Pyruvate Oxidation

• What are the two possibilities for what happens after glycolysis?

  1. Oxygen is present

  The hydrogen acceptors (NADH, and FADH2) enter the mitochondria for the Krebs Cycle. 'Aerobic Respiration'

  
  

  2. Insufficient oxygen

  The pyruvate stays in the cytoplasm where it is converted to lactic acid or ethanol in anaerobic respiration
• Other name for pyruvate oxidation?

  Link reaction
• 3 Possible Pyruvate Pathways

  1. Ethanol Fermentation

  2. Lactic Acid Fermentation

  3. Pyruvate Oxidation
• What type of cells undergo ethanol fermentation?

  bacteria or yeast cells

  
• Ethanol fermentation equation, where the products are from

  pyruvate + NADH + H+ => ethanol + CO2 + NAD+

  - products from glycolysis
• When does ethanol fermentation occur?

  This occurs when there is NOT ENOUGH Oxygen to go through the "Link Reaction"
• What cells does lactic acid fermentation occur in?

  Animal cells - temporary absence of oxygen

  
• Lactic acid fermentation equation and where the products are from

  pyruvate + NADH + H+ => lactic acid + NAD+

  -products from glycolysis
• When does lactic acid fermentation occur?

  This occurs when there is NOT ENOUGH Oxygen to go through the "Link Reaction"
• Lactic acid and ethanol fermentation production of ATP and NAD

  Both fermentation steps above do NOT directly create any high energy (ATP) compounds but they do both release NAD+ to allow the cell to continue glycolysis
• What is a Coenzyme-A (CoA)?

  What is it?: A carrier that helps enzymes hold and modify molecules (derivative of Vitamin B)

  
• What do coenzyme-A's contain?

  It contains a sulphur and hydrogen functional group (-SH)
• What are the two codes used in relation to coenzyme-A?

  1. CoASH (unbonded coenzyme-A)

  2. -CoA (attached to another molecule)
• Where does pyruvate oxidation occur in?

  In mitochondria - oxygen present

  
• Pyruvate oxidation equation


  pyruvate + NAD+ + CoA-SH => acetyl-CoA + NADH + H+ + CO2
• Reaction of pyruvate oxidation

  1. 2 Pyruvates (from glycolysis) enters the mitochondrial matrix

  2. Carbon removed from pyruvate (decarboxylation) and acetyl is made

  3. 2 x CO2 molecules diffuse out of the mitochondria, through the cell membrane and into the blood

  4. Coenzyme A (CoA) joins with acetyl to create acetlyCoA

  5. Products: 2 acetyl CoA, 2 NADH
• Decarboxylation and when it occurs in pyruvate oxidation


  - Removal of carboxyl group

  - Carboxyl removed from pyruvate

  - (CO2 released - waste)
• Redox reactions in pyruvate oxidation

  Pyruvate is oxidized - Loses e- + H+ to NAD+* NAD+ becomes reduced NADH (gains e- + H+)
• What does coenzyme-A attach to?

  Attaches to acetyl to form acetyl CoA
• What are the three reactants of pyruvate oxidation?

  2 pyruvate

  2 NAD+

  2 CoA
• What are the four products of pyruvate oxidation?

  2 acetyl-CoA

  2 NADH

  2 CO2

  2 H+