AQA GCSE Biology Biology Paper 2 (Higher), June 2025: Question 4

✅ Acceptable Answers (Choose ONE)

• ADH (antidiuretic hormone)
• FSH (follicle stimulating hormone)
• LH (luteinising hormone)
• TSH (thyroid stimulating hormone)

💡 Key Knowledge

The pituitary gland is located at the base of the brain. Often termed the 'master gland', it secretes several hormones into the blood in response to body conditions, which in turn act on other endocrine glands (like ovaries, testes, and thyroid).

❌ Common Errors

• Insulin or Glucagon: These are produced by the pancreas.
• Adrenaline: Produced by the adrenal glands.
• Oestrogen or Testosterone: Produced by ovaries/testes (the pituitary produces FSH and LH, which stimulate them).

🧠 Exam Technique

The mark scheme explicitly notes: "ignore functions of hormones". Do not waste time writing what the hormone does; a simple abbreviation like ADH or FSH gains the full 1 mark immediately.

✅ Correct Answer (Any ONE)

• It would be digested / broken down into amino acids.
• It would be digested by protease enzymes.
• It would be digested in the stomach / small intestine.
• It would be broken down and therefore not absorbed intact into the bloodstream.

💡 Key Knowledge

The question states: "hGH is a protein". When any protein enters the alimentary canal:

• Hydrochloric acid and proteases (e.g. pepsin in the stomach, trypsin in the small intestine) break peptide bonds.
• The protein loses its specific 3D shape (denatures/breaks down) into individual amino acids, completely destroying its hormonal function.

❌ Common Errors

• Vague answers like "it gets dissolved" or "it wouldn't work" (does not explain the biological mechanism).
• Saying it is digested by amylase or lipase instead of protease.

🧠 Exam Technique

Always spot the clue in the stem: "hGH is a protein". Whenever an exam mentions a drug is a protein, link it directly to digestion by enzymes/proteases or breakdown into amino acids.

✅ Step-by-Step Mark Scheme Breakdown

1. Mark 1: Isolate / cut the hGH gene from human DNA / chromosome.
2. Mark 2: Join / insert the hGH gene into a (cut) bacterial plasmid.
3. Mark 3: Put / insert the plasmid (vector) into a bacterium / bacterial cell.
4. Mark 4 (Enzymes): State that an enzyme is used at a suitable stage (e.g. to cut the human DNA or to join/insert the gene into the plasmid).

💡 Key Knowledge & Terminology

• Vector: A carrier used to transfer genetic material (here, a bacterial plasmid - a small ring of DNA).
• Restriction Enzymes: Used to cut open plasmids and isolate the desired gene.
• DNA Ligase: Enzyme used to join the sticky ends of the human gene and plasmid together.

🧠 Exam Technique: Figure 4 Clues

Figure 4 directly states: "Several steps using enzymes and plasmids". Top students use the labels provided in the diagram as a checklist: did you mention the human gene, the enzymes, the plasmid, and inserting it back into the bacterium?

❌ Common Errors

• Missing out the plasmid stage entirely and claiming scientists "inject the gene straight into the bacterium".
• Forgetting to state the role of enzymes (needed for Mark 4).
• Confusing bacterial cell walls with animal membranes.

✅ Acceptable Reasons (Any TWO)

• Purity / Extraction: hGH is easier to isolate / purify / extract from bacterial culture.
• Yield / Volume: Can be produced in much larger quantities.
• Immune Response: No / lower risk of immune reaction or rejection.
• Infection / Disease: No / lower risk of transmitting pathogens / diseases from animals to humans (e.g. BSE / prion disease).
• Contaminants: Less risk of contamination with animal waste products, drugs, or hormones (e.g. urea, animal antibiotics).
• Effectiveness: Genetically engineered hGH is the exact human protein (correct shape/structure), so it works more effectively in human bodies.

❌ Disallowed Answers (Watch the Constraints!)

• Ethical / Religious reasons: The question forbids this (e.g. "animals aren't harmed" or "religions forbid touching animal urine" get 0 marks).
• Cost: Mark scheme explicitly states: "ignore reference to cost" (e.g. "it is cheaper" gets 0 marks).
• Speed: Mark scheme explicitly states: "ignore reference to speed of production" (e.g. "bacteria grow faster" gets 0 marks).

🧠 Exam Technique

Read negative constraints with extreme care! Questions specifying "Do not refer to..." have rigid exclusion criteria in the mark scheme. Stick strictly to biological advantages: purity, large-scale yield, exact molecular match, and zero risk of cross-species disease transmission.