TCA cycle

• What is the primary role of the TCA cycle in metabolism?

  Final pathway for oxidative metabolism

  
• What types of macromolecules converge in the TCA cycle?

  Carbohydrates, proteins, and fats
• What is produced from the carbon skeletons in the TCA cycle?

  CO2
• How does the TCA cycle relate to the body's catabolic pathways?

  Most catabolic pathways converge on TCA cycle
• What does the TCA cycle provide for amino acid synthesis?

  Building blocks for some amino acids
• Is the TCA cycle a closed circle?

  No, it is a traffic circle
• What is the primary energy product of the TCA cycle?

  ATP

  
• Why is the TCA cycle considered an aerobic pathway?

  O2 is required as the final electron acceptor
• Where does the TCA cycle occur in the cell?

  In the mitochondria
• What is the first step of the TCA cycle?

  Synthesis of citrate from acetyl CoA and oxaloacetate

  
• What is the product of the oxidative decarboxylation of pyruvate?

  Acetyl CoA
• What enzyme catalyzes the conversion of pyruvate to acetyl CoA?

  Pyruvate dehydrogenase complex

  
• Is the conversion of pyruvate to acetyl CoA reversible?

  No, it is an irreversible process
• What is the role of the PDH complex in the TCA cycle?

  Major source of acetyl CoA

  
• What are the components of the PDH complex?

  Three enzymes: E1, E2, E3

  
• What coenzyme does E1 of the PDH complex require?

  Thiamine pyrophosphate (TPP)

  
• What happens if there is a deficiency of thiamine?

  Serious CNS problems due to ATP deficiency
• How does PDH complex regulation occur?

  Through phosphorylation and dephosphorylation

  
• What activates PDH kinase?

  High-energy signals like ATP and NADH
• What is the effect of elevated pyruvate levels on PDH complex?

  Inhibits PDH kinase, activating E1

  
• What role does calcium play in PDH regulation?

  Activates PDH phosphatase, stimulating E1
• What is the consequence of pyruvate dehydrogenase deficiency?

  Congenital lactic acidosis
• What are the symptoms of pyruvate dehydrogenase deficiency?

  Neurodegeneration and muscle spasticity

  
• How does arsenic poisoning affect the PDH complex?

  Inhibits E2 by affecting lipoic acid
• What is the result of arsenic poisoning on pyruvate levels?

  Accumulation of pyruvate and lactate
• What catalyzes the synthesis of citrate from acetyl CoA and oxaloacetate?

  Citrate synthase

  
• What inhibits aconitase?

  Fluoroacetate

  
• What is the product of the oxidative decarboxylation of isocitrate?

  α-ketoglutarate

  
• What does isocitrate dehydrogenase produce during its reaction?

  1 NADH and 1 CO2
• What activates isocitrate dehydrogenase?

  ADP and Ca2+
• What inhibits α-ketoglutarate dehydrogenase complex?

  NADH and succinyl CoA

  
• What is produced during the cleavage of succinyl CoA?

  Succinate and GTP

  
• What is substrate-level phosphorylation?

  Generation of GTP by succinate thiokinase
• What is the electron acceptor in the oxidation of succinate?

  FAD
• What is the product of the oxidation of malate?

  Oxaloacetate and NADH

  
• What are the most important regulatory enzymes in the TCA cycle?

  Citrate synthase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase

  
• How many NADH and FADH2 are produced in one cycle of TCA?

  3 NADH and 1 FADH2
• How much ATP is produced from the oxidation of one NADH?

  Approximately 3 ATP
• How much ATP is produced from the oxidation of one FADH2?

  Approximately 2 ATP

  
• What is the total ATP yield from one acetyl CoA in the TCA cycle?

  12 ATP