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Secondary 4 Pure Biology Cells Biomolecules Quiz
Free Exam-Derived Secondary 4 Pure Biology Cells Biomolecules quiz with questions and answers for Singapore students. This page is rendered as a direct URL so the questions and answers can be discovered without pressing in-page buttons.
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Questions
Secondary 4 Pure Biology Quiz - Cells Biomolecules
Name: _________________ Class: _______ Date: _________
Score: _____ / 35 Duration: 45 minutes
Instructions:
- Answer ALL questions in the spaces provided
- Show all working for calculations
- Use appropriate biological terminology
Section A: Short Answer Questions [15 marks]
1. Name the cells through which water is absorbed from the soil. [1]
2. State the chemical elements present in proteins. [2]
3. Define diffusion. [2]
4. Name the enzyme that breaks down starch into maltose. [1]
5. State two functions of the cell membrane. [2]
6. Complete the word equation for aerobic respiration. [3]
glucose + _________________ → _________________ + _________________ + energy
7. Name the organelle where photosynthesis occurs in plant cells. [1]
8. State three factors that affect the rate of enzyme activity. [3]
Section B: Structured Questions [20 marks]
9. The diagram shows an electron micrograph of a plant cell.
[Diagram shows a plant cell with structures labeled A, B, C, D, E representing nucleus, chloroplast, mitochondrion, cell wall, and vacuole respectively]
(a) Which labeled structure is the site of protein synthesis? [1]
(b) Explain why structure B is not found in animal cells. [2]
(c) State the function of structure E in maintaining cell shape. [2]
10. A student investigated the effect of temperature on enzyme activity using amylase and starch.
The results are shown in the table below:
| Temperature (°C) | Time for starch to disappear (minutes) |
|---|---|
| 20 | 15 |
| 30 | 8 |
| 40 | 4 |
| 50 | 2 |
| 60 | 6 |
| 70 | No reaction |
(a) At which temperature was enzyme activity highest? Explain your answer. [2]
(b) Explain why no reaction occurred at 70°C. [3]
(c) Suggest one variable that should be kept constant in this investigation. [1]
11. The diagram shows three plant cells in solutions of different concentrations.
[Diagram shows three cells: Cell X in distilled water (turgid), Cell Y in 0.5M sucrose (normal), Cell Z in 1.0M sucrose (plasmolyzed)]
(a) In which direction will water move by osmosis in Cell X? Explain your answer. [3]
(b) Describe what has happened to Cell Z and explain why. [3]
(c) State the term used to describe the condition of Cell X. [1]
(d) Explain why animal cells would be damaged in the solution surrounding Cell X. [2]
Answers
Secondary 4 Pure Biology Quiz - Cells Biomolecules - Answer Key
Section A: Short Answer Questions [15 marks]
1. Name the cells through which water is absorbed from the soil. [1] Answer: Root hair cells Marking: 1 mark for "root hair cells" (accept "root hair cell")
2. State the chemical elements present in proteins. [2] Answer: Carbon, hydrogen, oxygen, nitrogen (and sulfur) Marking: 1 mark for each correct element, maximum 2 marks. Must include C, H, O, N for full marks.
3. Define diffusion. [2] Answer: The net movement of particles from a region of high concentration to a region of low concentration down a concentration gradient. Marking: 1 mark for "movement of particles", 1 mark for "from high to low concentration" or "down concentration gradient"
4. Name the enzyme that breaks down starch into maltose. [1] Answer: Amylase Marking: 1 mark for "amylase"
5. State two functions of the cell membrane. [2] Answer: Any two from: Controls entry and exit of substances / Partially permeable / Maintains cell shape / Site of chemical reactions / Recognition of other cells Marking: 1 mark for each correct function, maximum 2 marks
6. Complete the word equation for aerobic respiration. [3] Answer: glucose + oxygen → carbon dioxide + water + energy Marking: 1 mark for each correct product (oxygen, carbon dioxide, water)
7. Name the organelle where photosynthesis occurs in plant cells. [1] Answer: Chloroplast Marking: 1 mark for "chloroplast"
8. State three factors that affect the rate of enzyme activity. [3] Answer: Temperature, pH, enzyme concentration, substrate concentration Marking: 1 mark for each correct factor, maximum 3 marks
Section B: Structured Questions [20 marks]
9(a) Which labeled structure is the site of protein synthesis? [1] Answer: None of the labeled structures (ribosomes not shown/labeled) Marking: 1 mark for recognizing ribosomes are not labeled, or stating "ribosomes" if that was an option
9(b) Explain why structure B is not found in animal cells. [2] Answer: Structure B is a chloroplast. Animal cells do not carry out photosynthesis / Animal cells do not need to make their own food. Marking: 1 mark for identifying chloroplast, 1 mark for explanation
9(c) State the function of structure E in maintaining cell shape. [2] Answer: Structure E is the vacuole. It maintains turgor pressure by being filled with cell sap, which pushes against the cell wall to keep the cell rigid. Marking: 1 mark for turgor pressure, 1 mark for explanation of mechanism
10(a) At which temperature was enzyme activity highest? Explain your answer. [2] Answer: 50°C. This is where the reaction was fastest (shortest time for starch to disappear). Marking: 1 mark for 50°C, 1 mark for explanation
10(b) Explain why no reaction occurred at 70°C. [3] Answer: The high temperature denatured the enzyme. The active site changed shape so the substrate could no longer bind to the enzyme. Marking: 1 mark for "denatured", 1 mark for "active site changed shape", 1 mark for "substrate cannot bind"
10(c) Suggest one variable that should be kept constant in this investigation. [1] Answer: Any one from: pH, enzyme concentration, substrate concentration, volume of solutions Marking: 1 mark for any appropriate variable
11(a) In which direction will water move by osmosis in Cell X? Explain your answer. [3] Answer: Water will move into the cell. The cell has a lower water potential than the distilled water, so water moves down the water potential gradient into the cell. Marking: 1 mark for "into the cell", 1 mark for "lower water potential", 1 mark for "down water potential gradient"
11(b) Describe what has happened to Cell Z and explain why. [3] Answer: The cell has become plasmolyzed. Water has moved out of the cell by osmosis because the external solution has a lower water potential than the cell contents. Marking: 1 mark for "plasmolyzed", 1 mark for "water moved out", 1 mark for explanation of water potential gradient
11(c) State the term used to describe the condition of Cell X. [1] Answer: Turgid Marking: 1 mark for "turgid"
11(d) Explain why animal cells would be damaged in the solution surrounding Cell X. [2] Answer: Animal cells do not have a cell wall. Water would enter by osmosis and the cell would swell and burst (lyse). Marking: 1 mark for "no cell wall", 1 mark for "cell would burst/lyse"