What is the study of how chemical reactions sustain the normal functioning of living organisms called?

The study of how chemical reactions sustain the normal functioning of living organisms is referred to as biochemistry. This field specifically focuses on the molecular mechanisms of biological processes, including the interactions between different biological molecules and the chemical reactions they undergo. Biochemistry encompasses various topics such as enzyme function, metabolic pathways, and the chemical composition of cells, allowing us to understand how life operates at a molecular level.

While chemistry encompasses the general principles of the study of matter and its interactions, and organic chemistry specifically deals with carbon-containing compounds, these fields do not focus exclusively on the context of living organisms. Molecular biology, on the other hand, studies the interactions between the various systems of a cell, particularly the interactions between DNA, RNA, and proteins. However, it does not emphasize the chemical processes and reactions to the extent that biochemistry does. Thus, biochemistry is the most appropriate label for the study in question.