Which of the following statements is incorrect?

The correct answer is Option (3) → Insulin is a fibrous protein

Proteins are classed by molecular shape. In fibrous proteins the polypeptide chains run parallel and form fibre-like structures; in globular proteins the chains coil around to give a spherical shape.

Option (1) Keratin is a fibrous protein — A correct statement. Keratin, present in hair, wool and silk, is a fibrous protein.

Option (2) Fibrous proteins are generally insoluble in water — A correct statement. Fibrous proteins, whose parallel chains are held together by hydrogen and disulphide bonds, are generally insoluble in water.

Option (3) Insulin is a fibrous protein — The incorrect statement. Insulin is a globular protein, usually soluble in water.

Option (4) Myosin is a fibrous protein — A correct statement. Myosin, present in muscles, is a fibrous protein.

NCERT (2026-27 edition):
(b) Globular proteins – “This structure results when the chains of polypeptides coil around to give a spherical shape. These are usually soluble in water. Insulin and albumins are the common examples of globular proteins.”