protoheme vs haemitin

protoheme and haemitin both are nouns.

Word	Noun	Adjective	Verb	Adverb
protoheme	Yes	No	No	No
haemitin	Yes	No	No	No

As nouns, protoheme and haemitin are synonyms defined as:

protoheme and haemitin: a complex red organic pigment containing iron and other atoms to which oxygen binds

Other synonyms of protoheme include haem, hematin, heme.

protoheme (noun)	haemitin (noun)
a complex red organic pigment containing iron and other atoms to which oxygen binds	a complex red organic pigment containing iron and other atoms to which oxygen binds