Metabolism and Energy Production

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CHAPTER 23

• Metabolism and Energy Production

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What happens after glycolysis?

• When oxygen is present (under aerobic
  conditions)
• The acetyl-CoA is sent into the citric acid
  cycle, which is followed by the electron
  transport chain.
• The latter process makes most of the ATP.

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A. The Citric Acid Cycle

• Overall, a series of reactions that degrade
  acetyl-CoA to CO2 and energy
• This energy is used to produce NADH and FADH2
• NADH and FADH2 are the electron limousines that
  shuttle the electrons to the electron transport
  chain, where they are used to generate a lot of
  ATP.

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Summary of Products Citric Acid Cycle

• You get
• 2 CO2
• 3 NADH
• 1 FADH2
• 1 GTP which is used to form ATP
• These are the products from ONE acetyl-CoA.
  Double those numbers if you are considering the
  products from one glucose molecule through the
  whole process.

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Citric Acid Cycle Regulation

• Function of citric acid cycle generate ATP
• So, when the cell needs energy, pyruvate is
  converted to acetyl-CoA, and the citric acid
  cycle proceeds.
• But when the cell has sufficient energy, there is
  not much conversion to acetyl-CoA, and the citric
  acid cycle slows.

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B. Electron Carriers

• What have we obtained so far in terms of
  energy-carrying molecules?
• From One Glucose ATP Coenzymes
• Glycolysis 2 2 NADH
• 2 pyruvate --gt
• 2 acetyl-CoA 2 NADH
• Citric acid cycle 2 6 NADH
• 2 FADH2

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How Do The Electron Carriers Work?

• After glycolysis and the citric acid cycle, these
  carriers are in the reduced form.
• As they are oxidized later on, they provide
  energy for the synthesis of ATP.
• In the electron transport chain (which follows
  the citric acid cycle), electrons are passed from
  one intermembrane protein to the next until they
  combine with oxygen to form H2O.
• http//www.science.smith.edu/departments/Biology/B
  io231/etc.html

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C. Oxidative Phosphorylation and ATP

• Oxidative phosphorylation the production of ATP
  from ADP and Pi using the energy released during
  the electron transport chain
• Chemiosmotic model links this energy to a proton
  gradient.
• As electrons are passed along the chain, H is
  passed into the intermembrane space.
• A proton gradient is created, whereby the
  intermembrane space has both a positive charge
  and a lower pH.
• The energy generated by this gradient is used by
  ATP synthase to drive the synthesis of ATP.

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Creation of Proton Gradient

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D. ATP Energy from Glucose

• How much ATP do you get from all of these
  processes?
• ATP from glycolysis
• 2 NADH (which, long-term, give you 4 ATP) 2 ATP
  6 ATP
• Conversion of pyruvate --gt acetyl-CoA
• 2 NADH (one per pyruvate) 6 ATP
• Citric acid cycle
• From each acetyl-CoA 3 NADH, one FADH2, one ATP
• which will, total, give 24 ATP
• The combination of it all 36 ATP per glucose.

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Oxidation of Glucose

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What Happens To All This Glucose?

• If there is extra glucose around -- in excess of
  what our cells need for energy -- what happens to
  it?
• If glucose levels in the brain or blood get low,
  what does the body do?
• Glucose can also be synthesized from
  non-carbohydrate sources as needed.