How many ATP molecules does "Chemiosmotic ATP Synthesis" produce?

Asked on by zorico91

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txmedteach | High School Teacher | (Level 3) Associate Educator

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Let's start by considering that chemiosmosis is simply the movement of protons down a combined concentration and electric potential gradient. In other words, when you are considering "chemiosmotic ATP synthesis," you are determining either the number of ATP produced per molecule of a substance or the proportion of ATP that is produced in an overall chemical process.

Here, because it is the most traditional method of analysis, we will consider the number of ATP generated from one molecule of glucose. When glucose is oxidized in mitochondria, it produces 2 `NADH` during glycolysis, a total of 2 `NADH` when converting pyruvate to acetyl-CoA, and a total of 6 `NADH` and 2 `FADH_2` in the Kreb's Cycle. Because of how the intramembranous proteins of the electron transport chain are set up to handle the flow of protons and electrons, each `NADH` produces 2.5 ATP, and each `FADH_2` produces 1.5 ATP. Considering our totals above, this gives us 28 ATP from chemiosmosis. Seeing that the oxidation of glucose yields 36 ATP, you can see clearly that this process must not stop! To halt this process by refusing to breathe, for example, removes the major part of your cells' energy production!

As a side note, some websites use 3 ATP generated per `NADH` or 2 ATP per `FADH_2`. Those numbers do produce a slightly different result; however, in the grand scheme of things, the difference is somewhat small. Also, the true yield of ATP is actually smaller than either number you can calculate because the efficiency of the process certainly isn't 100%!


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