Respiration is the process of creating energy within a cell. This process happens on the cell membrane. If you can find a diagram of a mitochondria, you can see that it looks like a maze inside; all these folds are membranes where energy is created.
Glycolysis, Kreb's Cycle and the Electron Transport Chain steps in the process of cellular respiration. Think of them as three stages in the same process. During Glycolysis, glucose and 2 ATP molecules are broken down into 2 3-carbon sugars (glucose is broken in half) and transformed again to create 4 ATP molecules and 2 NADH molecules, which ultimately results in 2 pyruvate molecules. During Kreb's Cycle, or the Citric Acid Cycle, pyruvate is combined with NAD and coenzyme A to create NADH, Carbon dioxide and acetyl CoA. During the Electron Transport Chain, protein channels act as turbines to convert NADH and acetyl CoA into water, carbon dioxide and energy (electrons).
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