Haemoglobin contains four polypeptide chains. This makes it an example of a protein with
Correct answer: D. quaternary structure
- A. primary structure only
- B. secondary structure only
- C. tertiary structure only
- D. quaternary structure
Explanation
Quaternary structure exists whenever a functional protein is built from more than one polypeptide chain. Haemoglobin has two alpha and two beta chains, each holding a haem group, and their cooperative interaction is what produces the sigmoid oxygen dissociation curve. A single-chain protein such as myoglobin stops at tertiary structure.
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About Proteins
Proteins are polymers of amino acids joined by peptide bonds, and their function depends on primary, secondary, tertiary and quaternary structure. The topic covers fibrous and globular proteins, enzymes, antibodies, hormones and transport proteins, as well as denaturation by heat or extreme pH.
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