Quaternary Structure & Haemoglobin — NEET Biology
✅ Asked in NEET 2024Some proteins are an assembly of more than one polypeptide or subunits. The manner in which these individual folded polypeptides or subunits are arranged with respect to each other (e.g. linear string of spheres, spheres arranged one upon each other in the form of a cube or plate etc.) is the architecture of a protein otherwise called the quaternary structure of a protein. Adult human haemoglobin consists of 4 subunits. Two of these are identical to each other. Hence, two subunits of α type and two subunits of β type together constitute the human haemoglobin (Hb).
Quaternary structure refers to how multiple polypeptide subunits arrange in 3D space—this is what NTA tests. Adult human haemoglobin has 4 subunits: 2 α-type and 2 β-type in a specific arrangement. Students often confuse quaternary structure with tertiary structure (single polypeptide folding) or forget that quaternary structure requires multiple subunits. The key to scoring: remember that quaternary structure = multiple subunits arranged spatially, while tertiary = one polypeptide's 3D shape. For haemoglobin specifically, always recall the 2α-2β composition and that this arrangement is crucial for its oxygen-binding function.
This paragraph was tested 2 times in NEET.
Match List-I with List-II:List-I A. Primary structure of protein B. Secondary structure of protein C. Tertiary structure of protein D. Quaternary structure of protein List-II I. Human haemoglobin II. Disulphide bonds III. Polypeptide chain IV. Alpha helix and β sheet Choose the correct answer:
Given below are two statements:Statement I: A protein is imagined as a line, the left end represented by first amino acid (C-terminal) and the right end represented by last amino acid (N-terminal). Statement II: Adult human haemoglobin consists of 4 subunits (two subunits of α type and two subunits of β type). Which of the following is correct?
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
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