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In eukaryotes, what cellular organelle is the site of the link reaction and Krebs cycle?

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Cells perform cellular respiration in order to extract energy from sugar and transfer this energy to a molecule called ATP.

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Aerobic cellular respiration is a multistep process.

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These steps are glycolysis, the link reaction, the Krebs cycle, and oxidative phosphorylation.

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The question asks us to identify the cellular organelle that is the site of the link reaction and Krebs cycle.

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To work out the answer, let’s first summarize the stages of respiration and where they occur.

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Glycolysis is the first stage of cellular respiration and takes place in the cytoplasm of the cell.

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During glycolysis, one molecule of glucose, the most common respiratory substrate, is converted through a series of reactions into two molecules of pyruvate.

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The next stage of cellular respiration is the link reaction, which takes place in the mitochondria.

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The pyruvate produced during glycolysis moves into the mitochondria, where it becomes the reactant for the link reaction.

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As there are two molecules of pyruvate produced during glycolysis, there are two link reactions for each molecule of glucose.

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The product of the link reaction is acetyl coenzyme A, which then enters the third stage of cellular respiration, the Krebs cycle.

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Like the link reaction, the Krebs cycle takes place in the mitochondria.

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As mentioned, the acetyl coenzyme A produced in the link reaction enters the Krebs cycle, where it joins with a four-carbon compound called oxaloacetic acid to form the six-carbon compound citric acid.

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A series of reactions take place during the Krebs cycle, producing a range of products, including reduced NAD and FAD, which are particularly important for the final stage of respiration, oxidative phosphorylation.

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We now have enough information to answer our question.

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We have just seen how both the link reaction and the Krebs cycle take place in the mitochondria.

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So the correct answer to the question “In eukaryotes, what cellular organelle is the site of the link reaction and Krebs cycle?” is mitochondria.