Citric Acid Cycle

The citric acid cycle — also known as the tricarboxylic acid cycle (TCA cycle), the Krebs cycle, or the Szent-Györgyi–Krebs cycle — is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and proteins into carbon dioxide. In addition, the cycle provides precursors including certain amino acids as well as the reducing agent NADH that is used in numerous biochemical reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism and may have originated abiogenically.

The name of this metabolic pathway is derived from citric acid (a type of tricarboxylic acid) that is first consumed and then regenerated by this sequence of reactions to complete the cycle. In addition, the cycle consumes acetate (in the form of acetyl-CoA) and water, reduces NAD+ to NADH, and produces carbon dioxide. The NADH generated by the TCA cycle is fed into the oxidative phosphorylation pathway. The net result of these two closely linked pathways is the oxidation of nutrients to produce usable energy in the form of ATP.

In eukaryotic cells, the citric acid cycle occurs in the matrix of the mitochondrion. Bacteria also use the TCA cycle to generate energy, but since they lack mitochondria, the reaction sequence is performed in the cytosol with the proton gradient for ATP production being across the plasma membrane rather than the inner membrane of the mitochondrion.

The components and reactions of the citric acid cycle were established in the 1930s by seminal work from the Nobel laureates Albert Szent-Györgyi and Hans Adolf Krebs.

Read more about Citric Acid CycleEvolution, Overview, Steps, Products, Regulation, Major Metabolic Pathways Converging On The TCA Cycle, Interactive Pathway Map

Other articles related to "acid, citric acid cycle, cycle, citric acid, acid cycle":

Amino Acid Synthesis - Amino Acid Biosynthesis Is Regulated By Feedback Inhibition - Additional Regulation Based On Amino Acid Families - α-ketoglutarate Family
... A 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 ... the condensation reaction initiating the Citric Acid Cycle is strongly inhibited by α-ketoglutarate feedback inhibition and can be inhibited by DPNH ... This is one of the initial regulations of the α-ketoglutarate family of amino acid synthesis ...
Mitochondrial Matrix - Citric Acid Cycle
... The citric acid cycle (or Krebs cycle or TCA cycle) takes place within the mitochondrial matrix ... Prior to the citric acid cycle, pyruvic acid generated from glycolysis is converted into acetyl coenzyme A (acetyl CoA) by losing a carbon dioxide molecule ... It then combines with oxaloacetic acid to form citric acid (a six-carbon molecule) to begin the citric acid cycle ...
Carbon Fixation - Other Autotrophic Pathways - Reductive Citric Acid Cycle
... The reductive citric acid cycle is the oxidative citric acid cycle run in reverse ... The reductive citric acid cycle is sometimes called the Arnon-Buchanan cycle ...
Plant Respiration - Aerobic Respiration - Citric Acid Cycle
... This is also called the Krebs cycle or the tricarboxylic acid cycle ... aerobic respiration which leads to the Krebs cycle ... is produced, the molecule then enters the citric acid cycle (Krebs cycle) inside the mitochondrial matrix, and gets oxidized to CO2 while at the same time reducing NAD to NADH ...

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