Which of the following is insoluble in water?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Keratin
Keratin is a fibrous protein, and fibrous proteins are generally insoluble in water.
Why the other options are incorrect
Option (2) Insulin — Incorrect. Insulin is a globular protein; its chains coil into a spherical shape, and globular proteins are usually soluble in water.
Option (3) Albumin — Incorrect. Albumins are also globular proteins, usually soluble in water.
Option (4) Glucose — Incorrect. Glucose has several –OH groups and is soluble in water.
NCERT (2026-27 edition):
10.2.3 Structure of Proteins – “(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. Some common examples are keratin (present in hair, wool, silk) and myosin (present in muscles), etc.”