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Everything You Need To Know About Cellular Respiration

Krebs Cycle

What Is Cellular Respiration?
Transition Reaction
Krebs Cycle
Electron Transport Chain


       The Krebs cycle is also called the citric acid cycle. It was named after the founder Hans Krebs. In the cycle there are nine reactions total.

     At the start of these reactions two molecules of Co2 and one more molecule of ATP form. During the cycle NAD and FAD are reduced with the help of electrons that joins each to H+ and forms NADH and FADH2. At this point an extra NADH was formed during the transition reaction.

     There are four molecules of NADH and one molecule of FADH2 for each molecule of pyruvate that enters the mitochondrion. There are two molecules of pyruvate so there are eight molecules NADH and two molecules of FADH2. Just the Krebs Cycle itself synthesizes six molecules of NADH+, two molecules of FADH2 and two molecules of ATP. So far there has been no use of oxygen. There is oxygen only during oxidative phosphorylation during chimiosmosis. The electrons stored on NADH and FADH2 are used during the electron transport to produce ATP. At the end of the Krebs Cycle, the glucose has been catabolized making four molecules of ATP and twelve electron transporter.

A Summary Of The Cycle -     

     Acetyl coenzyme A binds to the oxaloacetate in order to change or convert it to citrate. Water is released from the citrate and then regained in order to form isocitrate. NAD+ binds to isocitrate, leaves as NADH, and carbon dioxide is lost in order to form aketoglutarate. NAD+ binds to aketoglutarate, leaves as NADH, coenzyme A binds and carbon dioxide is lost in order to form succinyl CoA. CoA leaves in order to form succinate. FAD binds to succinate and leaves as FADH2 in order to form fumarate. Water binds to fumarate and forms malate. NAD binds to malate and leaves as NADH which creates a new oxaloacetate molecule ready to bind to another acetyl coenzyme A to start the cycle over again.

Cellular Respiration