The fundamental differences in crystal structures and chemical bonding between proteins, organic compounds, and inorganic materials represent foundational chemical and crystallographic knowledge that requires no citation.
The claim states that crystal structures differ fundamentally among proteins, organic compounds, and inorganic materials. This is a baseline, self-evident truth about the chemistry and structural organization of matter (macromolecular folding and peptide backbones versus small-molecule organic crystal packing versus ionic, metallic, or covalent inorganic lattices). Per the instructions, statements that are trivially true by definition or direct everyday/foundational scientific observation are categorized as common knowledge and require no citation.