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Physiology

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Endocrinology

Question
6 out of 10
 

Human insulin differ from beef insulin by: (DNB June-2008)



A 1 Amino acid
B 3 Amino acid

C 4 Amino acid
D 6 Amino acid

Ans. B 3 Amino acid
  1. Insulin is a polypeptide containing two chains of amino acids linked by 2 disulphide bridges between A7 to B7 and A20 to B19.
  2. A third disulphide bridge connects A6 and All .A chain has 21 amino acids and B chain has 30 amino acids.
  3. Half life of insulin in circulation is 5 minutes There is a close similarity between human, porcine and bovine insulins.
  4. The porcine insulin differs only by a single amino acid from human insulin as it has Alanine in place of Threonine at B 30 position.
  5. The BOVINE INSULIN DIFFERS FROM HUMAN INSULIN ONLY BY 3 AMINO ACIDS.

Difference from human amino acid sequence

A chain

B chain

Amino acid position

8 9 10

30

Human insulin

Threonine, Serine Isoleucine

Threonine

Pig and dog insulin

Threonine Serine Isoleucine

Alanine

Cattle and goat insulin

Alanine Serine Valine

Alanine