Which of the following statements best explains the observation that proton pumps are used by organisms in every domain of life?
A) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.
B) The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.
C) Cells of each domain evolved proton pumps independently when oceans became more acidic.
D) Proton pumps are necessary to all cell membranes.

Question

Quizplus · Accepted Answer

Proton gradients are fundamental to energy conversion processes in cells, such as ATP synthesis, which is essential for life. The use of proton gradients by cells from the common ancestor of all three domains of life (Bacteria, Archaea, and Eukarya) explains why organisms in every domain have proton pumps. This ancestral trait was passed down through evolutionary history to all current forms of life.

Which of the Following Statements Best Explains the Observation That