Citric acid cycle

Definition

The citric acid cycle—also known as the Krebs cycle, Szent–Györgyi–Krebs cycle, or TCA cycle —is a series of biochemical reactions that release the energy stored in nutrients through acetyl-CoA oxidation. The energy released is available in the form of ATP. The Krebs cycle is used by organisms that generate energy via respiration, either anaerobically or aerobically. In addition, the cycle provides precursors of certain amino acids, as well as the reducing agent NADH, which are used in other reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest metabolic components. Even though it is branded as a "cycle", it is not necessary for metabolites to follow a specific route; at least three alternative pathways of the citric acid cycle are recognized.

Related concepts

2-hydroxyglutarate 5-Methylcytosine ACO2 ATP citrate lyase ATP synthase Abiogenesis Acetate Acetobacter aceti Acetone–butanol–ethanol fermentation Acetyl Acetyl-CoA Acetyl-CoA carboxylase Acetyl-coA Acetyl CoA Aconitase Aconitate Aconitic acid Active transport Acyl-CoA Adenosine diphosphate Adenosine monophosphate Adenosine triphosphate Aerobic respiration Alanine Albert Szent-Györgyi Aldol condensation Allosteric Alpha-Ketoglutaric acid Alpha-ketoglutarate dehydrogenase Alpha ketoglutarate Alternative oxidase Amino acid Amino acid metabolism Amino acid synthesis Amino sugar Aminolevulinic acid Amphibolic Anabolic Anabolism Anaerobic bacteria Anaerobic respiration Anaplerotic reactions Angiogenesis Animal cells Anoxygenic photosynthesis Antioxidant Apoptosis Arginine Aromatic amino acid Ascorbate Asparagine Aspartate Aspartate transaminase Aspartic acid Bacteria Beta-oxidation Beta oxidation Bile acid Bile acids Bile pigment Bioenergetics Bioinorganic chemistry Biosynthesis Branched-chain amino acid COQ10A COQ10B COQ2 COQ4 COQ6 COQ7 COQ9 Calciferol Calvin cycle Cancer Carbohydrate Carbohydrate catabolism Carbohydrate metabolism Carbon Carbon dioxide Carbon fixation Carboxyl Carboxylated Carotenoid Catabolic Catabolism Cell growth Cell membrane Cell migration Cell signaling Cellular respiration Chemical reaction Chemiosmosis Chemosynthesis Chlorophyll Chlororespiration Cholesterol Cis–trans isomerism Citrate Citrate synthase Citric acid Cobalamin Coenzyme A Coenzyme Q Coenzyme Q10 Coenzyme Q5, methyltransferase Coenzyme Q – cytochrome c reductase Cofactor (biochemistry)Competitive inhibition Complex III Condensation reaction Convergent evolution Cori cycle Creatine Cytidine triphosphate Cytochrome Cytochrome c Cytochrome c oxidase Cytoplasm Cytosine Cytosol D2HGDH DLST DNA DNA replication DeLey-Doudoroff pathway Deamination Decarboxylation Dehydration reaction Dihydrolipoamide dehydrogenase Dihydrolipoyl transacetylase Dihydroxyacetone phosphate Dioxygenase Disaccharide E3 ubiquitin ligase Eicosanoid Eicosanoid metabolism Electron-transferring-flavoprotein dehydrogenase Electron transport chain Endocannabinoid system Entner-Doudoroff pathway Enzyme Enzymes Epinephrine Epithelial–mesenchymal transition Erythrose 4-phosphate Essential amino acid Ethanol fermentation Ethanol metabolism Eukaryote Eukaryotic cell Fat Fat catabolism Fatty acid Fatty acid degradation Fatty acid metabolism Fatty acid synthesis Fatty acids Fermentation Flavin adenine dinucleotide Fructolysis Fructose 1,6-bisphosphate Fumarase Fumarate Fumaric acid Gain-of-function mutation Galactolysis Glucagon Glucogenic amino acid Gluconeogenesis Glucose Glucose 6-phosphate Glutamate Glutamate dehydrogenase Glutamic acid Glutamine Glutathione Glycan Glyceraldehyde-3-phosphate Glyceraldehyde 3-phosphate Glycerol Glycerol 3-phosphate Glycerol phosphate shuttle Glycerolipid Glycerophospholipid Glycogenesis Glycogenolysis Glycolysis Glycoprotein Glycosphingolipid Glycosylation Glyoxylate cycle Glyoxylic acid Guanosine diphosphate Guanosine triphosphate HIF1A Hans Adolf