Biomolecules or biological molecules are the molecules that are present in the living system and needed for their growth, reproduction, and survival. They may be either endogenous (produced inside) or exogenous. Exogenous products are generally natural products (produced by living system). Using the exogenous products, cells produce necessary macro and micro-sized molecules through cell processes called as anabolism and catabolism. Some of the smaller biomolecules (vitamins) produced by the primary metabolism are essential for the living, while the secondary metabolites (hormones) assists the living system in their survival. Macro sized biomolecules are four in number and they are carbohydrates, proteins, lipids and nucleic acid.