Differentiate between globular and fibrous proteins.

Answer

The main difference in globular and fibrous proteins are given in the following table.
Globular proteins
1. Globular proteins have almost spheriodal shape due to folding of the polypeptide chain
2. Glubular proteins are soluble in water
3. Glubular proteins are sensitive to small changes of temperature and `pH`.
4. Globular poteins possess biological activity.
Fibrous Proteins
1. Polypeptide chains of fibrous proteins consist of thread like molecules which tend to lie side by side to form fibres.
2. Fibrous proteins are insoluble in water.
3. Fibrous proteins are stable to moderate. changes of temperature and `pH`. Therefore, they undergo denaturation on heating or on treatment with acids and bases.
4. Fibrous proteins do not have any biological activity but serve as chief structural material of animal tissues.
For example, keratin in skin, hair, nails, and wool, coolagen in tendons, fibroin in silk and myosin in muscles. That is why they act as enzymes, (maltase, invertase etc), hormones (insulin) antibodies (`gamma` globulins), transport agents (gaemoglobin), etc.

Explanation

Cellulose is found maximum (out of four given) in nature because it is present in plants.