: biconcave disc shape, no nucleus)
(a) Identify this cell.
_________________________________________________________________________ [1]
(b) State two structural adaptations of this cell that help it perform its function.
-
- _______________________________________________________________________ [2]
(c) Explain why this cell cannot undergo mitosis.
_________________________________________________________________________ [1]
7. A student investigates the effect of temperature on the activity of the enzyme amylase. The student mixes starch solution with amylase at different temperatures and records the time taken for the starch to disappear.
(a) Define the term enzyme.
_________________________________________________________________________ [2]
(b) Explain why the rate of reaction increases as the temperature rises from 10°C to 40°C.
_________________________________________________________________________ [2]
(c) At 70°C, the reaction stops completely. Explain why.
_________________________________________________________________________ [2]
8. Fig 8.1 shows a setup to investigate osmosis. A visking tubing bag containing concentrated sugar solution is placed in a beaker of distilled water.
(a) Define osmosis.
_________________________________________________________________________ [2]
(b) After 30 minutes, the level of liquid in the tubing rises. Explain why.
_________________________________________________________________________ [3]
(c) If the distilled water in the beaker was replaced with a sugar solution of the same concentration as inside the tubing, what would happen to the liquid level? Explain your answer.
_________________________________________________________________________ [2]
9. Compare diffusion and active transport.
(a) State one similarity between diffusion and active transport.
_________________________________________________________________________ [1]
(b) State two differences between diffusion and active transport.
-
- _______________________________________________________________________ [2]
10. Biological molecules are made of smaller units.
(a) Complete the table below.
| Biological Molecule | Basic Unit (Monomer) | Chemical Elements Present |
|---|---|---|
| Starch | Glucose | C, H, O |
| Protein | __________________ | C, H, O, N |
| Fat (Lipid) | Glycerol and _______________ | C, H, O |
[3]
(b) Describe how you would test a sample of milk for the presence of reducing sugars. Include the reagent used and the positive result.
_________________________________________________________________________ [3]
11. Fig 11.1 shows an animal cell and a plant cell.
(a) Label the following structures on the diagrams (assume labels A, B, C are pointing to Nucleus, Chloroplast, Cell Membrane):
A: __________________________
B: __________________________
C: __________________________ [3]
(b) State the function of the structure labelled B.
_________________________________________________________________________ [1]
12. Root hair cells are specialised for absorption.
(a) Explain how the shape of a root hair cell increases the efficiency of water uptake.
_________________________________________________________________________ [2]
(b) Water enters root hair cells by osmosis. Ion uptake (e.g., nitrates) often occurs by active transport. Why is active transport necessary for ion uptake from soil water?
_________________________________________________________________________ [2]
13. Enzymes are specific in their action.
(a) Explain the lock-and-key hypothesis of enzyme action.
_________________________________________________________________________ [3]
(b) Why is enzyme specificity important for metabolic processes in the body?
_________________________________________________________________________ [1]
14. A student performs the Ethanol Emulsion Test for fats.
(a) Describe the steps involved in this test.
_________________________________________________________________________ [2]
(b) What constitutes a positive result?
_________________________________________________________________________ [1]
15. Fig 15.1 shows a graph of the rate of an enzyme-controlled reaction against pH. The optimum pH is 7.
(a) Sketch the expected shape of the curve if the enzyme was pepsin (found in the stomach, optimum pH 2).
(Describe the sketch: Peak at pH 2, low/zero activity at pH 7)
_________________________________________________________________________ [2]
(b) Explain why pepsin would not function effectively in the small intestine (pH 8).
_________________________________________________________________________ [2]
Section C: Free Response Questions (Questions 16–20)
16. Explain the importance of mitochondria in muscle cells compared to skin cells.
_________________________________________________________________________ [2]
17. Distinguish between organic and inorganic molecules, giving one example of each found in living organisms.
_________________________________________________________________________ [2]
18. Describe the effect of placing a plant cell in a hypertonic (very salty) solution. Use the terms plasmolysis, cell wall, and vacuole in your answer.
_________________________________________________________________________ [3]
19. Why is it incorrect to say that "enzymes are used up" in a reaction?
_________________________________________________________________________ [2]
20. A patient has a genetic condition where their cells lack functional lysosomes. Suggest why this might lead to a buildup of waste materials in the cell.
_________________________________________________________________________ [2]
End of Quiz
Answers
Secondary 3 Biology Quiz - Cells Biomolecules (Answer Key)
Total Marks: 40
Section A: Multiple Choice Answers
1. D
Reasoning: Cell walls are present in plant cells but absent in animal cells. Cell membranes, cytoplasm, and mitochondria are found in both.
2. B
Reasoning: Rough Endoplasmic Reticulum (RER) is involved in protein synthesis, and mitochondria provide the energy required for synthesis and secretion.
3. B
Reasoning: Oxygen moves by diffusion down its concentration gradient. Glucose absorption in the villi often involves active transport to move against the concentration gradient into the blood.
4. A
Reasoning: High temperatures break the bonds holding the enzyme's structure, changing the shape of the active site (denaturation). This is irreversible.
