The Krebs Cycle

• Where does the Krebs cycle take place?


  In the mitochondrial matrix.
• What does the Krebs cycle produce for every molecule of acetyl coenzyme A?


  Two molecules of CO2, one molecule of ATP, 3 reduced NAD and 1 reduced FAD.
• What happens to acetyl CoA after the link reaction?

  It merges with a 4 carbon molecule called oxaloacetate to create a 6 carbon molecule called citrate.
• What happens to the 6 carbon molecule in the Krebs cycle?


  It is decarboxylated and dehydrogenated, forming a 5 carbon molecules and releasing a molecules of CO2 and hydrogen.
• What happens to the hydrogen released from the 6 carbon molecule?

  It is used to reduce NAD.
• What happens to the 5 carbon molecule after it is decarboxylated and dehydrogenated?

  It is decarboxylated and dehydrogenated again, forming a 4 carbon molecule whilst releasing a CO2 molecule and 3 hydrogen atoms.
• What happens to the 3 hydrogen molecules released from the 5 carbon molecule?

  2 are used to reduce 2 NAD molecules and 1 is used to reduce 1 FAD molecule.
• What also happens when the 5 carbon molecule is being decarboxylated and dehydrogenated?

  ATP is synthesised by substrate-level phosphorylation.
• How is the Krebs cycle a cycle?

  The 4 carbon molecule gets regenerated by decarboxylation for the next turn of the cycle.
• What do the reduced coenzymes NADH and FADH do with their gained electrons and protons?

  Donate them to the electron transport chain in oxidative phosphorylation for ATP synthesis.
• What molecule only participates in the Krebs cycle?

  FAD.