Citric Acid Cycle: Difference between revisions
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*[[Krebs cycle overview]] | *[[Krebs cycle overview]] | ||
*[[Krebs cycle reactions]] | *[[Krebs cycle reactions]] | ||
*[[Major metabolic pathways converging on the citric acid cycle]] | |||
*[[Citric acid cycle intermediates serve as substrates for biosynthetic processes]] | |||
The [[Citric Acid Cycle]] (tricarboxylic acid cycle) is a series of enzyme catalyzed reactions which are critical in cellular respiration. Under oxidative conditions, pyruvate continues to be metabolized through the tricarboxylic acid cycle. In this cycle, Acetyl-CoA, a byproduct of [[glycolysis]], along with various cofactors, are broken down into carbon dioxide, water, and energy in the form of GTP and NADH. | The [[Citric Acid Cycle]] (tricarboxylic acid cycle) is a series of enzyme catalyzed reactions which are critical in cellular respiration. Under oxidative conditions, pyruvate continues to be metabolized through the tricarboxylic acid cycle. In this cycle, Acetyl-CoA, a byproduct of [[glycolysis]], along with various cofactors, are broken down into carbon dioxide, water, and energy in the form of GTP and NADH. | ||
[[Pyruvate dehydrogenase]] | '''Pyruvate decarboxylation or pyruvate oxidation''', also known as the link reaction (or oxidative decarboxylation of pyruvate), is the conversion of <scene name='39/392339/Cv1/11'>pyruvate</scene> into <scene name='43/430893/Cv/2'>Acetyl-CoA</scene> by the enzyme complex pyruvate dehydrogenase complex (see [[Pyruvate dehydrogenase]]). | ||
The multienzyme complex together catalyzes five distinct reactions in the conversion of pyruvate to | The multienzyme complex together catalyzes five distinct reactions in the conversion of pyruvate to Acetyl-CoA. The overall result is described by the following reaction: | ||
Pyruvate + CoA + NAD+ ==> Acetyl-CoA + CO2 + NADH | Pyruvate + CoA + NAD+ ==> Acetyl-CoA + CO2 + NADH | ||
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*Step 0 / 10 = [[Krebs cycle step 1]] | *Step 0 / 10 = [[Krebs cycle step 1]] | ||
*[[ATP-citrate synthase]] | *[[ATP-citrate synthase]] | ||
4C <scene name='43/430893/Cv/3'>oxaloacetate</scene> to a 6C molecule <scene name='43/430893/Cv/4'>citrate</scene> | |||
'''Step 1 - Dehydration - Aconitase''' | '''Step 1 - Dehydration - Aconitase''' | ||
* [[Aconitase]] | * [[Aconitase]] | ||
*1st step of [[Krebs cycle step 2]] | *1st step of [[Krebs cycle step 2]] | ||
6C Citrate => 6C <scene name='43/430893/Cv/5'>cis-Aconitate</scene> | |||
'''Step 2 - Hydration - Aconitase''' | '''Step 2 - Hydration - Aconitase''' | ||
* [[Aconitase]] | * [[Aconitase]] | ||
*2nd step of [[Krebs cycle step 2]] | *2nd step of [[Krebs cycle step 2]] | ||
6C ''cis''-Aconitate => 6C <scene name='43/430893/Cv/6'>Isocitrate</scene> | |||
'''Step 3 - Oxidation - Isocitrate dehydrogenase''' | '''Step 3 - Oxidation - Isocitrate dehydrogenase''' | ||
*[[Isocitrate dehydrogenase]] | *[[Isocitrate dehydrogenase]] | ||
*1st step of [[Krebs cycle step 3]] | *1st step of [[Krebs cycle step 3]] | ||
