Pages 91102, 767781

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Lecture 39 Pages 91-102, 767-781 Mitochondria
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Glucose
Glycolysis oxidizes glucose to pyruvate in the
cytoplasm yielding 2 molecules of ATP and 2
molecules of NADH. Further oxidation of the
pyruvate occurs in the mitochondria matrix.
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Approximately 1 micron in size
The outer membrane contains large aqueous
channels consisting of porin that allow molecules
less than 5000 daltons to enter passively.
Pyruvate diffuses through porin in the outer
membrane and is transported across the inner
membrane by a pyruvate - proton symporter.
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Pyruvate enters the matrix and is converted to
acetyl CoA by pyruvate dehydrogenase.
Note that carbon is being oxidized and NAD is
being reduced. A molecule of CO2 is produced.
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Simple view of citric acid cycle.
Input 1 acetyl CoA 3 NAD 1 FAD 1 GDP 1
Pi Output 1 CoA 2 CO2 3 NADH 1 FADH2 1 GTP
FADH2 is another energy carrier that I also
categorize as reducing power.
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• Summary of citric acid cycle
• Completes the oxidation of carbons to CO2.
• Generates high energy electrons (reducing power)
  in the form of NADH and FADH2
• Small amount of ATP produced by the exchange
  reaction of GTP ADP gt GDP ATP.
• Intermediates from the citric acid cycle can be
  used to synthesize other molecules such as amino
  acids.

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Glucose
ATP NADH
Glycolysis (cytosol)
Pyruvate
CO2 NADH
Acetyl CoA
CO2 NADH and FADH2 GTP
Citric Acid Cycle (Mitochondria)
You are responsible for knowing the structures of
the underlined compounds.
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Oxidative phosphorylation converts the reducing
power of NADH and FADH2 from the citric acid
cycle to chemical energy in ATP.
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• Through a series of electron transfer steps, high
  energy electrons in NADH and FADH2 are
  transferred to O2 to form the stable product H2O.
  Most of the oxygen you breath in is utilized for
  this reaction.
• The energetically favorable reaction of
  transferring electrons to O2 is coupled to the
  energetically unfavorable reaction of creating an
  electrochemical proton gradient.
• The subsequent transport of protons down the
  electrochemical proton gradient powers the
  synthesis of ATP.

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How the proton gradient drives ATP synthesis?
The proton gradient generated by the electron
transport chain has a voltage gradient (membrane
potential) and a chemical gradient. The movement
of 1 mole of protons from the intermembrane space
to the matrix space has a ?G -4.6 kcal/mole, an
energetically favorable process. Sometimes this
is called the proton motive force.
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The movement of protons through ATP synthase is
coupled to synthesis of ATP. The movement of the
protons causes part of the ATP synthase to
rotate. The mechanical energy from this rotation
is converted to the chemical energy of ATP.
12 kcal of energy are required to synthesize 1
mole of ATP at the high concentrations found in
the cell. Movement of 1 mole of protons yields
4.6 kcal of energy. Hence 3 protons must move
across the membrane to produce a molecule of ATP
under biological conditions (not standard
conditions).
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Amazing evidence for rotation.
Fluorescent
Ni chelated surface binds his-tag
Addition of ATP causes actin filament to spin.
The ATP synthase is functioning in reverse from
what it normally does when it makes ATP.
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