Final answer:
Activation of a Gs alpha subunit results in the initiation of the adenylyl cyclase/cAMP signaling pathway, which leads to a phosphorylation cascade affecting cellular processes.
Step-by-step explanation:
The outcome of activation of a Gs alpha subunit is the initiation of the adenylyl cyclase/cAMP signaling cascade. When the activated alpha subunit associates with adenylyl cyclase, it catalyzes the conversion of ATP to cAMP. This cAMP then serves as a second messenger in the cell, activating protein kinases like protein kinase A (PKA), which begins a phosphorylation cascade that ultimately alters various cellular processes including gene expression.