Question

Name the structure that confers the arrangement of the protein that contains two or more polypeptides in a three dimensional complex.

• A. Primary structure
• B. Secondary Structure
• C. Tertiary Structure
• D. Quarternary structure

Hint:

Hemoglobin is a classic example of a protein with quaternary structure, consisting of four polypeptide subunits (\(2\alpha\) and \(2\beta\) chains) working cooperatively to transport oxygen.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Proteins exhibit hierarchical levels of structural complexity.
The organization of single or multiple polypeptide chains in space determines the overall 3D structure and biological function.

Step 2: Detailed Explanation:
Let us define the four levels of protein structure:
Primary Structure: The linear sequence of amino acids linked by covalent peptide bonds along the polypeptide chain.
Secondary Structure: Local spatial conformations of the polypeptide backbone, stabilized by hydrogen bonds (e.g., \(\alpha\)-helices and \(\beta\)-pleated sheets).
Tertiary Structure: The overall three-dimensional folding of a single polypeptide chain, stabilized by hydrophobic interactions, hydrogen bonds, ionic bonds, and disulfide bridges among side-chain residues.
Quaternary Structure: The assembly and spatial arrangement of multiple distinct polypeptide chains (referred to as subunits or protomers) that pack together to form a functional multi-protein complex.
Because the question refers to the arrangement of two or more polypeptide chains in a three-dimensional complex, the quaternary structure is the correct level of organization.

Step 3: Final Answer:
The quaternary structure describes the arrangement of two or more polypeptide chains in a three-dimensional complex.