Metabolism refers to the sum of all chemical reactions which occur in the human body and indeed all organisms. These chemical reactions are necessary for the sustainability of life and permit organisms to multiply as well as maintain and grow themselves while responding to the environment. Typically, scientists classify metabolic activity into two categories: Catabolism and Anabolism. The former refers to the breaking down of larger molecules into simpler constituent units while the latter refers to the synthesis of larger molecules such as protein as well as others.

Chemical reactions in our body occur through metabolic pathways that transform a molecule under different stages with the help of enzymes. These enzymes play a hugely important role in organisms so that desirable reactions can occur without the necessary activation energy or other pre-requisitions that may be required. The same time these biological catalysts also act as regulators of the metabolic pathways and play a role in homeostasis in the body.

The metabolic activity usually ends up determining what kind of substances an organism may find nutritious and what it may find toxic. For instance, simple organisms like bacteria can utilize the chemical hydrogen sulfide as a nutrient whereas most eukaryotes would find it deadly.

Term papers along with research papers that deal with metabolic activity and metabolism in general are typically more challenging than those in other courses. Enzymes, metabolic pathways and types of reactions usually dominate in the starting courses while more advances courses may require detailed primary research. This is especially true for Masters and Ph. D. level students.