Cellular Respiration

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Cellular Respiration

• Process by which cells extract energy from food
• Literally its about using bond energy
  (electrons) to regenerate ATP
• May be anaerobic or aerobic

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C6H12O6 6O2 ? 6CO2 6H2O
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Aerobic Respiration as a 3-Act Play

• Act I Glycolysis
• Act II The Krebs Cycle
• Act III Oxidative Phosphorylation and the
  Electron Transport Chain

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Glycolysis

• 6C glucose split
• to 2, 3C pyruvates
• Yield 2 ATP
• Yield 2 NADH
• 10 reaction steps,
• each catalyzed by
• specific enzymes.

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Whats the point of glycolysis?

• The key point of glycolysis is that all cells,
  without even using oxygen, are able to make food
  monomers reactive enough to split down to
  pyruvate. The pyruvate molecules then proceed to
  further steps that extract much more energy from
  the bonds.

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The fate of pyruvate

• In anaerobic conditions, it is converted to
  lactic acid or ethanol, with a yield of 4
  ATP/glucose

• In aerobic conditions, it enters the
  mitochondria, proceeds through Krebs Cycle and
  Oxidative Phosphorylation at the ETC for yield of
  36 ATP/glucose

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Aerobic Respiration as a 3-Act Play

• Act I Glycolysis
• Act II The Krebs Cycle
• Act III Oxidative Phosphorylation and the
  Electron Transport Chain

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Krebs Cycle (aka Citric Acid Cycle)

• A metabolic furnace
• that oxidizes pyruvate
• fuel.
• Each pyruvate is broken
• down to 3 CO2.
• 2 pyruvates ? 2 ATP
• 6 NADH
• 2 FADH2

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Whats the point of Krebs Cycle?

• The point of the Krebs cycle is to reduce
  coenzymes.
• In Krebs, NAD and FAD are reduced to NADH
  FADH2 from the oxidation of pyruvate (or
  actually, Acetyl, CoA).
• The reduced coenzymes, NADH FADH2 act as
  electron taxi cabs, shuttling their key
  passengers to the cristae.

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Mitochondria Anatomy Review

• Remember
• Glycolysis -- in cytosol
• Krebs -- in mito matrix
• Ox Phos at mito cristae
• (in the electron transport chain ETC)

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Aerobic Respiration as a 3-Act Play

• Act I Glycolysis
• Act II The Krebs Cycle
• Act III Oxidative Phosphorylation and the
  Electron Transport Chain
• Chemiosmosis simulation

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Oxidative Phosphorylation and the Electron
Transport Chain
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Whats the point of oxidative phosphorylation at
the ETC?

• The electrons, originally from glucose, are
  delivered to the ETC by NADH and FADH2, and are
  passed down the ETC.
• This electrical energy runs a molecular
  machinery that pumps protons across the cristae.
• These protons pass back through the cristae at
  the ATP synthase enzyme, regenerating ATP!

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Review of Cells Metabolism

• Enzymes Activation Energy
• ATP and coupled reactions
• Cellular Respiration
• Glycolysis
• Anaerobic fermentation or lactic acid formation
• Aerobic, proceed to below
• Krebs Cycle
• Ox. Phos. the ETC