Explain how chaperone proteins assist in the correct folding of newly synthesised polypeptides.

IB DP Biology Higher Level (2023 syllabus) — B1.2 Proteins · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Newly synthesised polypeptides emerging from ribosomes are at risk of misfolding or aggregating. Chaperone proteins bind to exposed hydrophobic regions of the unfolded or partially folded polypeptide, preventing premature or incorrect interactions. The chaperone then uses energy from ATP hydrolysis to change conformation, releasing the polypeptide so it can fold correctly. This cycle of binding and release can repeat until the polypeptide reaches its stable, correctly folded tertiary or quaternary structure.

Examiner tips

  • Use the term ‘exposed hydrophobic regions’ to show understanding of the binding site.
  • Mention ATP hydrolysis explicitly – examiners look for the energy source.
  • Explain that the process is iterative – repeat cycles until correct folding.
  • Keep the answer concise, matching the 4 marks.

Mark scheme (4 marks)

  1. Newly synthesised polypeptides emerging from ribosomes are at risk of misfolding or forming incorrect interactions with other polypeptides / aggregating.
  2. Chaperone proteins bind to exposed hydrophobic regions of the unfolded/partially folded polypeptide, preventing premature or incorrect interactions.
  3. Chaperones use energy from ATP hydrolysis to drive conformational changes that release the polypeptide, allowing it to fold correctly.
  4. The process may be repeated (iterative cycles of binding and release) until the polypeptide achieves its stable, correctly folded tertiary/quaternary structure.

Key terms in this question

chaperone protein

Related

More Proteins questions

▶ Try answering this question with AI marking (free) →