how many belts should i have under hood? and....

[jasonroman]

was wondering how many belts i should have under hood?
85 gmc sierra 1500. with ac.
think i saw 5.
not sure if its the one further back or the one in front of that one that seems a bit loose. obviously i dont know what that belt is. but today when i replaced the alternator belt that i was missing, i noticed one of them have a bit of play/bounce to it while engine is running.

have on running from fan to a smog pump?
alternater behind that one.
not sure what the next 3 are.

also wondering, on the opposite side of the alternator, there is a compressor. believe its for the air conditioning....wonderin why when i have the heat on...
there is a noise that comes and goes. ive heard this for a while now. and the other day when truck was running and in noticed i was missing alt belt.
i saw the compressor spin= the noise i hear.
why would ac compressor make noise when heat is on?