Myoglobin is an oxygen-storage protein in cardiac and skeletal muscle. Which statement about its structure is correct?
- A It consists of a single polypeptide chain with one heme group and no quaternary structure ✓
- B It has a quaternary structure with cooperative oxygen binding
- C It is a tetramer of four globin chains, each with a heme group
- D It contains two alpha and two beta chains with four heme groups
Correct answer: A. It consists of a single polypeptide chain with one heme group and no quaternary structure
Explanation
Myoglobin is a monomeric protein consisting of a single polypeptide chain (153 amino acids) with one heme group. It lacks quaternary structure and shows non-cooperative (hyperbolic) oxygen binding. Hemoglobin is the tetramer (α2β2) with four heme groups and cooperative binding. This structural difference explains their different oxygen dissociation curves.
Reference: Lehninger Principles of Biochemistry, 7th ed.
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