Proteins are complex organic nitrogenous substances found in animal and plant tissues. The term protein is derived from Greek : Proteios means primary or holding first place.
Protein is the essential constituent of living cells. Protein make upto 12% of the protoplasm. They are not only responsible for comprising the structure of the cell but are concerned with every function of the cell including those of respiration, catalysis of reactions by enzymes, transport of materials, regulation of metabolism, and defense actions. The foods rich in proteins are known as body building foods.
Proteins are obtained from animal and plant sources. The animal sources of proteins include milk, egg, meat, fish, liver etc. Plant sources of proteins are pulses, nuts and cereals.