The Common Catabolic Pathway: Citric Acid Cycle, the Electron Transport Chain, and ATP Biosynthesis

Flashcards about the Citric Acid Cycle, Electron transport chain and ATP Biosynthesis

What is the main function of the Citric Acid Cycle?

Serves as a central metabolic hub, generating 2 CO2, 1 GTP or ATP, 3 NADH/H+, and 1 FADH2.

What is a metabolon?

A group of enzymes performing reactions with a common purpose, often localized in an organelle.

What is substrate channeling?

The diversion of the product of one enzymatic reaction directly into a subsequent reaction, increasing reaction rate and efficiency.

What is the role of Acetyl-CoA?

Important intermediate in several pathways, including fatty acid catabolism, containing energetically rich chemical bonds.

What is the function of Citrate Synthase?

Catalyzes the condensation of acetyl CoA with oxaloacetate to produce citrate.

What role does Aconitase play in the Citric Acid Cycle?

Catalyzes the reversible isomerization of citrate to isocitrate.

What is the function of Isocitrate Dehydrogenase?

Catalyzes the oxidation of isocitrate to α-ketoglutarate, reducing NAD+.

What reaction does α-Ketoglutarate Dehydrogenase catalyze?

Oxidizes α-ketoglutarate to succinyl-CoA and is the rate-determining step, reducing NAD+.

What are the three subunits of the α-Ketoglutarate Dehydrogenase Complex?

E1—TPP decarboxylase, E2—dihydrolipoyl transferase, and E3—dihidyrolipoyl dehydrogenase

What is the function of Succinyl CoA Synthetase?

Catalyzes substrate-level phosphorylation generating succinate and ATP or GTP.

What occurs during transamination reactions?

Amine groups are shuttled to α-ketoglutarate to generate glutamate and a new α-keto acid from the old amino acid.

What is the function of ATP Synthase?

Multimeric enzyme that uses electro-chemical energy from the proton gradient to produce ATP from ADP and Pi

What is Proton Motive Force?

Electrochemical potential derived from the uneven distribution of electrons across the inner mitochondrial matrix.

What is the function of Succinate Dehydrogenase?

Catalyzes the stereospecific reduction of fumarate to succinate.

Describe the role of Fumarase in the Citric Acid Cycle.

Catalyzes the hydration of fumarate to form L-malate.

What is the function of Malate Dehydrogenase?

Catalyzes the oxidation of malate to oxaloacetate, reducing NAD+.

How is the Citric Acid Cycle regulated?

Regulated at strongly exergonic steps: citrate synthase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase.

What is the effect of ATP and NADH on the Citric Acid Cycle?

ATP and NADH are allosteric inhibitors, slowing the cycle when energy is plentiful.

What is the effect of AMP on the Citric Acid Cycle?

AMP allosterically activates isocitrate dehydrogenase, speeding up the cycle when energy is low.