BCEM 393 Lecture Notes - Lecture 13: Standard Hydrogen Electrode, Oxidative Phosphorylation, Faraday Constant
16 Jun 2018
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Oxidation Phosphorylation
LOCALIZATION OF OXIDATIVE PHOSPHORYLATION
- The citric acid cycle occurs in the mitochondrial matrix
- Oxidative phosphorylation occurs in the inner mitochondrial membrane, which is impermeable
to all ions and polar molecules
- The inner mitochondrial matrix is highly folded, which increases the surface area, and
therefore increases the amount of oxidative phosphorylation the occurs
ENERGY FOR THE BODY
- Sedentary male (70kg, ~155 lbs)
- Requires 8400 kJ (2000 kcal)/day ~83 kg of ATP
- At any given time, we possess ~250 g ATP
- ATP is recycled from ADP primarily through oxidative phosphorylation
- ATP is formed as a result of the transfer of electrons from NADH or FADH2 to O2 by a series
of electron carriers
HOW MUCH ENERGY IS RELEASED BY THE REDUCTION OF O2 WITH ELECTRON CARRIER
NADH?
- Consider reduction potentials:
- For an two half-cells, electrons flow to the half-cell with the more positive reduction
potential (E)
- The strength of that tendency is proportional to the difference in reduction potentials, ∆E
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- The energy made available by this spontaneous electron flow is: ∆G = -nF∆E or ∆G° = -
nF∆E°
- n is the number of
electrons transferred
- F is Faraday constant
(96.48 kJ mol-1 V-1)
- Relative to the standard
hydrogen electrode
- A negative reduction
potential means that the
oxidized form of a
substance has lower
affinity for electrons
than does H2
ELECTRON FLOW FROM NADH
TO O2 — ELECTRON-
TRANSPORT CHAIN
- Electrons flow through a
series of 4 electron carriers
(complexes)
- Complex 1: NADH-Q
oxidoreductase
- Complex 2: Succinate-Q
reductase
- Complex 3: Q-cytochrome
c oxidoreductase
- Complex 4: Cytochrome c oxidase
- Electron carriers are coupled through sequential redox reactions
- The members of the electron-transport chain are arranged so that the electrons flow towards
components with more positive reduction potentials (a higher electron affinity)
- Molecules with higher reduction potentials are more likely to get reduced
ELECTRON CARRIERS — NADH VS FADH2
- NADH and FADH2 enter the electron carrier chains at different points of entry
- For NADH:
- Electrons are transferred through NADH-Q oxidoreductase (1), Q-cytochrome c
oxidoreductase (3), and cytochrome c oxidase (4)
- For FADH2:
- Succinate-Q reductase, contains the succinate dehydrogenase that generates FADH2 in
the citric acid cycle (located in the inner membrane)
- Electrons from this FADH2 enter the electron-transport chain at Q-cytochrome c
oxidoreductase (3)
WHY DOES FADH2 ENTER DOWNSTREAM OF NADH?
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Document Summary
The citric acid cycle occurs in the mitochondrial matrix. Oxidative phosphorylation occurs in the inner mitochondrial membrane, which is impermeable to all ions and polar molecules. The inner mitochondrial matrix is highly folded, which increases the surface area, and therefore increases the amount of oxidative phosphorylation the occurs. Requires 8400 kj (2000 kcal)/day ~83 kg of atp. At any given time, we possess ~250 g atp. Atp is recycled from adp primarily through oxidative phosphorylation. Atp is formed as a result of the transfer of electrons from nadh or fadh2 to o2 by a series of electron carriers. How much energy is released by the reduction of o2 with electron carrier. For an two half-cells, electrons flow to the half-cell with the more positive reduction potential (e) The strength of that tendency is proportional to the difference in reduction potentials, e.
