Which of the following is not a fibrous protein?

The correct answer is Option (1) → Albumin

Proteins are classed by molecular shape. In fibrous proteins the polypeptide chains run parallel and form fibre-like structures, generally insoluble in water. In globular proteins the chains coil into a spherical shape, usually soluble in water.

Option (1) Albumin — Not a fibrous protein. Albumin is a globular protein, soluble in water.

Option (2) Collagen — A fibrous protein. It is the fibre-forming protein of connective tissue such as tendons and skin.

Option (3) Myosin — A fibrous protein. It is present in muscles.

Option (4) Keratin — A fibrous protein. It is present in hair, wool and silk.

NCERT (2026-27 edition):
(a) Fibrous proteins – “When the polypeptide chains run parallel and are held together by hydrogen and disulphide bonds, then fibre– like structure is formed. Such proteins are generally insoluble in water.”

(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.”