Chapter 17b - The Citric Acid Cycle

Citrate Synthase

An enzyme that catalyzes the condensation of acetyl-CoA & oxaloacetate to form citrate. (large, -∆G)

Isocitrate Dehydrogenase

An enzyme that catalyzes the oxidative decarboxylation of isocitrate to form α-ketoglutarate, producing NADH. (links CAC to ETC)

A-Ketoglutarate Dehydrogenase

An enzyme that catalyzes the oxidative decarboxylation of α-ketoglutarate to succinyl-CoA, producing NADH & CO2.

Succinyl-CoA Synthetase

An enzyme that catalyzes substrate level phosphorylation of succinyl-CoA to succinate, coupled w/ the phosphorylation of GDP to GTP (or ADP to ATP)

Succinate Dehydrogenase

An enzyme that catalyzes the oxidation of succinate to fumarate, producing FADH2 (Links CAC to ETC)

Fumarase

An enzyme that catalyzes the reversible hydration of fumarate to malate by adding water across the double bond of fumarate

Malate Dehydrogenase

An enzyme that catalyzes the oxidation of malate to oxaloacetate, producing NADH in the process.

Prochiral

A molecule that can be converted into a chiral molecule by a single chemical change. (helps us understand enzyme specificity & reaction mechanisms)

Pyruvate Dehydrogenase Kinase

An enzyme that phosphorylates & inactivates pyruvate dehydrogenase, reducing the conversion of pyruvate to acetyl-CoA.

Arsenite Poisoning

A toxic condition caused by exposure to arsenite, which inhibits enzymes like pyruvate dehydrogenase, affecting energy metabolism.

Anaplerotic

Refers to reactions that replenish intermediates of metabolic cycles. (Maintains the balance of intermediates needed for energy production)

Glycoxylate Cycle

A modified version of the citric acid cycle found in plants, bacteria, & fungi, which enables the conversion of fatty acids into glucose.

PEP Carboxylase

Converts PEP to Oxaloacetate

Pyruvate Carboxylase

Converts pyruvate to oxaloacetate

Malic Enzyme

Converts pyruvate to malate

Isocitrate Lyase

Produces glyoxylate & succinate

Aconitase

A mitochondrial enzyme that catalyzes the isomerization of citrate to isocitrate through a two-step process in the citric acid cycle.

Reductive TCA Cycle

Citric Acid Cycle where some of the reactions run in reverse, leading to the reduction of carbon dioxide & the synthesis of organic compounds like acetyl-CoA.