suck vs soak up

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

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

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

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

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

suck (verb)	soak up (verb)
give suck to	devote (oneself) fully to
draw into the mouth by creating a practical vacuum in the mouth	take in, also metaphorically
take in, also metaphorically
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.