It deals with the structure and function of cellular components, such as proteins, carbohydrates, lipids, nucleic acids, and other biomolecules. Cytochemistry – the biochemistry of cells, especially that of the macromolecules responsible for cell structure and function. Molecular biology – the study of biology at a molecular level, including the various systems of a cell, including the interactions between DNA, RNA and protein biosynthesis and learning how these interactions are regulated.