The correct option is D All of the above.
Proteins are the most dynamic biomolecules performing a variety of structural and functional roles. The proteins have a high turn over and constantly old or worn out molecules are broken down and newer molecules are synthesized. Sprinson and Rittenberg (1949) estimated that in man, the average half life of the proteins of whole body is of the order of 80 days. Total body protein synthesis is 400 gram per day, establishing an equilibrium between bodily proteins and circulating plasma proteins.