<prompt> Which does not act as 2nd messenger?cAMPGuanyl cyclaseDiacyl glycerolInositol triphosphate  <response>: Ans. B. Guanyl cyclase2nd messengers are responsible for conducting and amplifying signals of GPCRs. Following substance act as 2nd messengers:a. cAMP or cGMP causes protein phosphorylationb. IP3- calcium release from ERc. DAG - activates enzymes such as protein kinase C 