Chapter 17. The Citric Acid Cycle Flashcards
proteins that contain clusters of iron and sulfur that play a role in electron transfer reactions; iron cycles between the Fe2+ and Fe3+ state.
Iron-sulfur (nonheme iron) protein
proteins tightly associated with FAD or FMN. Flavoproteins play important roles in many oxidation-reduction reactions.
Flavoprotein
A cyclic series of metabolic reactions that completely oxidize acetyl units to carbon dioxide. Also known as the tricarboxylic acid cycle (after citrate) or the Krebs cycle, after Hans Krebs, who elucidated the cyclic nature of the pathway.
Citric acid (tricarboxylic acid, TCA; Krebs) cycle
the enzyme that catalyzes the condensation of acetyl CoA with oxaloacetate to form citrate, initiating the citric acid cycle.
Citrate synthase
An enzyme that catalyzes the ATP-dependent synthesis of malonyl CoA from acetyl CoA and carbon dioxide, the committed step in fatty acid synthesis.
Acetyl CoA
From the Greek for “fill up,” referring to a reaction that replenishes intermediates removed from a metabolic pathway. The most common example is the reaction catalyzed by pyruvate carboxylase, in which the carboxylation of pyruvate produces oxaloacetate, a key component of the citric acid cycle.
Anaplerotic reaction
a neurologic and cardiovascular disorder caused by a dietary deficiency of thiamine (vitamin B1).
Beriberi
a metabolic pathway that converts two- carbon units into succinate for energy production and biosyntheses; found primarily in bacteria and plants, the cycle bypasses two decarboxylation steps in the citric acid cycle and allows net formation of glucose and other molecules via oxaloacetate from acetate or acetyl CoA.
Glyoxylate cycle
plant organelles in which enzymes of the glyoxylate pathway are present.
glyoxysome
the enzyme that catalyzes the oxidative decarboxylation of isocitrate to form α-ketoglutarate. Isocitrate dehydrogenase plays a role in controlling the rate of the citric acid cycle.
Isocitrate dehydrogenase
the process in which ATP is formed as the result of the transfer of electrons from NADH or FADH2 to O2 via a series of electron carriers.
Oxidative phosphorylation
a large, complex mitochondrial enzyme that catalyzes the oxidative decarboxylation of pyruvate to form acetyl CoA. This irreversible reaction is the link between glycolysis and the citric acid cycle.
Pyruvate dehydrogenase complex
the citric acid cycle enzyme that catalyzes the oxidative decarboxylation of alpha-ketoglutarate to yield succinyl CoA. This enzyme, which helps to regulate the rate of the citric acid cycle, is structurally and mechanistically similar to the pyruvate dehydrogenase complex.
α-ketoglutarate dehydrogenase
an enzyme of the glyoxylate cycle that cleaves isocitrate into succinate and glyoxylate
Isocitrate lyase
An enzyme of the glyoxylate cycle that catalyzes the formation of oxaloacetate from glyoxylate and acetyl CoA.
Malate synthase
