in the krebs cycle the acetyl coas that we made during the link reaction will get further broken down remember these acetyl-coa molecules are the remains of our original glucose molecule that we started with at the beginning of respiration by the time we're done with the krebs cycle our glucose will be completely oxidized and broken down to carbon dioxide let's check out how the krebs cycle completes this breakdown [Music] first acetyl coa reacts with a four carbon molecule called oxaloacetate this makes a six carbon molecule called citric acid for this reason the krebs cycle is sometimes called the citric acid cycle [Music] citric acid gets oxidized transferring electrons and hydrogens to nad plus forming nadh this oxidation reaction causes the release of co2 as well now we have a five carbon molecule this molecule undergoes a similar process of oxidation producing another nadh and another co2 now we have a four carbon molecule this four carbon molecule undergoes another chemical reaction that transforms it into a different four carbon molecule the energy released by this reaction is used to join adp and phosphate to form atp [Music] our new four carbon molecule gets oxidized even further transferring electrons and hydrogens to a different electron carrier called fad forming fadh2 fadh2 will serve the same purpose as nadh carrying electrons to the electron transport chain the new four carbon molecule that results gets oxidized one more time forming even more nadh this final reaction also results in making our starting molecule oxaloacetate once again this is why the krebs cycle is a cycle we end up right where we started but notice that we made a bunch of useful molecules along the way perhaps most importantly we have produced many electron carriers nadh and fadh2 that will carry electrons to the electron transport chain we also made atp that can be used as energy as well as carbon dioxide that will be breathed out when you exhale [Music] since we have one more acetyl-coa that needs to go through the krebs cycle let's watch the process one more time with a slightly different perspective that shows its cyclical nature [Music] so if you are doing the respiration interactive activity at bioman biology you should now return to it and complete the tasks related to the krebs cycle the length of the respiration interactive activity is in the description in case you need it if you enjoyed this video please like it subscribe and check out the other free games quizzes and interactive learning experiences at bioman biology