What field of study focuses on the molecules found in cells?

The field of study that focuses on the molecules found in cells is molecular biology. This discipline examines the molecular mechanisms of various cellular processes, particularly the interactions between different types of cellular molecules, such as DNA, RNA, and proteins. It emphasizes understanding how these molecules come together to maintain cell functions, replicate, and express genes, often employing techniques such as DNA sequencing and recombinant DNA technology.

While genetics also deals with DNA and heredity, its primary focus is on inheritance patterns rather than the specific molecular mechanisms of cellular function. Cell biology looks at the overall structure and function of cells, encompassing various cellular components and processes but not specifically emphasizing the molecular interactions. Biochemistry examines the chemical processes within and related to living organisms, including metabolic pathways, but it doesn't solely focus on the molecular aspects in a biological context like molecular biology does. Therefore, the correct answer is indeed molecular biology, as it encapsulates the study of the molecules that form the basis of cellular activities and interactions.