Question

Which of the following is the biologically active form(s) of a protein?

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

Answer 1

The correct option is C Tertiary structure

The primary structure of a protein is the linear chain of amino acids joined together by peptide bonds. It represents the position of amino acids. There is a free -NH2 group with 𝛂- carbon at the N- terminal of the amino acid and a free -COOH group with 𝛂- carbon at the the C- terminal.
The secondary structure is the folding of the polypeptide chain due to interactions among amino acids. It can be of 2 types. 𝛂- helix resembles a spring. 𝝱- pleated sheet represents segments of polypeptide chain lining up next to each other resembling a pleated paper.
Tertiary structure is the 3D structure formed due to the protein folding upon itself. It is the biologically active form of a protein.
Quaternary structure is the association of 2 or more polypeptide chains. Each chain is considered a subunit. It is the arrangement of each folded polypeptide chain with respect to each other. Eg:- Haemoglobin has 2𝛂 and 2𝝱 chains.