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O Level Biology Cells Biomolecules Quiz
Free O Level Biology Cells Biomolecules quiz, Exam version, with questions, answers, and O Level-style practice for Singapore students.
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O-Level Biology Quiz - Cells Biomolecules - Answer Key
Total Marks: 25
Section A: Short Answer Questions [8 marks]
1. Name the process by which water moves across a partially permeable membrane. [1]
Answer: Osmosis [1]
2. State the chemical elements present in proteins. [1]
Answer: Carbon, Hydrogen, Oxygen, Nitrogen (sometimes Sulfur) [1] Note: Accept C, H, O, N or full names
3. Complete the word equation for aerobic respiration: [2]
Answer: Glucose + Oxygen → Carbon dioxide + Water + Energy [2] Award 1 mark for each correct term
4. Name two organelles that are visible under an electron microscope but not under a light microscope. [2]
Answer: Any two from:
- Endoplasmic reticulum [1]
- Golgi body/apparatus [1]
- Ribosomes [1]
- Mitochondria (inner structure) [1]
5. State the equation for anaerobic respiration in humans. [2]
Answer: Glucose → Lactate + Energy [2] Alternative: C₆H₁₂O₆ → 2C₃H₆O₃ + Energy Award 1 mark for glucose, 1 mark for lactate/lactic acid
Section B: Structured Response Questions [17 marks]
6. Organelle identification [2]
(a) Which organelle carries out photosynthesis? [1] Answer: Letter corresponding to chloroplast [1]
(b) Which organelle synthesises and transports proteins? [1] Answer: Letter corresponding to rough endoplasmic reticulum [1]
7. Describe two features of a bacterial cell that are different from an animal cell. [2]
Marking scheme:
- Cell wall made of peptidoglycan vs no cell wall [1]
- Plasmids present vs absent [1]
- Nucleoid vs membrane-bound nucleus [1]
- 70S ribosomes vs 80S ribosomes [1]
- Flagella present vs absent [1] Award any 2 correct differences
8. Explain how changes in a person's protein intake can affect the concentration of their urine. [3]
Marking scheme:
- Increased protein intake leads to increased amino acid deamination [1]
- This produces more urea in the blood [1]
- More urea increases solute concentration, so more water is reabsorbed by osmosis, making urine more concentrated [1]
9. Describe the roles of enzymes in human digestion. Give examples in your answers. [4]
Marking scheme:
- Enzymes act as biological catalysts to speed up digestion [1]
- Named enzyme + substrate (e.g., amylase acts on starch) [1]
- Product or location (e.g., producing maltose in mouth/small intestine) [1]
- Second example with enzyme + substrate/product [1]
Examples: amylase→starch→maltose; pepsin→proteins→polypeptides; lipase→fats→fatty acids and glycerol
10. Enzyme activity investigation [5]
(a) State the optimum temperature for this enzyme. [1] Answer: 37°C [1]
(b) Explain why enzyme activity decreases above the optimum temperature. [2] Marking scheme:
- High temperature causes enzyme to denature [1]
- Active site changes shape, so enzyme-substrate complex cannot form [1]
(c) Suggest why this enzyme has an optimum temperature of 37°C. [2] Marking scheme:
- 37°C is human body temperature [1]
- Enzyme is adapted to work efficiently at normal body temperature [1]