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How to Calculate the Krebs Cycle

Organisms get their energy from an organelle in their cells known as the mitochondrion, often dubbed the cell's powerhouse. The production of energy within the mitochondria involves a series of chemical processes. One of the main processes is the Krebs cycle. In the Krebs cycle, acetyl, a fat derivative, is converted into ATP (the energy molecule) and other products that release energy. The Krebs cycle is the second of three processes that convert simple sugar into energy and otherwise power the cell. To understand the Krebs cycle, you must know what chemicals are involved in each step of the cycle and how they combine to produce the compounds of the next step.

Instructions

- 1
  Combine acetyl (CoA) with oxaloacetate to form a molecule of citrate. Acetyl is formed in the process just preceeding the Krebs cycle from pyruvate, which is the end product of glycolysis. Glycolysis means "sugar breaking" and involves breaking down a glycose molecule into pyruvates within the cell's cytoplasm. The acetyl is transported by acetyl coenzyme A. All of this takes place within the mitochondria.
- 2
  Remove H2O from the citrate molecule by taking away a hydroxyl group and a hydrogen molecule. These two carbons then join together through a double bond. Isocitrate is formed as a result.
- 3
  Oxidize the isocitrate molecule with a nicotinamide adenine dinucleotide (NAD) molecule. NAD is one of the most important coenzymes in the cell, used as an oxidizer. Bind the NAD with a hydrogen atom, which leaves a carbonyl group. A molecule of carbon dioxide (CO2) is then released, which produces alpha-ketoglutarate. The University of Illinois Department of Biology states that in the Krebs cycle, all carbon, hydrogen and oxygen in pyruvate end up as CO2 and water.
- 4
  Oxidize the alpha-ketoglutarate molecule. Reduce a molecule of NAD to form NADH (dehydrogenase). This will create instability in the process, releasing carbon dioxide and creating a molecule of succinyl-coenzyme.
- 5
  Remove a hydrogen atom from a water molecule within the Krebs cycle. The hydrogen atom bonds with coenzyme A. A free-floating phosphate group displaces this enzyme and bonds with the succinyl complex. Transfer this phosphate to a molecule of GDP (guanosine diphosphate). This produces an energy molecule of GTP (guanosine triphosphate) and leaves in its wake a molecule of succinate.
- 6
  Oxidize succinate with a molecule of FAD (flavin adenine dinucleotide). This creates fumarate.
- 7
  Add H2O to a fumarate molecule to form malate. This is accomplished by adding one hydrogen atom to a carbon atom by an enzyme and then adding a hydroxyl group to a carbon.
- 8
  Oxidize the malate molecule with an NAD molecule; the result is oxaloacetate. Combine the oxaloacetate with acetyl-coenzyme A. The Krebs cycle then repeats itself. The completion of the Krebs cycle results in the production of six NADH molecules, two FADH2 molecules, two ATP and four molecules of carbon dioxide.

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