Question

Oxidative phosphorylation, as it occurs in modern eukaryotes, is a complex process that

probably arose in simple stages in primitive bacteria. Which mechanism is proposed to
have arisen first as this complex system evolved?
(a) electron transfers coupled to a proton pump
(b) the reaction of oxygen with an ancestor of cytochrome c oxidase
(c) ATP-driven proton pumps
(d) the generation of ATP from the energy of a proton gradient

Answer 1

The earliest proposed mechanism to have evolved in the development of oxidative phosphorylation in ancient bacteria is the coupling of electron transfers to a proton pump, which enabled the generation of a proton gradient across a membrane.

Step-by-step explanation:

The evolution of oxidative phosphorylation is believed to have occurred in several stages in primitive bacteria. Among the proposed mechanisms that might have arisen first, electron transfers coupled to a proton pump is suggested as the initial step. This early form of electron transport would have been advantageous as it could create a proton gradient across a membrane, which is a source of energy that could later be harnessed to synthesize ATP. As oxygen levels in the environment began to rise, reactions involving oxygen, including the reaction of oxygen with an ancestor of cytochrome c oxidase, would have become more prevalent and contributed to the efficiency and effectiveness of the process. Over time, this primitive system became the foundation for the complex machinery of oxidative phosphorylation as we understand it in modern eukaryotes.