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Cellular Respiration

Krebs Cycle

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Home | Glycolysis | Krebs Cycle | Electron Transport Chain | Transition Reaction

The Krebs cycle also known as the Citric Acid cycle, gets its name from its founder, Hans Krebs. The Krebs cycle is composed of a series of nine reactions. First, an enzyme takes out the acetyl group from aceytl co-a.  This two carbon molecule then combines with a four carbon molecule to form a six carbon molecule called citrate (citric acid). The next reactions of the Krebs Cycle are classified as oxidation/reduction reactions. They start with the formation of two molecules of CO2 and one molecule of ATP. During the cycle electrons reduce FAD and NAD that joins H+ ions to form FADH2 and NADH. Note that an extra NADH was formed during the transition reactions.

Krebs Cycle (Citric Acid Cycle)

Four molecules of NADH and one molecule of FADH2, are produced for each molecule of pyruvate that enters into the mitochondrion. Since two molecules of pyruvate enter the matrix for each molecule of oxidized glucose, right molecules of NADH+ and two molecules if FADH2 are produced. The Krebs Cycle synthesizes six molecules of NADH+, two molecules of FADH2, and two molecules of ATP just by itself.
Oxygen was not used in this stage. Oxygen is only used in oxidative phosphorylation during chimiosmosis. Electrons that were stored on NADH and FADH2 are used during the electron transport to produce ATP. After one cycle of the krebs cycle, the molecule of glucose gets completely cataolized forming 4 molecules of ATP and 12 electron transporters.

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