5. C
Reasoning: Biuret solution turns purple/violet in the presence of protein. Benedict’s is for reducing sugars, Iodine for starch, Ethanol for fats.
Section B: Structured Answers
6.
(a) Red Blood Cell (Erythrocyte) [1]
(b) Any two of: [2]
- Biconcave shape: Increases surface area for faster diffusion of oxygen.
- No nucleus: Provides more space for haemoglobin to carry oxygen.
- Thin cell membrane: Shortens diffusion distance for oxygen.
(c) It lacks a nucleus (and therefore DNA/chromosomes), which is required for cell division/mitosis. [1]
7.
(a) An enzyme is a biological catalyst [1] made of protein [1] that speeds up chemical reactions without being used up. [2]
(b) As temperature increases, kinetic energy of enzyme and substrate molecules increases [1]. This leads to more frequent and successful collisions between the substrate and the active site [1]. [2]
(c) The high temperature breaks the hydrogen bonds holding the enzyme's tertiary structure [1]. The active site changes shape and is no longer complementary to the substrate [1]. The enzyme is denatured [1]. [3]
(Note: Accept 2 marks for clear explanation of denaturation)
8.
(a) Osmosis is the net movement of water molecules [1] from a region of higher water potential to a region of lower water potential [1] through a partially permeable membrane. [2]
(b) The sugar solution inside the tubing has a lower water potential than the distilled water outside [1]. Water molecules move into the tubing by osmosis [1]. This increases the volume/pressure inside the tubing, causing the liquid level to rise [1]. [3]
(c) The liquid level would remain unchanged (stay the same) [1]. There is no water potential gradient (concentrations are equal), so there is no net movement of water [1]. [2]
9.
(a) Both involve the movement of substances across a cell membrane. [1]
(b) Any two differences: [2]
- Diffusion does not require energy (passive); Active transport requires energy (ATP).
- Diffusion moves substances down a concentration gradient; Active transport moves substances against a concentration gradient.
- Diffusion involves small molecules/ions; Active transport often involves ions or larger molecules.
10.
(a) [3]
- Protein Basic Unit: Amino Acids
- Fat Basic Unit: Fatty Acids
- Protein Elements: (Already given as C,H,O,N - correct)
(Note: Student must fill in "Amino Acids" and "Fatty Acids")
(b) Add Benedict’s solution to the milk sample [1]. Heat the mixture in a water bath (boil) [1]. A positive result is a colour change from blue to green/yellow/orange/brick-red precipitate [1]. [3]
11.
(a) A: Nucleus, B: Chloroplast, C: Cell Membrane [3]
(b) Chloroplasts contain chlorophyll and are the site of photosynthesis, where light energy is converted to chemical energy (glucose). [1]
12.
(a) The long hair-like projection increases the surface area to volume ratio [1], allowing for a faster rate of water absorption by osmosis [1]. [2]
(b) The concentration of ions in the soil water is often lower than inside the root hair cell [1]. Therefore, ions must be moved against the concentration gradient, which requires energy (active transport) [1]. [2]
13.
(a) The substrate has a specific shape that fits into the enzyme's active site [1], like a key fits into a lock [1]. This forms an enzyme-substrate complex [1], leading to the reaction. [3]
(b) It ensures that specific reactions occur at the right time and place, preventing unwanted side reactions and maintaining metabolic order. [1]
14.
(a) Mix the food sample with ethanol (alcohol) and shake [1]. Pour the solution into water [1]. [2]
(b) Formation of a cloudy white emulsion. [1]
15.
(a) The curve should peak at pH 2 and drop to zero (or very low) activity by pH 7. [2]
(b) Pepsin is adapted to work in acidic conditions. At pH 8 (alkaline), the enzyme will be denatured [1] because the change in pH affects the bonds holding the active site shape [1]. [2]
Section C: Free Response Answers
16.
Muscle cells require large amounts of energy (ATP) for contraction [1]. Mitochondria are the site of aerobic respiration, which releases energy [1]. Skin cells have lower energy demands, so they have fewer mitochondria. [2]
17.
Organic molecules contain carbon-hydrogen (C-H) bonds and are usually complex (e.g., Glucose, Protein) [1]. Inorganic molecules generally do not contain C-H bonds and are simpler (e.g., Water, Carbon Dioxide, Salts) [1]. [2]
18.
Water leaves the cell by osmosis because the external solution has a lower water potential [1]. The vacuole shrinks [1]. The cytoplasm pulls away from the cell wall [1]. This process is called plasmolysis. The cell wall remains rigid, but the cell becomes flaccid. [3]
19.
Enzymes are catalysts [1]. They lower the activation energy but are not chemically changed or consumed in the reaction [1]. They can be reused multiple times. [2]
20.
Lysosomes contain digestive enzymes [1]. These enzymes break down waste materials, old organelles, and ingested particles [1]. Without functional lysosomes, these materials accumulate and cannot be recycled or removed, potentially damaging the cell [1]. [2]