Final answer:
The energy released as electrons move through the electron transport chain is used to pump protons across the mitochondrial membrane, creating a proton gradient utilized in the synthesis of ATP.
Step-by-step explanation:
In the electron transport chain, as electrons move along a series of carriers, they release energy that is used to pump protons across a membrane. These protons are pumped from the mitochondrial matrix to the intermembrane space, creating a proton gradient across the inner membrane. This gradient establishes an electrochemical potential which is exploited by ATP synthase to convert ADP and inorganic phosphate into ATP during a process called oxidative phosphorylation.
The electron released from NADH and FADH2 are passed along the chain by carriers which alternate between reduced and oxidized states. This series of reductions and oxidations facilitates the energy release needed to pump the H+ ions. As more protons accumulate in the intermembrane space, the proton-motive force increases, and this stored energy is later used by ATP synthase as protons flow back into the matrix through this enzyme, generating ATP from ADP.