protein molecule vs molecule

protein molecule and molecule both are nouns.

Word	Noun	Adjective	Verb	Adverb
protein molecule	Yes	No	No	No
molecule	Yes	No	No	No

As nouns, molecule is a hypernym of protein molecule; that is, molecule is a word with a broader meaning than protein molecule:

protein molecule: any large molecule containing chains of amino acids linked by peptide bonds
molecule: (physics and chemistry) the simplest structural unit of an element or compound

protein molecule (noun)	molecule (noun)
any large molecule containing chains of amino acids linked by peptide bonds	(physics and chemistry) the simplest structural unit of an element or compound
	(nontechnical usage) a tiny piece of anything