What study focuses on chemical reactions within a living organism?

The study that focuses on chemical reactions within a living organism is biochemistry. This branch of science explores the chemical processes and substances that occur in biological systems, including the structure and function of biomolecules such as proteins, nucleic acids, carbohydrates, and lipids. By understanding these reactions, researchers can gain insights into how cells function, how diseases develop, and how to create new medical therapies.

In contrast, organic chemistry primarily deals with the structure, properties, and reactions of organic compounds, which typically contain carbon. While organic chemistry plays a role in biochemistry—since many biological molecules are organic—it does not specifically focus on the biochemical processes within living organisms.

Chemistry, in its broader sense, encompasses the study of matter, its properties, and the changes it undergoes but does not specifically target the biochemical reactions that occur in living beings. Inorganic chemistry, on the other hand, focuses on inorganic compounds, which include metals, minerals, and organometallic compounds, rather than the chemical processes within living organisms.

Thus, the focus on chemical reactions within living organisms is distinctly the realm of biochemistry, making it the correct choice.