I have never heard of straigthforward definitions of these fields in my college lectures, and the Internet searches were not very helpful. However, from what I have learned at different subjects, this what I understand of the following areas.
- Biochemistry: The study of metabolic pathways, enzyme kinetics, bioenergetics and the chemical mechanisms of the reactions. It does study molecular structure, but only of small molecules such as monomers, metabolites and coenzymes.
- Molecular biology: The study of information pathways, such as transcription, splicing and replication. It applies as well to techniques such as PCR.
- Molecular genetics: The study of how a genotype creates a particular phenotype. For example, it would be the study of why an allele produces smooth peas while another one produces wrinkled ones.
- Structural biology: Elucidating the structure of macromolecules (proteins, nucleic acids) and their complexes. It uses X-ray crystallography, NMR and cryo-electron microscopy to study them.
So, are my definitions accurate? If not, why?