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O Level Biology Cells Biomolecules Quiz
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Questions
O-Level Biology Quiz - Cells Biomolecules
Name: __________________________
Class: __________________________
Date: __________________________
Score: ________ / 40
Duration: 45 minutes
Total Marks: 40
Instructions:
- Answer all questions in the spaces provided.
- The number of marks is indicated in brackets [ ] at the end of each question or part question.
- Use black or blue ink. Draw diagrams in pencil.
- This quiz covers Topic 1 (Cell Structure), Topic 2 (Movement of Substances), and Topic 3 (Biological Molecules).
Section A: Multiple Choice (Questions 1–5)
Choose the correct answer and write the letter in the box provided.
1. Which structure is found in a plant cell but not in an animal cell?
A. Cell membrane
B. Cytoplasm
C. Mitochondrion
D. Cell wall
Answer: [ ] [1]
2. A student observes a cell under a light microscope. The cell has a nucleus, cytoplasm, and a cell membrane, but no cell wall. It is irregular in shape. What type of cell is this likely to be?
A. Palisade mesophyll cell
B. Red blood cell
C. Cheek epithelial cell
D. Root hair cell
Answer: [ ] [1]
3. Which row correctly describes the movement of molecules during osmosis?
| Direction of Movement | Membrane Type | Energy Required? | |
|---|---|---|---|
| A | High to low water potential | Partially permeable | No |
| B | Low to high water potential | Fully permeable | Yes |
| C | High to low concentration | Partially permeable | Yes |
| D | Low to high concentration | Fully permeable | No |
Answer: [ ] [1]
4. An enzyme is heated to 80°C. What happens to the enzyme?
A. It works faster because the particles have more kinetic energy.
B. It is denatured because the shape of the active site changes.
C. It is killed because enzymes are living organisms.
D. It remains unchanged because enzymes are heat-resistant.
Answer: [ ] [1]
5. Which food test result indicates the presence of protein?
A. Benedict’s solution turns brick-red.
B. Iodine solution turns blue-black.
C. Biuret solution turns purple.
D. Ethanol emulsion test turns cloudy white.
Answer: [ ] [1]
Section B: Structured Questions (Questions 6–15)
6. The diagram below represents a simplified animal cell.
(Imagine a diagram with labels A, B, and C pointing to the Nucleus, Cell Membrane, and Mitochondrion respectively.)
(a) Identify the structures labelled A, B, and C.
A: __________________________
B: __________________________
C: __________________________
[3]
(b) State one function of structure C.
[1]
7. Define the term active transport.
[2]
8. Explain why root hair cells contain many mitochondria.
[2]
9. A student places a strip of potato tissue in a concentrated sugar solution. After 30 minutes, the potato strip becomes flaccid (soft).
(a) Explain why the potato strip became flaccid.
[3]
(b) Name the process responsible for this change.
[1]
10. The table below shows the results of food tests performed on Solution X.
| Test | Reagent Used | Result |
|---|---|---|
| 1 | Iodine Solution | Blue-Black |
| 2 | Benedict’s Solution (heated) | Blue (No change) |
| 3 | Biuret Solution | Blue (No change) |
(a) Which biological molecule is present in Solution X?
[1]
(b) Which biological molecule is definitely absent from Solution X?
[1]
(c) Why was the Benedict’s test heated?
[1]
11. Enzymes are biological catalysts.
(a) What is meant by the term catalyst?
[1]
(b) Explain the lock and key hypothesis of enzyme action.
[3]
12. The graph below shows the effect of pH on the activity of two enzymes, Pepsin and Trypsin.
(Imagine a graph: Pepsin peaks at pH 2, Trypsin peaks at pH 8.)
(a) What is the optimum pH for Pepsin?
[1]
(b) In which part of the human digestive system would you expect to find Pepsin?
[1]
(c) Explain what happens to the enzyme Trypsin if the pH is changed from 8 to 2.
[2]
13. Compare the structure of a bacterial cell and an animal cell. State two differences.
[2]
14. Glucose is a small molecule that can enter cells by diffusion. Starch is a large molecule that cannot.
(a) Starch is a polymer. Name the monomer unit that makes up starch.
[1]
(b) Why can starch not pass through the cell membrane by diffusion?
[1]
15. Describe the role of the Golgi body in a cell.
[2]
Section C: Free Response / Data Analysis (Questions 16–20)
16. A student investigates the effect of temperature on the rate of reaction of the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen.
The volume of oxygen produced in 1 minute was measured at different temperatures.
| Temperature (°C) | Volume of Oxygen (cm³) |
|---|---|
| 10 | 5 |
| 20 | 12 |
| 30 | 25 |
| 40 | 30 |
| 50 | 10 |
| 60 | 0 |
(a) Plot a line graph of these results on the grid provided below.
(Student to sketch axes: X-axis Temp, Y-axis Volume. Draw curve.)
[3]
(b) Explain the shape of the graph between 10°C and 40°C.
[3]
(c) Explain why no oxygen was produced at 60°C.
[2]
17. Red blood cells are specialised for their function.
(a) State the function of red blood cells.
