20 citric acid cycle

These flashcards cover key vocabulary and concepts related to the citric acid cycle in biochemistry, including processes, enzymes, and regulations.

Citric Acid Cycle

A metabolic pathway that extracts energy from carbohydrates, lipids, proteins, and other metabolites through the oxidation of acetyl-CoA.

Acetyl-CoA

A central molecule in metabolism that provides entry into the citric acid cycle.

Aerobic Conditions

Conditions in which oxygen is present, allowing for the citric acid cycle to occur.

GTP/ATP

A high-energy molecule produced during the citric acid cycle, allowing for energy transfer in cellular processes.

Electron Transport Chain

A series of complexes that transfer electrons to generate ATP through oxidative phosphorylation.

NADH

A reduced electron carrier that transports electrons to the electron transport chain.

FADH2

Another reduced electron carrier that donates electrons to the electron transport chain.

Amphibolic Pathway

A metabolic pathway that participates in both catabolism and anabolism.

Oxidative Phosphorylation

The process by which ATP is produced from ADP and inorganic phosphate using energy derived from electrons transferred through the electron transport chain.

Citrate Synthase

An enzyme that catalyzes the first step of the citric acid cycle by converting acetyl-CoA and oxaloacetate to citrate.

Aconitase

An enzyme that isomerizes citrate to isocitrate by a two-step dehydration-hydration process.

Isocitrate Dehydrogenase

An enzyme that catalyzes the first energy-harvesting step in the citric acid cycle, converting isocitrate to α-ketoglutarate.

α-Ketoglutarate Dehydrogenase

An enzyme that catalyzes the oxidative decarboxylation of α-ketoglutarate to succinyl-CoA.

Succinyl-CoA Synthetase

An enzyme that catalyzes the conversion of succinyl-CoA into succinate while producing GTP or ATP.

Succinate Dehydrogenase

An enzyme that oxidizes succinate to fumarate, transferring electrons to FAD.

Fumarase

An enzyme that stereospecifically converts fumarate to malate.

Malate Dehydrogenase

An enzyme that catalyzes the oxidation of malate to oxaloacetate, regenerating this substrate for the cycle.

Standard Free Energy Change (ΔG°′)

A measure of the energy change in a reaction, indicating spontaneity.

Redox Reactions

Chemical reactions that involve the transfer of electrons between reactants.

Regulation of the Citric Acid Cycle

The control of enzyme activities via substrate availability, allosteric regulation, and feedback inhibition.

Anaplerotic Reactions

Reactions that replenish the intermediates of the citric acid cycle.

Cataplerotic Processes

Reactions that deplete the intermediates of the citric acid cycle.

Malate-Aspartate Shuttle

A mechanism for transferring electrons from cytosolic NADH into the mitochondrial electron transport chain.

Glycerophosphate Shuttle

A system that transfers electrons from cytosolic NADH to the electron transport chain with a slight energy loss.

Oxaloacetate

A four-carbon molecule that combines with acetyl-CoA at the beginning of the citric acid cycle.

Electron Carriers

Molecules like NADH and FADH2 that carry electrons to the electron transport chain.

Intermediates

Substances formed during the steps of a biochemical process, such as the citric acid cycle.

High Energy Intermediates

Molecules that store energy temporarily, such as GTP and ATP.

Hydrolysis of Succinyl-CoA

A reaction that releases energy used to drive the formation of GTP or ATP.

Free Energy Change

Energy difference that governs the direction and spontaneity of chemical reactions.

Compartmentalization

The separation of different biochemical processes in cellular compartments to enhance metabolic efficiency.

Energy Harvesting Steps

Key reactions in the citric acid cycle that produce reduced electron carriers and high-energy molecules.