Biochemistry is the study of chemical processes and substances that occur within living organisms. It combines principles from biology, chemistry, and physics to understand the chemical basis of life. Biochemists study the structure and function of biomolecules such as proteins, carbohydrates, lipids, and nucleic acids, as well as the metabolic pathways that allow cells to function. They also investigate the interactions between molecules and how they are regulated, and how these processes are affected by environmental factors and disease. Biochemistry has applications in medicine, agriculture, biotechnology, and many other fields.