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The Citric Acid Cycle definitions

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  • Citrate
    A six-carbon molecule formed from acetyl CoA and oxaloacetate, marking the entry point into the cycle.
  • Oxaloacetate
    A four-carbon molecule regenerated at the end of the cycle, enabling continuous operation by combining with acetyl CoA.
  • Acetyl CoA
    A two-carbon molecule attached to coenzyme A, serving as the primary input for the cycle.
  • Citrate Synthase
    An enzyme catalyzing the initial condensation of acetyl CoA and oxaloacetate to form citrate.
  • Aconitase
    An enzyme responsible for isomerizing citrate to isocitrate, enabling subsequent oxidation.
  • Isocitrate
    A rearranged form of citrate with a secondary alcohol, making it suitable for oxidation.
  • Alpha Ketoglutarate
    A five-carbon intermediate produced by oxidation and decarboxylation of isocitrate.
  • Succinyl CoA
    A four-carbon compound with a high-energy thioester bond, formed after decarboxylation of alpha ketoglutarate.
  • Succinate
    A four-carbon molecule generated from succinyl CoA, linked to substrate-level phosphorylation.
  • Fumarate
    A four-carbon dicarboxylate formed by oxidation of succinate, featuring a trans double bond.
  • Malate
    A four-carbon hydroxy acid produced by hydration of fumarate, later oxidized to regenerate oxaloacetate.
  • NADH
    A high-energy electron carrier generated during oxidation steps, crucial for ATP production in the electron transport chain.
  • FADH2
    An electron carrier produced during succinate oxidation, contributing electrons to the electron transport chain.
  • ATP
    A universal energy currency synthesized directly in the cycle via substrate-level phosphorylation.
  • Decarboxylation
    A reaction type in the cycle where a carbon atom is removed as carbon dioxide, reducing the carbon count of intermediates.