In the context of cellular respiration, the term "energy tally" typically refers to the total amount of energy (in the form of ATP - adenosine triphosphate) produced during the process of cellular respiration. Cellular respiration is the biochemical pathway that cells use to convert glucose and other organic molecules into energy, which is then used to power various cellular processes.
Here's an overview of the key stages of cellular respiration and their contribution to the energy tally:
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Glycolysis: This is the initial stage that occurs in the cytoplasm, where one molecule of glucose is broken down into two molecules of pyruvate. Glycolysis produces a net gain of 2 ATP and 2 NADH (which can further contribute to ATP production in later stages).
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Krebs Cycle (Citric Acid Cycle): This occurs in the mitochondria. Each molecule of acetyl-CoA (derived from pyruvate) enters the cycle, producing 3 NADH, 1 FADH2, and 1 ATP (or GTP) per turn. Since each glucose molecule results in two acetyl-CoA molecules, the Krebs cycle effectively produces 6 NADH, 2 FADH2, and 2 ATP for each glucose.
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Electron Transport Chain (ETC): This takes place on the inner mitochondrial membrane. The NADH and FADH2 produced in earlier stages donate electrons to the electron transport chain, leading to the production of a large amount of ATP. The theoretical maximum yield from the complete oxidation of one glucose molecule via the ETC can be around 28 to 34 ATP, depending on the efficiency of the process.
By summing the ATP produced in each of these stages, the total energy tally from one molecule of glucose during cellular respiration is typically around 30 to 38 ATP, although the exact number can vary based on the efficiency of the processes and the type of cells in which respiration occurs.
So, when someone refers to the "energy tally" in cellular respiration, they are essentially summarizing the total ATP yield from the complete breakdown of glucose during this metabolic process.