Electron Transport System

The oxidation of NADH and FADH₂ create a proton gradient that powers ATP synthase. This is called chemiosmosis and, similar to chemiosmosis in photosynthesis, involves the movement of hydrogen ions down a concentration gradient.

Oxygen acts as the final electron acceptor in the electron transport system. Without oxygen, the NADH and FADH₂ remain in their reduced state, and no NAD⁺ or FAD would be available for the Kreb's cycle. 

Below is a pictorial representation of each step of aerobic cellular respiration. Most of the ATP is created in the electron transport system.

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 Self-Check

Watch the following video and complete the quiz questions.