act vs act upon

act is a noun but act upon is not a noun.

Word	Noun	Adjective	Verb	Adverb
act	Yes	No	Yes	No
act upon	No	No	Yes	No

act (noun)	act upon (noun)
something that people do or cause to happen
a subdivision of a play or opera or ballet
a legal document codifying the result of deliberations of a committee or society or legislative body
a short performance that is part of a longer program
a manifestation of insincerity

act (verb)	act upon (verb)
behave in a certain manner; show a certain behavior; conduct or comport oneself	have and exert influence or effect
pretend to have certain qualities or state of mind
discharge one's duties
play a role or part
perform on a stage or theater
behave unnaturally or affectedly
perform an action, or work out or perform (an action)
have an effect or outcome; often the one desired or expected
be suitable for theatrical performance