iodopsin vs photopigment

iodopsin and photopigment both are nouns.

Word	Noun	Adjective	Verb	Adverb
iodopsin	Yes	No	No	No
photopigment	Yes	No	No	No

As nouns, photopigment is a hypernym of iodopsin; that is, photopigment is a word with a broader meaning than iodopsin:

iodopsin: a violet photopigment in the retinal cones of the eyes of most vertebrates; plays a role in daylight vision
photopigment: a special pigment found in the rods and cones of the retina

iodopsin (noun)	photopigment (noun)
a violet photopigment in the retinal cones of the eyes of most vertebrates; plays a role in daylight vision	a special pigment found in the rods and cones of the retina