Question

Differentiate between fibrous and globular proteins.

Hint:

Think about chain arrangement (parallel fibre vs coiled sphere), water solubility, and structural vs functional role.

Answer 1

Concept: Proteins are classified by their molecular shape (secondary/tertiary structure) into fibrous and globular types.

Step 1: Fibrous proteins.
The polypeptide chains lie side by side (parallel) and are held together by strong hydrogen bonds and disulphide bonds, giving a long, thread-like, fibre structure. They are insoluble in water, mechanically strong and chemically stable, and perform mainly structural roles. Examples: keratin (hair, nails), myosin (muscle), collagen (tendon), fibroin (silk).

Step 2: Globular proteins.
The polypeptide chains coil and fold around themselves to give a compact, roughly spherical (ball-like) shape. They are usually soluble in water (and dilute acids/bases) and are more sensitive to heat and pH. They carry out functional/dynamic roles such as enzymes, hormones and transport. Examples: insulin, albumin, haemoglobin, many enzymes.

Summary: Fibrous = parallel chains, fibre shape, water-insoluble, structural (keratin, collagen); Globular = coiled chains, spherical shape, water-soluble, functional (insulin, haemoglobin).