The major reason that glycolysis is not as energy productive as respiration is that?
- $NAD^+$ is regenerated by alcohol or lactate production, without the high-energy electrons passing through the electron transport chain
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It is the pathway common to fermentation and respiration
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It does not take place in a specialized membrane-bound organelle
- Pyruvate is more reduced than $CO _2$; it still contains much of the energy from glucose
Glycolysis, part of cellular respiration, is a series of reactions that constitute the first phase of most carbohydrate catabolism. Catabolism means the breaking down of larger molecules into smaller ones. The word glycolysis is derived from two Greek words and means the breakdown of something sweet. Glycolysis breaks down glucose and forms pyruvate with the production of two molecules of ATP. The pyruvate end product of glycolysis can be used in either anaerobic respiration if no oxygen is available or in aerobic respiration via the TCA cycle which yields much more usable energy for the cell. When oxygen is present, NADH can pass its electrons into the electron transport chain, regenerating NAD$^+$ for use in glycolysis. When oxygen is absent, cells may use other, simpler pathways to regenerate NAD$^+$ these pathways, NADH donates its electrons to an acceptor molecule in a reaction that doesn’t make ATP but does regenerate NAD$^+$ so glycolysis can continue. This process is called fermentation.