scent vs smell up

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

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

As verbs, smell up is a hyponym of scent; that is, smell up is a word with a more specific, narrower meaning than scent:

Other hyponyms of scent include stink out, stink up, aromatise, aromatize, perfume, cense, incense, thurify.

scent (noun)	smell up (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

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