Kreb's Cycle aka Citric Acid Cycle

Located in the matrix. 3rd portion of cellular respiration

Step 1 - Condensation

• Acetyl-CoA (2C) enters the cycle and combines with oxaloacetone (4C) to make citrate

• CoA and water are released

Step 2 - Insomerized

• Citrate is isomerized into isocitrate

Step 3 - Dehydrogenase Reaction

• isocitrate is decarboxylated

  • isocitrate > alpha-ketoglutarate

• NAD+ reduced to NADH, producing NADH and H+

Step 4 - Dehyrdrogenase Reaction

• alpha-ketoglutarate is decarboxylated

  • alpha-ketoglutarate > succinyl-CoA

• Coenzyme A is added

• NAD+ reduced to NADH, producing NADH and a H+

Step 5. Substrate-Level Phos[horylation/Synthetase Reaction

• Succinyl-CoA > Succinate

  • CoA is released

• GDP (guanine diphosphate) is phosphorylated by an inorganic phosphate (free-floating phosphate) to become GTP

  • GTP is used as the substrate to phos[horylated ADP > ATP

Step 6. - Dehydrogenase Reaction

• Succinate > fumerate

  • FAD oxidizes succinate

    • turns into FADH2

Step 7. - Hydration reaction

• Fumarate > malate

  • 1 H2O is added

Step 8 - Dehydrogenase Reaction

• Malate > oxaloacetone

  • NAD+ reduced to NADH, producing NADH and a H+

Kreb’s Summary

• 4 CO2 Released/produced

• 2 ATP

• 6 NADH

• 2 FADH2