Glycolysis and TCA cycle

• What is the definition of glycolysis?

  Glycolysis is the sequence of reactions converting glucose (or glycogen) to pyruvate or lactate with production of ATP.
• What does the term "Embden-Meyerhof pathway" refer to?

  It refers to the glycolysis pathway discovered in 1940.
• What are the Greek origins of the word "glycolysis"?

  The word "glycolysis" comes from "glyco" meaning sweet sugar and "lysis" meaning dissolution.
• Why is glycolysis considered a universal pathway?

  Because it occurs in all living cells.
• In which cellular location does glycolysis occur?

  Glycolysis occurs in the cytosol of the cell.
• What are the two conditions under which glycolysis can occur?

  Glycolysis can occur in both anaerobic and aerobic conditions.
• Why is glycolysis essential for the brain?

  Because the brain is dependent on glucose for energy.
• What is the significance of glycolysis in tissues lacking mitochondria?


  It serves as a major pathway for ATP synthesis in those tissues.
• What are the end products of glycolysis?

  The end products of glycolysis are pyruvate or lactate.
• What are the three irreversible steps in glycolysis?

  The three irreversible steps are catalyzed by hexokinase (or glucokinase), phosphofructokinase, and pyruvate kinase.
• What is gluconeogenesis?

  Gluconeogenesis is the synthesis of glucose from pyruvate.
• What is the net production of ATP in aerobic glycolysis?

  The net production of ATP in aerobic glycolysis is 8 ATP.
• What is the net production of ATP in anaerobic glycolysis?

  The net production of ATP in anaerobic glycolysis is 2 ATP.
• How is the rate of glycolysis regulated?

  The rate of glycolysis is regulated by controlling the three irreversible enzymes: hexokinase/glucokinase, phosphofructokinase, and pyruvate kinase.
• What role does insulin play in glycolysis regulation?

  Insulin stimulates the synthesis of all key enzymes of glycolysis.
• What is the effect of glucagon on glycolysis?

  Glucagon inhibits the activity of all key enzymes of glycolysis.
• What is the primary function of the TCA cycle?

  The primary function of the TCA cycle is to provide energy through the complete oxidation of acetyl CoA.
• What percentage of ATP is synthesized in the TCA cycle?

  60-70% of ATP is synthesized in the TCA cycle.
• Who proposed the citric acid cycle and when?

  The citric acid cycle was proposed by Hans Adolf Krebs in 1937.
• Where are the enzymes of the TCA cycle located?

  The enzymes of the TCA cycle are located in the mitochondria.
• What is the first step of the TCA cycle?

  The first step is the condensation of acetyl CoA and oxaloacetate to form citrate, catalyzed by citrate synthase.
• What is produced during the conversion of isocitrate to α-ketoglutarate?

  NADH is produced along with the liberation of CO2 during this conversion.
• What is substrate-level phosphorylation in the TCA cycle?

  Substrate-level phosphorylation occurs when succinyl CoA is converted to succinate, coupled with the phosphorylation of GDP to GTP.
• How many ATP are produced from one Acetyl CoA in the TCA cycle?

  A total of 12 ATP are produced from one Acetyl CoA in the TCA cycle.
• What is the amphibolic nature of the citric acid cycle?

  The citric acid cycle is amphibolic because it has both catabolic (breakdown) and anabolic (formation) functions.
• What are the catabolic functions of the TCA cycle?

  The TCA cycle is the final common pathway for the oxidation of carbohydrates, fats, and proteins (amino acids).
• What are the anabolic functions of the TCA cycle?

  The anabolic functions include the formation of amino acids, glucose, fatty acids, and cholesterol from acetyl CoA.
• What is the summary of the TCA cycle?

  • The TCA cycle is the final pathway for the oxidation of carbohydrates, lipids, and proteins.
  • Acetyl CoA reacts with oxaloacetate to form citrate.
  • Citrate is degraded through a series of dehydrogenations and decarboxylations.
  • Reduces coenzymes, releases 2 CO2, and regenerates oxaloacetate.
  • Major pathway for ATP formation located in the mitochondria.
  • Important for gluconeogenesis, fatty acid synthesis, and amino acid interconversion.