6C Isocitrate => 6C <scene name='43/430893/Cv/7'>Oxalosuccinate</scene> | |||
'''Step 4 - Decarboxylation - Isocitrate dehydrogenase''' | '''Step 4 - Decarboxylation - Isocitrate dehydrogenase''' | ||
*[[Isocitrate dehydrogenase]] | *[[Isocitrate dehydrogenase]] | ||
*2nd step of [[Krebs cycle step 3]] | *2nd step of [[Krebs cycle step 3]] | ||
6C Oxalosuccinate => 5C <scene name='43/430893/Cv/8'>α-Ketoglutarate</scene> | |||
The α-ketoglutarate family of amino acid synthesis (synthesis of glutamate, glutamine, proline and arginine) begins with α-ketoglutarate, an intermediate in the Citric Acid Cycle. See [[Alpha-Ketoglutarates: glutamate, glutamine, proline, arginine]] | |||
'''Step 5 - Oxidative decarboxylation - α-Ketoglutarate dehydrogenase (2-Oxoglutarate Dehydrogenase)''' | '''Step 5 - Oxidative decarboxylation - α-Ketoglutarate dehydrogenase (2-Oxoglutarate Dehydrogenase)''' | ||
*[[2-Oxoglutarate Dehydrogenase]] | *[[2-Oxoglutarate Dehydrogenase]] | ||
*Step 5 = [[Krebs cycle step 4]] | *Step 5 = [[Krebs cycle step 4]] | ||
5C α-Ketoglutarate => <scene name='43/430893/Cv/9'>Succinyl-CoA</scene> 4C chain (CoA excluded) | |||
'''Step 6 - Substrate-level phosphorylation - Succinyl-CoA synthetase''' | |||
* [[ | *[[Succinyl-CoA synthetase]] | ||
*Step 6 = [[Krebs cycle step 5]] | |||
* [[ | Succinyl-CoA => <scene name='43/430893/Cv/10'>Succinate</scene> | ||
* [[ | |||
The succinyl-CoA formed during [[Beta oxidation]] can also enter the Citric Acid Cycle in this step. | |||
* [[ | |||
* [[ | '''Step 7 - Oxidation - Succinate dehydrogenase''' | ||
* [[Malate dehydrogenase | *[[Succinate Dehydrogenase]] | ||
* [[ | *Step 7 = [[Krebs cycle step 6]] | ||
Succinate => <scene name='43/430893/Cv/11'>Fumarate</scene> | |||
'''Step 8 - Hydration - Fumarase''' | |||
*[[Fumarase]] | |||
*Step 8 = [[Krebs cycle step 7]] | |||
Fumarate => <scene name='43/430893/Cv/12'>L-Malate</scene> | |||
'''Step 9 - Oxidation - Malate dehydrogenase''' | |||
*[[Malate dehydrogenase]] | |||
*Step 9 = [[Krebs cycle step 8]] | |||
L-Malate => <scene name='43/430893/Cv/3'>oxaloacetate</scene> | |||
Oxaloacetate takes part in [[gluconeogenesis]], the urea cycle, the glyoxylate cycle, amino acid synthesis ([[Oxaloacetate/aspartate: lysine, asparagine, methionine, threonine, and isoleucine]]), [[fatty acid synthesis]]. | |||
'''Step 10 / 0 - Aldol condensation - Citrate synthase''' | |||
* [[ | *[[Citrate Synthase]] | ||
< | *Step 10 / 0 = [[Krebs cycle step 1]] | ||
4C <scene name='43/430893/Cv/3'>oxaloacetate</scene> to a 6C molecule <scene name='43/430893/Cv/4'>citrate</scene> | |||
To view automatically seeded indices concerning [[Citric Acid Cycle]] See: | To view automatically seeded indices concerning [[Citric Acid Cycle]] See: | ||
*[[:Category:Citric acid cycle|Citric Acid Cycle]] | *[[:Category:Citric acid cycle|Citric Acid Cycle]] | ||
<br /> | <br /> | ||
See also: | |||
*[[Biosynthesis of cholesterol]] | |||
*[[Fatty acid synthesis]] | |||
*[[Amino Acid Synthesis]] | |||
</StructureSection> | </StructureSection> | ||