AIIMS 2018 Botany Proteins MCQ Question

Hemoglobin (Hb) is a tetrameric protein composed of four polypeptide chains: two alpha (α) and two beta (β) chains, which together facilitate the transport of oxygen (O₂) in the bloodstream. Option A is correct because it accurately reflects this structure. Option B is incorrect as it suggests there are only four α chains, while option C incorrectly states there are four β chains, neither of which can effectively bind oxygen. Option D misrepresents the composition by indicating one α and three β chains, which does not occur in natural hemoglobin.