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How do organisms use oxygen to release energy from food?
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Biology
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Organisms use oxygen to release energy from food through a process known as cellular respiration. This process allows cells to convert the chemical energy stored in food molecules into adenosine triphosphate (ATP), the primary energy carrier used to fuel life-sustaining activities.123
The process occurs in three main stages:
- Glycolysis: This initial, anaerobic stage breaks down glucose into pyruvate, yielding a small amount of ATP.13
- Tricarboxylic Acid (TCA) Cycle: Also known as the Krebs cycle, this stage processes the products of glycolysis, releasing carbon dioxide as a waste product and transferring high-energy electrons and hydrogen atoms to carrier molecules (NADH and FADH).13
- Oxidative Phosphorylation: This final stage requires oxygen. High-energy electrons are passed along an electron transport chain located in the mitochondria (or plasma membrane in bacteria). Oxygen acts as the final electron acceptor, combining with electrons and protons to form water. This flow of electrons releases significant energy, which drives the synthesis of large amounts of ATP.3145
By using oxygen, aerobic organisms extract far more energy from food than those relying solely on anaerobic processes like fermentation.36