A Level H2 Biology Cells Biomolecules Quiz

A-Level Biology H2 Quiz - Cells Biomolecules - Answer Key

Section A: Short Answer Questions [15 marks]

1. State the role of ATP in cellular processes. [2]

• Provides energy for metabolic reactions / energy currency of the cell [1]
• Phosphorylates other molecules to make them more reactive [1]

2. Name the two main types of nucleic acids found in cells. [2]

• DNA (deoxyribonucleic acid) [1]
• RNA (ribonucleic acid) [1]

3. Explain why enzymes are described as specific. [2]

• Active site has complementary shape to substrate [1]
• Only specific substrate(s) can bind to form enzyme-substrate complex [1]

4. State two differences between prokaryotic and eukaryotic ribosomes. [2] Any two from:

• Prokaryotic ribosomes are 70S, eukaryotic are 80S [1]
• Prokaryotic ribosomes are smaller [1]
• Prokaryotic ribosomes are free in cytoplasm, eukaryotic can be bound to ER [1]

5. Define the term 'amphipathic' as applied to phospholipids. [2]

• Having both hydrophilic and hydrophobic regions [1]
• Hydrophilic phosphate head and hydrophobic fatty acid tails [1]

6. Name the process by which glucose molecules are joined to form starch. [1]

• Condensation (reaction) [1]

7. State four functions of proteins in living organisms. [4] Any four from:

• Enzymes / catalysis [1]
• Structural (e.g., collagen, keratin) [1]
• Transport (e.g., haemoglobin, channel proteins) [1]
• Hormones (e.g., insulin) [1]
• Antibodies / immune function [1]
• Movement (e.g., actin, myosin) [1]

Section B: Structured Questions [20 marks]

8.(a) Identify the structures labelled A, B, C and D. [4] A: Outer membrane [1] B: Inner membrane [1] C: Cristae [1] D: Matrix [1]

8.(b) With reference to Fig. 8.1, explain how the structure of the mitochondrion is adapted for its role in aerobic respiration. [4]

• Inner membrane folded into cristae increases surface area [1]
• For electron transport chain and ATP synthesis [1]
• Matrix contains enzymes for Krebs cycle [1]
• Double membrane allows compartmentalization / proton gradient formation [1]

9.(a) Describe how you would extract catalase from potato tissue. [3]

• Chop/blend potato tissue to break cell walls [1]
• Add buffer solution to maintain pH [1]
• Filter to remove cell debris / centrifuge and collect supernatant [1]

9.(b) The student measured the rate of oxygen production at different temperatures. Explain why oxygen production is a suitable measure of catalase activity. [2]

• Catalase breaks down hydrogen peroxide [1]
• Producing oxygen and water, so oxygen production indicates enzyme activity [1]

9.(c) Predict and explain the effect of increasing temperature from 20°C to 60°C on catalase activity. [4]

• Initially activity increases with temperature [1]
• Due to increased kinetic energy / more enzyme-substrate collisions [1]
• Activity decreases at high temperatures (around 40-50°C) [1]
• Due to enzyme denaturation / loss of active site shape [1]

10. Describe the structure and function of the cell surface membrane. [3]

• Phospholipid bilayer with embedded proteins [1]
• Controls entry and exit of substances / selective permeability [1]
• Maintains cell shape / provides barrier between cell and environment [1]