(i) Proteins are the macromolecules formed by bonding together many amino acids.
(ii) Proteins of animal origin are called as first class proteins.
(iii) We get 4 kcal of energy per gram of proteins.
(iv) Amino acids are obtained after digestion of proteins.
(v) These amino acids are absorbed in the body and transported upto each organ and cell via blood.
(vi) From these amino acids, organs and cells produce various proteins necessary for themselves and the whole body. Eg. Melanin, Keratin, Ossein, hemoglobin, etc.