The number of amino acids present in insulin are?

Appeared in: ISRO 2024

Explanation

Human insulin is a polypeptide hormone composed of a total of 51 amino acids.
It consists of two chains: the A-chain with 21 amino acids and the B-chain with 30 amino acids.
The A and B chains are connected by two disulfide bridges, which are crucial for its biological activity.
This specific structure was first determined by Frederick Sanger, for which he was awarded the Nobel Prize.

Option A: The number 46 does not correspond to the total amino acid count of insulin or any of its individual chains.
Option B: The number 48 is an incorrect count for the amino acids in an insulin molecule.
Option C: The number 50 is close but incorrect. The precise count is 51 amino acids.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Structure and Composition of Insulin as background academic context rather than a clinical decision trigger.
Understanding the structure of insulin is fundamental to comprehending its function in glucose regulation and the pathophysiology of diabetes mellitus.
The synthesis of insulin from pro-insulin results in the co-secretion of C-peptide. Measuring C-peptide levels is a key diagnostic tool for nurses and doctors to differentiate between type 1 and type 2 diabetes and to assess pancreatic beta-cell function.
What if? If a patient with type 1 diabetes has a measurable C-peptide level, it might indicate a 'honeymoon phase' where some endogenous insulin production is still occurring, which can affect their insulin dosage requirements.

How to Approach the Question

This is a factual recall question from biochemistry/physiology.
Identify the core subject of the question: the composition of the hormone insulin.
Recall the specific details about insulin's structure.
The key fact is that insulin is composed of two chains, an A-chain and a B-chain.
Remember the number of amino acids in each chain (A=21, B=30) and sum them to get the total (21 + 30 = 51).
Select the option that matches this total.

Concept Tested & Keywords

Qb1wYHFMJFZYqeiXCtRNgr

E6 Physiology Essentials Sembulingam 10e Part 2 p. 62-64

E6 Pharmacology KD Tripathi Essentials 9e Part 1 p. 311-313

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) p. 102-104

Practise the full ISRO 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.