Oxidative Phosphorylation

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Oxidative Phosphorylation

• The Bodys Game of Hot Potato

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AKA

• Electron Transport System

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Location, Location, Location

• Location
• Inner mitochondrial membrane

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The Meaning of It All

• Purpose
• How Many?

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Break It Down!

• The ETS is a series of oxidation-reduction
  reactions.
• These reactions are facilitated by five enzymes.
• At the end of the ETS, O2 receives electrons (H)
  and ATP is made.

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Supply and Demand

• Where do the electrons come from?
• NADH/FADH2
• These reduced compounds carry the electrons from
  the TCA to the ETS.

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The Final Frontier

• The ETS is the final place for the breakdown of
  macronutrients to make ATP.
• TCA ? ETS ? ATP

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Things to Remember

• Reduced Compounds
• Chemicals that have gained an electron.
• Electrons are represented by H in biochemistry.
• NADH FADH2
• Oxidized Compounds
• Chemicals that have lost an electron.
• NAD FAD

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Things to Remember

• Reducing Agent
• The Electron/H donor.
• Oxidizing Agent
• The Electron/H acceptor.
• Redox Pair
• The conjugate forms of a molecule in reduced and
  oxidized forms.
• NAD ? NADH

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The System

• Five Enzyme Complex
• The enzymes are called complexes.
• I through IV pass electrons to each other.
• V catalyzes the production of ATP, and is called
  ATP Synthase.

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Enzymes and Complexes

• NADH Dehydrogenase
• Transfers the H on NADH to complex I.
• Coenzyme Q
• Carries H from complexes I II to complex III.
• Cytochromes
• Porphyrin ring, containing Fe.
• Carry electrons down the transport system.

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Im Open

• Who do we pass the electron to?
• This is determined by the
• Standard Reduction Potential.

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Standard Reduction What?

• Standard Reduction Potential
• A measure of the tendency of a molecule to lose
  electrons.
• A more negative SRP A greater tendency to lose
  electrons (oxidation).
• A more positive SPR A greater tendency to gain
  electrons (reduction).

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Stop for Directions!

• Which way do the electrons move?
• From more negative SRPs to more positive SRPs.
• Remember, electrons are negative and move away
  from negativity and toward positivity.

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Building ATP

• Complexes I IV
• No ATP made.
• Proton gradient (Potential Energy) created.

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Building ATP

• Complex V (ATP Synthase)
• Uses the Potential Energy from the proton
  gradient to make ATP.

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Get Out the Popcorn
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Smugglers Blues

• NADH is also made outside of the mitochondria,
  but it cannot get to the ETS because the inner
  mitochondrial membrane is impermeable.
• So, the NADH must sneak into the mitochondria via
  the
• Malate Aspartate Shuttle

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Next Stop, The Matrix

• How does the Malate Aspartate Shuttle Work?
• The NADH on the outside gives its H to OAA
  changing it to malate. The malate crosses the
  inner membrane and releases the smuggled H to an
  NAD in the matrix, forming NADH that can be used
  in the ETS.

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The Underground Railroad

• The Glycerophosphate Shuttle
• Works much like the Malate Aspartate Shuttle.
• The NADH on the outside gives its H to DHAP
  changing it to Glycerol 3 - Phosphate. The
  Glycerol 3 - Phosphate crosses the inner
  membrane and releases the smuggled H to an FAD in
  the matrix, forming FADH2 that can be used in the
  ETS.

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Regulation

• Stimulators
• ADP/AMP
• NADH
• FADH2
• O2
• Remember the Big Picture! Reactants stimulate
  pathways.

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Regulation

• Inhibitors
• ATP
• NAD
• FAD
• CO2
• Remember the Big Picture! Products inhibit
  pathways.

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One Last Look