chapter 20: the electron transport chain

negative, donate

a strong reductant has a ____________ potential and will _________ electrons

positive, accept

a strong oxidant has a _____________ potential and will __________ electrons

delta E naught prime (E'°)

standard reduction potential under standard biological conditions (pH 7, 25 C, 1M concentration, and 1 atm pressure); indicates how easily a molecule is reduced

delta E

the actual potential difference in a given reaction, not necessarily under standard conditions

reducing

strong _________ agent = donates electrons

oxidizing

strong _________ agent = readily accepts electrons

positive, negative

If ΔE'° is __________, the reaction is spontaneous (ΔG°' is __________)

negative, positive

If ΔE'° is __________, the reaction is nonspontaneous (ΔG°' is __________)

ubiquinone

what does Q stand for?

ubiquinol

What does QH2 stand for?

NADH-Q oxidoreductase (complex I)

• accepts electrons from NADh, oxidizing it to NAD+, and transfer electrons to Q

• pumps protons (H+) into intermembrane space

• contains FMN and iron-sulfur clusters for electron transfer

Succinate-Q reductase (complex II)

• transfers electrons from FADH2 to Q

• does not pump electrons

• contains FAD and Fe-S clusters for e- transfer

Q-cytochrome c oxidoreductase (complex III)

• transfers electrons from ubiquinone to cytochrome c

• Contains cytochromes b and c₁ and Fe-S clusters

• Pumps protons into the intermembrane space

cytochrome c oxidase (complex IV)

• accepts electrons from cytochrome c and transfers them to O2, reducing it to H2O

• pumps protons into intermembrane space

• contains Cu centers that aid in electron transfer

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equation for NADH-Q oxidoreductase reaction

NADH, FMN, Fe-S, Q, Q2-, QH2

In complex I, electrons flow from _____ to ______ and then through a series of seven _____ clusters to _____, forming _____ —> _______

succinate dehydrogenase

oxidizes succinate into fumarate and generates FADH2, which is used in complex II

FADH2, 2, Fe-S, Q, QH2

In complex II, ______ transfers its ___ e- through a series of _____ clusters, where it is passed to ___ and reduced to ____

2, QH2, cytochrome c, cytochrome b, Q, Q-, 2 H+, intermembrane

in the first half of Q cycle, ___ electrons from ____ are transferred, one to __________ and the other passes through _____________ to reduce ___ into ___. this results in the release of _____ into ______________ space, contributing to the overall proton gradient

QH2, 2, cytochrome c, cytochrome b, Q-, QH2, 2 H+, matrix, 2 H+, intermembrane

in the second half of the Q cycle, a second _____ also gives up ___ e-, one to a second molecule of ___________ and the other passes through ________ to reduce ___ to _____. the second electron transfer results in the uptake of _____ from the _______. there is also an overall release of _____ into ___________ space, contributing to the overall proton gradient

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equation for Q-cytochrome c oxidoreductase reaction

4, heme a, heme a3, Cu_B, heme a3, Cu_B, O2, peroxide, 2 H+, matrix, H+, 2 H2O

In complex IV, ___ reduced cytochrome molecules transfer electrons one by one through: ___ —> _____ —> _______. Reduced centers (______ and ______) bind to ____, leading to the formation of a _______ bridge. The additiion of _____ from the _______ cleaves the bridge. Addition of two more ____ leads to the release of _______.

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write the equation of the cytochrome c oxidase reaction

chemical protons

protons (H⁺) that are involved in the chemical reaction that reduces oxygen (O₂) to water (H₂O).

pumped protons

refer to protons (H⁺) that are actively transported across the inner mitochondrial membrane from the mitochondrial matrix into the intermembrane space.