Citric Acid Cycle Quiz

The process of breaking down pyruvate into carbon dioxide, water, and energy (ATP) in the form of NADH and FADH2.

The Citric Acid Cycle is also known as the Krebs Cycle and the TCA cycle.

The Citric Acid Cycle is a cyclic series of reactions that oxidizes acetyl-CoA to CO2 and H2O, generating energy in the form of ATP, NADH, and FADH2.

The Citric Acid Cycle is a central metabolic pathway, linking catabolic and anabolic pathways, meaning it can both break down and build up molecules.

The Citric Acid Cycle is regulated by both allosteric and covalent mechanisms to control its activity in coordination with other pathways in the cell.

The Citric Acid Cycle generates ATP, NADH, and FADH2, which are crucial for energy production in the cell.

The Citric Acid Cycle is closely linked to glycolysis, with pyruvate as the key intermediate that connects the two pathways.

Enzymes in the Citric Acid Cycle work together in a complex to efficiently catalyze a series of reactions, ensuring smooth and efficient energy production.

An irreversible oxidation process that removes the carboxyl group (COOH) from a molecule, releasing carbon dioxide (CO2) as a byproduct.

The pyruvate dehydrogenase complex (PDH) is a group of enzymes that catalyzes the conversion of pyruvate to acetyl-CoA. It is a key step in cellular respiration, linking glycolysis to the citric acid cycle.

Lipoate is a coenzyme that acts as both an electron and acyl carrier. It's attached to the E2 enzyme in the PDH complex.

Thiamine pyrophosphate (TPP) is a coenzyme derived from vitamin B1 (thiamine) and is essential for the activity of the PDH complex.

Coenzyme A (CoA) is a coenzyme derived from pantothenic acid (vitamin B5) and plays a crucial role in the PDH complex by carrying acetyl groups.

Flavin adenine dinucleotide (FAD) is a coenzyme derived from riboflavin (vitamin B2) and is essential for the activity of the PDH complex.

Nicotinamide adenine dinucleotide (NAD) is a coenzyme derived from niacin (vitamin B3) and is essential for the activity of the PDH complex.

Enzymes often assemble into complexes to enhance efficiency. This strategy, seen in the PDH complex, allows for a series of reactions to occur smoothly without intermediates escaping into the cell.

An enzyme in the citric acid cycle that catalyzes the conversion of succinyl-CoA to succinate, generating ATP (or GTP) through substrate-level phosphorylation.

A chemical reaction in metabolism where ATP is produced directly from an energy-rich substrate, without the need for an electron transport chain.

A component of the citric acid cycle that catalyzes the oxidation of succinate to fumarate, using FAD as an electron acceptor.

A potent competitive inhibitor of succinate dehydrogenase, structurally similar to succinate but unable to be metabolized.

The reaction in the citric acid cycle where FADH2 is produced, catalyzed by succinate dehydrogenase.

An enzyme in the citric acid cycle that catalyzes the reversible hydration of fumarate to L-malate.

The last step in the citric acid cycle where L-malate is oxidized to oxaloacetate, regenerating the starting compound for the cycle.

The enzyme that catalyzes the oxidation of L-malate to oxaloacetate, using NAD+ as an electron acceptor.

The Citric Acid Cycle is a central metabolic pathway that plays a crucial role in cellular respiration, not just energy conservation. It involves the breakdown of acetyl-CoA to generate energy carriers like NADH, FADH2, and ATP.

In the first turn of the Citric Acid Cycle, the carbon atoms from acetyl-CoA do not leave the cycle as CO2. They are incorporated into other molecules and will eventually be released in subsequent turns.

The Citric Acid Cycle takes place in the mitochondria of eukaryotic cells. The mitochondria are often referred to as the 'powerhouses' of the cell.

The Citric Acid Cycle begins with the condensation reaction of acetyl-CoA and oxaloacetate, catalyzed by citrate synthase. This step involves the formation of a transient intermediate called citroyl-CoA.

The conversion of the relatively unreactive methyl group of acetyl-CoA to a more reactive methylene group is a crucial step in the Citric Acid Cycle. This conversion is essential for the subsequent oxidation reactions.

The large, negative ΔG'° value of the citrate synthase reaction is driven by the low concentration of oxaloacetate. This ensures the reaction proceeds in the forward direction.

Citrate synthase is an enzyme that undergoes a conformational change upon binding oxaloacetate. This creates a binding site for acetyl-CoA, promoting the formation of citroyl-CoA.

The Citrate synthase reaction involves acid-base catalysis. This mechanism utilizes acidic and basic amino acid residues in the enzyme's active site to facilitate the reaction.

A metabolic pathway that serves both catabolic and anabolic processes. It breaks down molecules for energy but also builds new molecules for growth and repair. An example is the citric acid cycle.

A metabolic pathway involved in the catabolism of carbohydrates, fatty acids, and proteins. It generates energy through the oxidation of acetyl-CoA.

A metabolic pathway found in plants, bacteria, and fungi that conserves carbon dioxide during the breakdown of fatty acids. This allows the organism to produce more glucose.

The glyoxylate cycle conserves carbon dioxide, whereas the citric acid cycle releases it as a waste product. This allows the glyoxylate cycle to produce glucose from fatty acids.

Biochemical reactions that replenish intermediates of the citric acid cycle, allowing the cycle to continue operating efficiently.

An enzyme that catalyzes the conversion of pyruvate to oxaloacetate, replenishing an important intermediate of the citric acid cycle.

An enzyme that catalyzes the conversion of phosphoenolpyruvate (PEP) to oxaloacetate, another important anaplerotic reaction.

An enzyme involved in the conversion of succinyl-CoA to oxaloacetate, another anaplerotic reaction that replenishes the citric acid cycle.

Mutations in succinate dehydrogenase or fumarase, two key enzymes in the Citric Acid Cycle, can disrupt the cycle and lead to the abnormal growth of cells, causing tumors. This makes these mutated enzymes act as tumor suppressors.

NADPH-dependent isocitrate dehydrogenase is an enzyme that converts isocitrate to α-ketoglutarate in the Citric Acid Cycle. Mutations in this enzyme can cause tumors by changing its function, leading to the production of 2-hydroxyglutarate, disrupting the normal cell processes.

Metabolons are multienzyme complexes that work together in a coordinated way, ensuring that the products of one enzyme reaction are quickly and efficiently passed on to the next enzyme in the pathway. This creates a smoothly functioning metabolic "machine."

Malate dehydrogenase, citrate synthase, and aconitase are important enzymes in the Citric Acid Cycle. These three enzymes likely work together as a metabolon, forming a coordinated complex that enhances the efficiency of the Citric Acid Cycle.

Metabolons are multienzyme complexes, providing direct and efficient pathways for metabolic intermediates, ensuring a smooth flow of reactions within a metabolic pathway.