Question

The given structure of protein corresponds to:

• A. Primary
• B. Secondary
• C. Quaternary
• D. Tertiary

Answer 1

Answer: (D)

Structure of protein has upto 4 levels :
$1.$ Primary structure - Linear sequence of amino acids with 2 terminals :
A. N- terminal : On left side and is represented by the first amino acid (also known as N- terminal amino acid).
B. C- terminal : On right side and is represented by the last amino acid (also known as C- terminal amino acid).
- This structure appears like a thread and is non-functional.
$2.$ Secondary structure - The above mentioned thread is folded in staircase like helix at some portions and in some other forms in remaining portions. This is also non-functional structure.
$3.$ Tertiary structure - Long chain is also folded upon itself to form a hollow woolen ball like structure. To be functional to perform biological activity, proteins should acquire at least tertiary structure.
$4.$ Quaternary structure - Few proteins are made up of 2 or more polypeptides because of which one more arrangement is there between them with respect to each other. This is termed as quaternary structure.
Example: Adult haemoglobin is made up of 4 globulin chains - 2α chains and 2β chains.