The quaternary structure of a protein exists only when the molecule
- A. contains a disulphide bridge
- B. is fibrous
- C. consists of two or more polypeptide chains associated together
- D. contains more than one hundred amino acids
Explanation
Quaternary structure describes how separate polypeptide subunits fit together, as in haemoglobin with its two alpha and two beta chains, and a single chain protein such as myoglobin therefore stops at the tertiary level. The subunits are held by the same weak interactions that stabilise tertiary structure. Chain length alone has nothing to do with it.
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