Biochemistry is the study of the structure, composition, and chemical
reactions of substances in living systems. Biochemistry emerged as a
separate discipline when scientists combined biology with organic,
inorganic, or physical chemistry and began to study such topics as how
living things obtain energy from food, the chemical basis of heredity,
and what fundamental changes occur in disease. Biochemistry includes the
sciences of molecular biology; immunochemistry; neurochemistry; and
bioinorganic, bioorganic, and biophysical chemistry.