Identify the source of the electrons that travel down the electron transport chain. explain why oxygen is the final electron acceptor in aerobic cellular respiration.

1) The electrons that travel down the electron transport chain come from the NADH and FADH2 molecules produced in the three previous stages of cellular respiration : glycolysis, pyruvate oxidation, and the citric acid cycle.

2) At the end of the electron transport chain is the Oxygen  that will accept electrons and picks up protons to form water.
If the oxygen molecule is not there the electron transport chain will stop running, and ATP will no longer be produced.

The number of protons in a nucleus