Which of the following statements is TRUE regarding Earth's earliest organisms?

Question

Quizplus · Accepted Answer

Early Earth's atmosphere lacked oxygen, so the earliest organisms likely carried out fermentation instead of cellular respiration. However, some of these organisms may have possessed rudimentary proton pumps, which can facilitate the movement of protons across a membrane and generate a proton motive force for ATP synthesis. Therefore, the best choice is E, which states that these organisms likely carried out fermentation and may have had rudimentary proton pumps. Use of oxygen as an electron acceptor only became widespread after the evolution of oxygenic photosynthesis, which did not occur until later in Earth's history. Therefore, choices A, B, and D are incorrect.

Which of the Following Statements Is TRUE Regarding Earth's Earliest