Explain how collagen's structure is related to its function as a structural protein in connective tissue.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Collagen is made of three polypeptide chains that wind around each other to form a triple helix.
The chains are held together by hydrogen bonds (and covalent cross‑links) which give the helix great tensile strength.
Several triple helices associate to form fibrils and then fibres, producing an insoluble, rope‑like structure.
This fibrous, highly organised structure allows collagen to provide mechanical support and resist tension in connective tissues such as tendons, skin and bone matrix.
The chains are held together by hydrogen bonds (and covalent cross‑links) which give the helix great tensile strength.
Several triple helices associate to form fibrils and then fibres, producing an insoluble, rope‑like structure.
This fibrous, highly organised structure allows collagen to provide mechanical support and resist tension in connective tissues such as tendons, skin and bone matrix.
Examiner tips
- Use the word "triple helix" and mention hydrogen bonds/cross‑links. Show the hierarchy: chains → helix → fibrils → fibres. Link the rope‑like structure to tensile strength and mechanical support.
Common mistakes
- Confusing collagen with other proteins (e.g., keratin). Omitting the role of hydrogen bonds or cross‑links. Failing to connect the fibrous structure to its mechanical function.
Mark scheme (4 marks)
- Collagen consists of three polypeptide chains wound together into a triple helix
- Hydrogen bonds (and/or cross-links) between the chains hold the triple helix together, giving tensile strength
- Collagen triple helices aggregate into fibrils and fibres, creating an insoluble, rope-like structure
- The resulting fibrous structure provides mechanical support / resists tension in connective tissues such as tendons, skin, or bone matrix
Key terms in this question
connective tissue · structural protein
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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