What is cAMP and what does it do? How and where is it formed and used?
It is a nucleotide (like those that make up DNA) where the 3' and 5' end of pentose sugar form bond with only one phosphate thereby forming cyclic component.
One of the most important function is as (intracellular) signalling molecule for various pathways including regulation of glycogen and in transcription of enzymes like CYP51 (which is involved in sterol production). It is its importance as signalling molecule that toxins like pertussis toxin manipulate. Pertussis toxin contains units with adenylate cyclase enzymatic ability that can disrupt the concentration of cAMP in cytosol.