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Question Video: Stating the Cellular Organelle that is the Site of Aerobic Cellular Respiration Biology

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

02:30

Video Transcript

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

Cells perform cellular respiration in order to extract energy from sugar and transfer this energy to a molecule called ATP. Aerobic cellular respiration is a multistep process. These steps are glycolysis, the link reaction, the Krebs cycle, and oxidative phosphorylation. The question asks us to identify the cellular organelle that is the site of the link reaction and Krebs cycle. To work out the answer, let’s first summarize the stages of respiration and where they occur.

Glycolysis is the first stage of cellular respiration and takes place in the cytoplasm of the cell. During glycolysis, one molecule of glucose, the most common respiratory substrate, is converted through a series of reactions into two molecules of pyruvate.

The next stage of cellular respiration is the link reaction, which takes place in the mitochondria. The pyruvate produced during glycolysis moves into the mitochondria, where it becomes the reactant for the link reaction. As there are two molecules of pyruvate produced during glycolysis, there are two link reactions for each molecule of glucose. The product of the link reaction is acetyl coenzyme A, which then enters the third stage of cellular respiration, the Krebs cycle.

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

We now have enough information to answer our question. We have just seen how both the link reaction and the Krebs cycle take place in the mitochondria. So the correct answer to the question “In eukaryotes, what cellular organelle is the site of the link reaction and Krebs cycle?” is mitochondria.

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