perk vs perk up

perk is a noun but perk up is not a noun.

Word	Noun	Adjective	Verb	Adverb
perk	Yes	No	Yes	No
perk up	No	No	Yes	No

As verbs, perk and perk up are synonyms defined as:

Other synonyms of perk include gain vigor, percolate, pick up.

perk (noun)	perk up (noun)
an incidental benefit awarded for certain types of employment (especially if it is regarded as a right)

perk (verb)	perk up (verb)
gain or regain energy	gain or regain energy
	cause to be alert and energetic