During the electron transport chain, which process leads to the production of large amounts of atp? a. nadh combines with fadh 2 to produce large amounts of atp. b. water is broken down into oxygen and hydrogen ions to produce atp. c. high-energy electrons pump hydrogen ions against the concentration gradient. d. energy carriers release carbon dioxide that flows through the mitochondrial membrane.

C. High energy electrons pump hydrogen ions  against the concentration gradient. The final stage of cellular respiration is oxidative phosphorylation. This is why you breathe oxygen. In the electron transport chain, electrons  are passed from one molecule to another.  At the end of the electron transport chain, oxygen accepts the electrons and picks up protons to form water. The electron transport chain occurs in the mitochondria, which has a  double plasma membrane. The electrons are passed along proteins, or cytochromes, in the inner membrane. Each time an electron is passed, it pumps a hydrogen ion, or proton, into the the intermembrane space, or the space between the two membranes. At the end of the electron transport chain is an ATP synthase. The ATP synthase pumps the hydrogen back in, and the electron attaches to an oxygen along with the hydrogen, making water. The energy is transferred to an ADP, which becomes an ATP when it uses the energy to add a phosphate. 

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