[1]
(b) Describe two structural adaptations of red blood cells that help them perform this function.
[2]
18. A plant cell is placed in pure water.
(a) Describe what happens to the cell.
[1]
(b) Explain why the cell does not burst.
[2]
19. Proteins are made of amino acids.
(a) Name the chemical elements found in all amino acids.
[1]
(b) State one function of proteins in the human body other than growth and repair.
[1]
20. Explain why enzymes are described as specific.
[2]
End of Quiz
Answers
O-Level Biology Quiz - Cells Biomolecules (Answer Key)
Total Marks: 40
Section A: Multiple Choice
1. D
Explanation: Plant cells have cell walls, chloroplasts, and large vacuoles. Animal cells do not. Both have membranes, cytoplasm, and mitochondria. [1]
2. C
Explanation: Cheek cells are animal cells (no wall, irregular shape). Palisade and root hair cells are plant cells. Red blood cells are animal cells but are biconcave discs, not typically described as "irregular" in this context, and lack a nucleus (which the prompt implies is present). [1]
3. A
Explanation: Osmosis is the net movement of water molecules from a region of higher water potential to lower water potential, through a partially permeable membrane, without energy. [1]
4. B
Explanation: High temperatures break bonds holding the enzyme structure, changing the active site shape (denaturation). Enzymes are not alive, so they cannot be "killed". [1]
5. C
Explanation: Biuret solution turns purple in the presence of protein. Benedict's is for reducing sugars, Iodine for starch, Ethanol for fats. [1]
Section B: Structured Questions
6.
(a) A: Nucleus [1], B: Cell Membrane [1], C: Mitochondrion [1]
(b) Site of aerobic respiration / produces energy (ATP). [1]
7.
The movement of substances/ions/molecules [1] from a region of lower concentration to a region of higher concentration (against the concentration gradient) [1], using energy (ATP). [1] (Max 2 marks)
8.
Root hair cells absorb mineral ions by active transport [1]. Active transport requires energy (ATP), which is produced by mitochondria during respiration. [1]
9.
(a) The sugar solution has a lower water potential (higher solute concentration) than the potato cell sap [1]. Water moves out of the potato cells by osmosis [1]. The cells lose turgor pressure and become flaccid. [1]
(b) Osmosis. [1]
10.
(a) Starch. [1]
(b) Reducing sugar (or Protein). [Accept either, as both tests were negative] [1]
(c) Benedict’s test requires heat energy to allow the reaction between the reducing sugar and the copper ions to occur. [1]
11.
(a) A substance that speeds up the rate of a chemical reaction [1] without being used up/changed itself. [1] (Max 1 mark for definition)
(b) The substrate has a specific shape [1] that fits into the enzyme’s active site [1], like a key fits into a lock. This forms an enzyme-substrate complex. [1]
12.
(a) pH 2. [1]
(b) Stomach. [1]
(c) The enzyme becomes denatured [1]. The change in pH alters the shape of the active site, so the substrate can no longer bind. [1]
13.
Any two of the following:
- Bacterial cells have no nucleus (have nucleoid); Animal cells have a nucleus. [1]
- Bacterial cells have a cell wall (peptidoglycan); Animal cells have no cell wall. [1]
- Bacterial cells have plasmids; Animal cells do not. [1]
- Bacterial ribosomes are smaller (70S) than animal ribosomes (80S). [1]
14.
(a) Glucose. [1]
(b) Starch molecules are too large to pass through the pores of the cell membrane. [1]
15.
Modifies, sorts, and packages proteins [1] for secretion or transport within the cell. [1]
Section C: Free Response / Data Analysis
16.
(a) Graph Marks:
- Axes labelled correctly (Temperature / °C and Volume / cm³) [1]
- Scale is linear and appropriate [1]
- Points plotted correctly and joined with a smooth curve (bell-shaped) [1]
(b) As temperature increases, the kinetic energy of enzyme and substrate molecules increases [1]. This leads to more frequent collisions [1] and more enzyme-substrate complexes forming, increasing the rate of reaction. [1]
(c) At 60°C, the enzyme is denatured [1]. The active site has changed shape permanently, so the substrate cannot bind, and no reaction occurs. [1]
17.
(a) To transport oxygen. [1]
(b) Any two:
- Biconcave shape increases surface area for gas exchange. [1]
- No nucleus allows more space for haemoglobin/oxygen. [1]
- Contains haemoglobin to bind oxygen. [1]
- Thin membrane for short diffusion distance. [1]
18.
(a) The cell becomes turgid (swells). [1]
(b) The cell wall is strong and rigid [1]. It exerts wall pressure that prevents the cell from bursting when water enters by osmosis. [1]
19.
(a) Carbon, Hydrogen, Oxygen, Nitrogen. [1] (Must include Nitrogen)
(b) Enzymes / Hormones / Antibodies / Transport (Haemoglobin). [1] (Any one)
20.
Each enzyme has a unique active site shape [1]. Only a substrate with a complementary shape can fit into this active site [1]. Therefore, each enzyme catalyses only one specific reaction. [1] (Max 2 marks)