Foundations of Biology of Exam 1 Practice Test

The function of the electron transport chain is to convert the energy stored in electrons carried by NADH and FADH2 into a proton gradient across the inner mitochondrial membrane. As electrons pass through a series of membrane-bound carriers, enough energy is released to pump protons from the mitochondrial matrix into the intermembrane space. This creates a proton motive force (a gradient of both protons and electric potential) across the membrane. ATP synthase then uses the flow of protons back into the matrix through this enzyme to drive the synthesis of ATP from ADP and inorganic phosphate. The chain also ultimately reduces oxygen to water, completing the electron transfer process. This differs from making glucose or acetyl-CoA, and it does not pump protons directly into the matrix without generating a gradient—the gradient across the membrane is essential for ATP production.