Molecular Biology Molecular biology is usually described as that domain of biology that seeks explanations in terms of the structure and function of molecules of the cell and sometimes of the whole organism. These molecules are most frequently macromolecules such as proteins, nucleic acids and carbohydrates or molecular assemblies such as lipidcontaining membranes and virusesMolecular Biology Molecular biology is usually described as that domain of biology that seeks explanations in terms of the structure and function of molecules of the cell and sometimes of the whole organism. These molecules are most frequently macromolecules such as proteins, nucleic acids and carbohydrates, or molecular assemblies such as lipidcontaining membranes, and viruses