What are physical and chemical changes or reactions that occur within the body collectively known as?

Metabolism is the sum total of all the reactions that take place within each cell of a living organism and that provide energy for vital processes and for synthesizing new organic material. It involves the process that take place to breakdown a complex molecule to generate energy for the body.

Physiology is a branch of biology that deals with the study of how living organisms and their various parts carry out their normal functions.

Assimilation is the process that involves the movement of digested food molecules into the cells of the body where they are used.

Excretion is a process by which waste are eliminated from the body.