Question Video: Recalling How Many ATP Molecules Are Produced per Turn of the Krebs Cycle Biology

For each turn of the Krebs cycle, how many molecules of ATP are produced?


Video Transcript

For each turn of the Krebs cycle, how many molecules of ATP are produced?

This question asks us about the Krebs cycle, which is one of the stages in cellular respiration. Cells perform cellular respiration in order to extract energy from sugar and transfer this energy to a molecule called ATP. There are four stages in cellular respiration. These stages are glycolysis, the link reaction, the Krebs cycle, and oxidative phosphorylation.

The question is asking us about the third stage in respiration: the Krebs cycle. So let’s have a closer look at the Krebs cycle. The Krebs cycle takes place in the mitochondria. The product of the link reaction, a two-carbon compound called acetyl coenzyme A, enters the Krebs cycle. This two-carbon compound joins with the four-carbon compound oxaloacetic acid to produce citric acid, which has six carbons. Citric acid then undergoes a series of reactions, eventually reforming oxaloacetic acid.

So what is the point of the Krebs cycle if the intermediate compounds continually cycle? Well, the series of reactions in the cycle both produce ATP and reduce the coenzymes NAD and FAD. Reduced NAD and FAD are crucial for the next, and final, stage of aerobic cellular respiration, which is oxidative phosphorylation. This is the stage in respiration where the majority of ATP is produced, the ultimate aim of the entire process.

Now that we have reviewed the Krebs cycle, let’s take another look at our question. We are asked for each turn of the Krebs cycle, how many molecules of ATP are produced. We can see from the diagram that one molecule of ATP is produced per turn. So the correct answer is one.

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