AQA A-Level Biology Paper 1, June 2023: Question 1

✅ Correct Answer

Three structural features found in all viruses:

1. Genetic material (accept DNA or RNA / nucleic acid / genome)
2. Capsid (protein coat / capsomeres)
3. Attachment protein (accept glycoprotein)

Function of one named feature (choose one):

• Genetic material: Codes for viral proteins.
• Capsid: Protects the genetic material (RNA/DNA).
• Attachment protein: Binds to receptors on the host cell.

💡 Key Knowledge

Viruses are exceptionally simple biological entities. Unlike cells, they lack cytoplasm, organelles, and a plasma membrane. They consist strictly of a core genetic blueprint protected by a protein coat, often studded with surface markers used to infect target cells.

🧠 Exam Technique

This is a 2-mark question split across naming features and describing a function. Ensure you state all three structures clearly to unlock marking points. Do not confuse generic terms like "genetic information"—stick strictly to "genetic material", "DNA", or "RNA".

❌ Common Errors

Students frequently lose marks by writing vague terms like "membrane" or "cytoplasm" for viral structures, or by forgetting to state the function of a named feature when required.

✅ Correct Answer

Acellular reason (any one):

• No cell-surface membrane
• Not made of cells / no cellular structure
• No cytoplasm or organelles

Non-living reason (any one):

• Have no independent metabolism / metabolic reactions
• Cannot independently move, respire, replicate, or excrete
• Have no nutrition

💡 Key Knowledge

In biology, living organisms must maintain homeostasis, undergo metabolism, and reproduce independently. Because viruses require a host cell's machinery to replicate and carry out metabolic processes, they exist in a grey area between living and non-living, classified strictly as infectious non-living particles.

🧠 Exam Technique

Read the question carefully: it asks for explanations regarding both parts ("acellular" and "non-living"). You must provide one valid point for each aspect to capture both available marks.

❌ Common Errors

Writing generic statements like "they are dead" or "they don't breathe" will not gain credit. Examiners look for precise scientific vocabulary such as "metabolism", "cell-surface membrane", and "independent replication".

✅ Correct Answer

Any one of the following:

• Viruses do not have bacterial structures, enzymes, or cell walls (e.g., murein / peptidoglycan).
• Viruses do not have metabolic processes / biochemical pathways for antibiotics to target.
• Viruses do not have ribosomes (or 70S ribosomes) to inhibit.

💡 Key Knowledge

Antibiotics work by targeting structures or metabolic pathways unique to bacteria, such as the synthesis of peptidoglycan cell walls or 70S bacterial ribosomes. Since viruses rely entirely on host cell machinery (which are eukaryotic and structurally distinct from bacteria) and lack their own metabolic pathways, antibacterial drugs have no molecular targets on a virus.

🧠 Exam Technique

This is a quick 1-mark recall question. Keep your answer direct and focused on the structural or metabolic differences between bacteria and viruses.

❌ Common Errors

A classic misconception is stating that "viruses are too small for antibiotics" or "viruses are immune". The actual scientific reason is a lack of targeted bacterial structures and metabolic processes.