A Level H1 Biology Cells Biomolecules Quiz

A-Level Biology H1 Quiz - Cells Biomolecules (Answer Key)

Total Marks: 40
Topic: Cells & Biomolecules (Core Idea 1, 8876 H1 Biology)

Section A: Cell Structures and Organelles

Q1. [2 marks]

• Answer: Structure X is the centriole (pair). Function: involved in organisation of spindle fibres during cell division (mitosis).
• Teaching note: Centrioles are small cylindrical structures near the nucleus in animal cells. They help separate chromosomes.
• Mark breakdown: 1 mark name, 1 mark function.
• Common mistake: Calling it "centrosome" (centrosome includes centrioles plus matrix).

Q2. [3 marks]

• Answer: Bacterial cell has: (1) circular DNA (not linear, no nucleus); (2) 70S ribosomes (smaller than eukaryotic 80S); (3) peptidoglycan cell wall; lacks membrane-bound organelles.
• Teaching note: Prokaryotes differ from eukaryotes in genetic material shape and ribosome size.
• Mark breakdown: 1 mark circular DNA, 1 mark 70S ribosomes, 1 mark peptidoglycan wall / no membrane-bound organelles.

Q3. [2 marks]

• Answer: Golgi body modifies, sorts, and packages proteins (e.g., enzymes) from rough ER into secretory vesicles for release from liver cell.
• Teaching note: In liver cells, Golgi processes proteins for secretion.
• Mark breakdown: 1 mark modify/packaging, 1 mark secretion/vesicles.

Q4. [2 marks]

• Answer: (1) Cell is the smallest unit of life; (2) all cells arise from pre-existing cells; (3) living organisms are composed of cells (any two).
• Teaching note: Cell theory foundational to biology.
• Mark breakdown: 1 mark each point.

Q5. [3 marks]

• Answer: Mitochondria have outer and inner membranes. Inner membrane folded into cristae → large surface area for electron transport chain and ATP synthase; matrix for Krebs cycle.
• Teaching note: Double membrane separates compartments for chemiosmosis.
• Mark breakdown: 1 mark double membrane, 1 mark cristae/surface area, 1 mark ATP synthesis link.

Section B: Biomolecules and Membranes

Q6. [2 marks]

• Answer: Phospholipids form a bilayer; hydrophilic heads face outward to aqueous environments, hydrophobic tails face inward away from water.
• Teaching note: This gives membrane selectivity.
• Mark breakdown: 1 mark bilayer, 1 mark head/tail orientation.

Q7. [2 marks]

• Answer: Glycosidic bond formed; water molecule released (condensation reaction).
• Teaching note: α-glucose + α-glucose → maltose + H₂O.
• Mark breakdown: 1 mark bond name, 1 mark water.

Q8. [3 marks]

• Answer: Phospholipid: glycerol + 2 fatty acids + phosphate group. Triglyceride: glycerol + 3 fatty acids. Phospholipid has phosphate instead of third fatty acid → amphipathic.
• Teaching note: Difference allows membrane formation.
• Mark breakdown: 1 mark phospholipid 2 FA + phosphate, 1 mark triglyceride 3 FA, 1 mark comparison.

Q9. [3 marks]

• Answer: Cellulose is β-glucose polymer with straight chains; hydrogen bonds between chains form microfibrils → strong, rigid wall.
• Teaching note: β(1→4) linkages give straight structure.
• Mark breakdown: 1 mark β-glucose/straight, 1 mark H-bonds, 1 mark strength/role.

Q10. [2 marks]

• Answer: Cholesterol reduces membrane fluidity at high temp and prevents crystallisation at low temp; maintains stability.
• Teaching note: Fits between phospholipids.
• Mark breakdown: 1 mark temp buffer, 1 mark stability.

Section C: Transport and Proteins

Q11. [3 marks]

• Answer: Glucose binds carrier protein; moves down concentration gradient from blood (high) to cytoplasm (low) via conformational change; no ATP needed.
• Teaching note: Facilitated diffusion is passive.
• Mark breakdown: 1 mark carrier, 1 mark gradient, 1 mark no ATP/passive.

Q12. [3 marks]

• Answer: Active transport uses ATP to move against gradient; osmosis is passive water movement across semi-permeable membrane down water potential gradient.
• Teaching note: Both membrane processes but energy differs.
• Mark breakdown: 1 mark active+ATP, 1 mark osmosis definition, 1 mark contrast.

Q13. [3 marks]

• Answer: Rate plateaus as carrier proteins saturated; all available transporters in use; gradient reduced.
• Teaching note: Fig shows plateau at 10 min.
• Mark breakdown: 1 mark saturation, 1 mark carriers full, 1 mark gradient/equilibrium.

Q14. [4 marks]

• Answer: Primary – peptide bonds; Secondary – H bonds (α-helix/β-sheet); Tertiary – H/ionic/disulfide/hydrophobic; Quaternary – same as tertiary between subunits.
• Teaching note: Levels build complexity.
• Mark breakdown: 1 mark per level + bond.

Q15. [3 marks]

• Answer: High temp breaks H/ionic/disulfide bonds → denaturation; active site lost; enzyme inactive.
• Teaching note: Beyond optimum temp, structure unfolds.
• Mark breakdown: 1 mark bond break, 1 mark denature, 1 mark active site loss.

Section D: Enzymes and Stem Cells

Q16. [3 marks]

• Answer: Substrate binds active site; enzyme changes shape (induced fit) to strain substrate; lowers activation energy; product released.
• Teaching note: Not rigid lock-key.
• Mark breakdown: 1 mark bind, 1 mark shape change, 1 mark lower Ea.

Q17. [3 marks]

• Answer: Quaternary: 4 subunits (2α,2β) each with haem. Structure allows cooperative O₂ binding/release in blood.
• Teaching note: Cooperativity aids transport.
• Mark breakdown: 1 mark 4 subunits, 1 mark haem, 1 mark O₂ transport.

Q18. [3 marks]

• Answer: Rate increases then plateaus; more substrate → more ES complexes until enzymes saturated.
• Teaching note: Fixed enzyme = limiting at high [S].
• Mark breakdown: 1 mark increase, 1 mark ES complex, 1 mark saturation.

Q19. [2 marks]

• Answer: Embryonic stem cells are pluripotent: can differentiate into all body cell types (not extra-embryonic).
• Teaching note: Pluri ≠ toti.
• Mark breakdown: 1 mark pluripotent, 1 mark differentiate all.

Q20. [1 mark]

• Answer: Replace worn-out blood cells (e.g., red blood cells) / produce blood cells.
• Mark breakdown: 1 mark correct function.