The correct order of the steps of Cellular Respiration is as follows:
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Glycolysis takes place in the cytoplasm and breaks down glucose to form two molecules of pyruvate. 2 ATP are produced and NADH is saved for later.
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Two molecules of pyruvate move into the mitochondria where they are converted into Acetyl CoA. More NADH is produced and CO2 is released.
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Citric Acid/Kreb's Cycle: the carbons that are left from the initial glucose are oxidized, releasing more CO2. NADH and FADH2 and 2 ATP molecules are produced.
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The electron transport chain: the NADH and FADH2 give up electrons, energy is released and captured as it moves from a high concentration to a low concentration. Energy is used to produce about 32-34 ATP.
So, the final order is: 1, 4, 3, 2.