Krebs Helicobacter pylori Heme Hemoglobin Hemoprotein Heterozygous Hexaprenyldihydroxybenzoate methyltransferase Histidine Histone code Homeostasis Homoserine Human iron metabolism Hydration reaction Hydrolysis Hydroxylation Hypoxia-inducible factors IDH2 IDH3A IDH3B IDH3G Inner membrane of the mitochondrion Inorganic phosphate Inositol phosphate Interstellar medium Isocitrate Isocitrate dehydrogenase Isocitric acid Isoleucine Isomerization Isopentenyl pyrophosphate KEGG Keto acid Ketogenesis Ketogenic amino acid Ketone bodies Ketosis Kidney L2HGDH Lactic acid Lactic acid fermentation Leloir pathway Leucine Light-dependent reactions Lipid metabolism Lipogenesis Lipoic acid Lipolysis Liver Lysine Malate Malate dehydrogenase Malate dehydrogenase 2 Malate–aspartate shuttle Malic acid MetaCyc Metabolic Metabolic network Metabolic pathway Metabolism Metabolite Metalloprotein Methylene bridge Methylerythritol phosphate Methylmalonyl-CoA mutase Mevalonate pathway Mevalonic acid Mitochondrial disease Mitochondrial matrix Mitochondrion Molar equivalent Molecules Monosaccharide Muscle tissue Myoglobin N-linked glycosylation NADH NADH dehydrogenase NADPH Neomorphic mutation Neoplasm Neurotransmitters Nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide phosphate Nobel Prize for Physiology or Medicine Nobel Prize in Physiology or Medicine Non-mevalonate pathway Nucleic acid Nucleic acid metabolism Nucleoside-diphosphate kinase Nucleotide Nucleotide salvage Nucleotide sugar Nutrient O-linked glycosylation OGDH Oncogene Oncology Oncometabolism Organic redox reaction Organism Oxaloacetate Oxaloacetic acid Oxalosuccinate Oxalosuccinic acid Oxidation Oxidative phosphorylation Oxidative stress Oxoglutarate dehydrogenase complex PDSS1 PDSS2 Pentose phosphate pathway Persulfate Phenylalanine Phosphagen Phosphate Phosphoenolpyruvate Phosphoenolpyruvate carboxykinase Phosphofructokinase Phosphoglycerate Phosphoribosyl pyrophosphate Phosphorylation Photorespiration Photosynthesis Photosystem Plant cell Polyamine Polyketide Polyol pathway Polysaccharide Polyunsaturated fatty acid Porphyrin Precursor (chemistry)Primary nutritional groups Prokaryotic cell Proline Prolyl hydroxylase Propionyl-CoA Prosthetic group Protease Protein Protein biosynthesis Protein catabolism Protein complex Protein metabolism Proteoglycan Proteolysis Pseudohypoxia Purine metabolism Purine nucleotide cycle Purines Pyridoxine Pyrimidine metabolism Pyrimidines Pyruvate Pyruvate carboxylase Pyruvate decarboxylation Pyruvate dehydrogenase Pyruvate dehydrogenase complex Pyruvate dehydrogenase kinase Pyruvate dehydrogenase phosphatase Pyruvic acid Quinone RNA Radiosynthesis (metabolism)Redox Reducing agent Retinoid Reverse Krebs cycle Reverse cholesterol transport Ribose 5-phosphate SDHA SDHB SDHD SUCLA2 SUCLG1 SUCLG2 Serine Shikimate pathway Shikimic acid Sialic acid Skeletal formula Smith College Sphingolipid Sphingolipid metabolism Steroid Striated muscle tissue Substrate-level phosphorylation Succinate Succinate dehydrogenase Succinate dehydrogenase complex subunit C Succinate semialdehyde Succinic acid Succinyl-CoA Succinyl coenzyme A synthetase Sugar acid Synthase Ten-Eleven Translocation 2 Terpenoid Thiamine pyrophosphate Thymine Thyroid hormone Tissue (biology)Tocopherol Trans-2-enoyl-CoA reductase (NADPH)Transamination Transcription (genetics)Transcription factor Transit map Translation (biology)Tricarboxylic acid Triglyceride Tryptophan Tumorigenesis Tyrosine Ubiquinol Ubiquinone University of Sheffield Uracil Urea cycle Uridine diphosphate Uridine monophosphate Uridine triphosphate Vascular remodelling in the embryo Vitamin Vitamin A Vitamin B Vitamin C Vitamin D Vitamin E Vitamin K Von Hippel Lindau Warburg effect (oncology)Water Wax William Arthur Johnson (biochemist)Xylose metabolism Α-Ketoglutaric acid

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