Chapter #20: Electron Transport Chain Flashcards
What are the features of the mitochondria?
- Two membranes: Inner membrane (cristae) Outer membrane
- Two compartments: Matrix (inner) Intermembrane space (outer)
Where are the reaction locations in the mitochondria?
- Glycolysis: Cytoplasm
- Citric Acid cycle: Matrix (most)
Succinate dehydrogenase, which oxidizes succinate to form fumarate and produces FADH2 is embedded in the inner mitochondrial membrane.
The outer membrane is permeable to most small molecules.
The inner membrane is impermeable to nearly all ions and small molecules
What is the oxydo-reduction reaction for the electron transport chain?
reduction potential E
reduction potential is a measure of the tendency of the oxidizing agent to be reduced
a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and thereby be reduced or oxidised respectively.
Describe the redox potential of the electron transport chain
Redox potential can be used to get ΔG for a reaction
So, following along with our free energy nomenclature, we can quickly pick up the reduction potential nomenclature:
ΔG = Free energy change of a reaction
E = Reduction potential
Just like standard free energy, the reduction potentials are determined under standardized conditions of 25 C with all the components at 1 M concentration.
ΔG° = Standard free energy change of a reaction
E° = Standard reduction potential (a.k.a. E0)
And finally, again like free energy, conditions are standardized further for biochemical reactions to pH 7.
ΔG°′ = Standard free energy change of a reaction at pH 7
E°′ = Standard reduction potential at pH 7 (a.k.a. E′0)
Now to get ΔEo’ (proportional to the ΔGo’ for a reaction), you combine two half reactions shown in the table on the next slide…
Describe the Redox Potential: Oxidative Phosphorylation
How do you predict the reaction of a oxidative phosphorylation reaction?
What direction would you expect electrons to flow in the electron transport chain?
Why do we need intermediary steps in the electron transport chain?
What are the four transmembrane protein complexes of the respiratory/electron transport chain?
- NADH-Q oxidoreductase (Complex I)
- Succinate-Q reductase (Complex II)
- Q-cytochrome c oxidoreductase (Complex III)
- Cytochrome c oxidase (Complex IV) II
How does Complex II differ from the other three?
Complexes I, III, and IV pump protons across the inner mitochondrial membrane through use of electron flow, Complex II does not pump protons.
How do electrons flow in Complex I?
What is used to pump protons out of the matrix?
Electrons flow through the complexes, and the free energy change associated with the transfer of electrons is used to pump protons (Complexes I, III, and IV) out of the matrix and into the intermembrane space of the mitochondria.
- Between the three main complexes, the electrons are transported by two special carriers:
- Coenzyme Q (a.k.a. Q, or ubiquinone), a hydrophobic quinone
In which parts of the cell would these electron carriers like to travel based on their hydrophobicity?
What is Coenzyme Q?
Derivative of quinone, with a long hydrophobic tail.
*The length of the tail can vary, but 10 isoprene units is common (coenzyme Q10)
What is the second carrier used to pump protons out of the matrix?
- Electrons flow through the complexes, and the free energy change associated with the transfer of electrons is used to pump protons (Complexes I, III, and IV) out of the matrix and into the intermembrane space of the mitochondria.
- Between the three main complexes, the electrons are transported by two special carriers:
1. Coenzyme Q (a.k.a. Q, or ubiquinone), a hydrophobic quinone
2. Cytochrome c, a small (12 kD) soluble, heme-containing protein
What does electron flow in the complexes do?
- Electron flow within the complexes in the inner-mitochondrial membrane generates a proton gradient.
- These complexes appear to be associated with one another in what is respirasome.
What would a diagram of the first step of the electron transport chain look like?
What would a diagram of the second step of the electron transport chain look like?
What would a diagram of the third step of the electron transport chain look like?
What would a diagram of the fourth step of the electron transport chain look like?
What is the difference in pH on the outside of the matrix?
In actuality, the pH outside is about 1.4 units lower than the pH inside.
What are the take home messages for the electron transport chain?
The electron transport chain is present in the mitochondrial intermembrane.
- The reduction potential is a measure of the tendency of the oxidizing agent to be reduced.
- The respiratory chain or electron transport chain consists of four transmembrane protein complexes that catalyze a series of redox reactions.
- The regeneration of redox power is associated with the movement of protons from the matrix to the intermembrane space.
