(A) Heterotrimeric G-proteins are composed of three distinct subunits (α, β, and γ). Receptor activation causes the binding of the G-protein and the α subunit to exchange GDP for GTP, leading (more...) The second class of GTP-binding proteins are monomeric G-proteins (also called small G-proteins).
The ocean acidification is generally caused by the vast amounts of carbon dioxide that humans release in the air gettting absorbed into the ground, causing the PH of the water to rise. Hopefully this helps!