rise up vs straighten

rise up and straighten both are verbs.

Word	Noun	Adjective	Verb	Adverb
rise up	No	No	Yes	No
straighten	No	No	Yes	No

As verbs, straighten is a hypernym of rise up; that is, straighten is a word with a broader meaning than rise up:

rise up (verb)	straighten (verb)
come to the surface	put (things or places) in order
stand up on the hind legs, of quadrupeds	make straight or straighter
take part in a rebellion; renounce a former allegiance	make straight
	straighten by unrolling
	straighten up or out; make straight
	get up from a sitting or slouching position