A Level Biology A Paper D June 2021 Notes

Instructions and Information

• Use black ink, HB pencil allowed for graphs and diagrams.
• Write answers in the space provided, use lined pages at the end for extra space.
• Answer all questions; marks awarded for correct methods.
• Total marks: 100.
• Quality of extended response assessed in questions marked with an asterisk (*).
• Required: Insert (inside document), ruler, scientific/graphical calculator.
• Time allowed: 2 hours 15 minutes.*

Section A

• Focus: Multiple choice questions, time suggested: 20 minutes.

Key Questions

1. Liver Function

   • Not a function: C (storage of excess amino acids as protein)

2. Control of Blood Glucose

   • Correct statement: B (Glucagon stimulates conversion of glycogen to glucose)

3. **Protein Export Path

   • Correct path: C (Rough ER → Golgi apparatus → Secretory vesicle)

4. Enzyme Catalyzed Reactions

   • True statement: A (Binding of a substrate to the active site can weaken bonds)

5. End-Product Inhibition

   • Example: B (Isoleucine inhibits E7)

6. Cell Specializations

   • Correct description: B (biconcave shape, no nucleus for erythrocytes)

7. Action Potential Events

   • Correct description: D (Position 4, no Na+ channels open, no K+ channels open)

8. Action Potential Graph Interpretations

   • Correct statement: C (Hyperpolarization at 5, repolarization at 6)

9. Pregnancy Test Interpretation

   • True statement: B (Strip 2, hCG binds to mobile antibodies captured by fixed at Results line)

10. Neuron Structure Identification

    • Correct identification: A (axon, dendron, sensory neuron)

11. Nervous Transmission

    • Incorrect statement: D (Nodes of Ranvier act as insulators)

12. Nervous System Statements

    • Correct: B (1 and 2 are correct)

13. Coenzymes in Cellular Respiration

    • Correct: B (NAD and FAD are coenzymes, NAD is reduced)

14. Respirometer Investigation

    • Incorrect statement: A (Level in left-hand arm decreases)

15. Water Transport in Plants

    • Incorrect: B (Water does not pass through Casparian strip)**

Section B

• Focus: Short answer questions requiring written responses.

Heart and Brain Questions

• Identify structures and describe effects of injuries to brain regions.
• Understand the control of heart rate by the nervous system.

Pancreas and Insulin Secretion

• Identify structures in pancreas micrograph.
• Effect of nifedipine on insulin secretion, calcium channel block explanation.

Liver and Enzymes

• Identify liver structures, describe enzyme adaptations.
• Understanding of coenzymes and inhibition in enzyme activity.

Photosynthesis and Terrariums

• Hill reaction: role of DCPIP and electron transport.
• Adaptations for plant growth in terrariums, reasons why cacti may not thrive.

Transpiration and Xylem

• Potometer usage and effects of air movement on transpiration rates.
• Calculate standard deviation, and factors affecting leaf area estimation.
• Description of xylem cell production.

Tissue Fluid and Ultrafiltration

• Effect of solute concentrations on water potential and oncotic pressure.
• Calculation of net driving force, implications of kidney disease on fluid dynamics.
• Comparison between lymph and tissue fluid composition.

Notes

• Always read questions carefully and base answers on evidence provided.
• Consider practical applications and implications of theoretical knowledge in experiments and real-world scenarios.