suck vs suck up

suck is a noun but suck up is not a noun.

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

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

Other synonyms of suck include absorb, draw, imbibe, soak up, sop up, take in, take up.

suck (noun)	suck up (noun)
the act of sucking

suck (verb)	suck up (verb)
give suck to	try to gain favor by cringing or flattering
draw into the mouth by creating a practical vacuum in the mouth	take in, also metaphorically
take in, also metaphorically	ingratiate oneself to; often with insincere behavior
draw something in by or as if by a vacuum
provide sexual gratification through oral stimulation
be inadequate or objectionable
attract by using an inexorable force, inducement, etc.