smell up vs scent

smell up is not a noun while scent is a noun.

Word	Noun	Adjective	Verb	Adverb
smell up	No	No	Yes	No
scent	Yes	No	Yes	No

As verbs, scent is a hypernym of smell up; that is, scent is a word with a broader meaning than smell up:

Other hypernyms of smell up include odorize, odourise.

smell up (noun)	scent (noun)
	any property detected by the olfactory system
	an odor left in passing by which a person or animal can be traced
	a distinctive odor that is pleasant

smell up (verb)	scent (verb)
cause to smell bad; fill with a bad smell	apply perfume to
	catch the scent of; get wind of
	cause to smell or be smelly