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Electron Transport Chain
Overview
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The electron transport chain (ETC) is a series of protein complexes that
transfer electrons from NADH and FADH₂ to
oxygen.
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Electron transfer is coupled to
proton pumping
across the inner mitochondrial membrane.
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The ETC generates a proton gradient used for ATP synthesis via
ATP synthase.
Electron Carriers
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Coenzyme Q
(ubiquinone) shuttles electrons between Complexes II and III.
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Cytochrome c
transfers electrons between Complexes III and IV.
Inhibitors
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Rotenone
inhibits Complex I.
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Antimycin A
inhibits Complex III.
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Cyanide
inhibits Complex IV.
Dive deeper: Rotenone is a natural pesticide that
inhibits Complex I of the electron transport chain. It is commonly used in
agriculture to control pests, but it can also have toxic effects on
non-target organisms, including humans. Inhibition of Complex I prevents
the transfer of electrons from NADH to
Coenzyme Q, leading to a decrease in
ATP production and an increase in reactive oxygen species (ROS)
generation. Cyanide is a potent inhibitor
of Complex IV and can cause rapid cell death by preventing oxygen
utilization in the electron transport chain.
Uncouplers are compounds that disrupt
the proton gradient, allowing protons to re-enter the mitochondrial matrix
without generating ATP, effectively "short-circuiting" the electron
transport chain.
Practice Questions
What is the primary function of the electron transport chain? Type the letter of the answer: A
A) To transfer electrons from NADH and FADH₂ to oxygen
B) To synthesize ATP from ADP and inorganic phosphate
C) To generate a proton gradient across the inner mitochondrial membrane
D) To produce carbon dioxide and water
Which of the following is a mobile electron carrier in the electron transport chain? Type the letter of the answer: B
A) Coenzyme Q
B) Cytochrome c
C) Complex I
D) Complex IV
What is the role of ATP synthase in the electron transport chain? Type the letter of the answer: B
A) To transfer electrons from NADH to oxygen
B) To synthesize ATP using the proton gradient generated by the electron transport chain
C) To pump protons across the inner mitochondrial membrane
D) To generate reactive oxygen species
Which of the following compounds inhibits Complex I of the electron transport chain? Type the letter of the answer: A
A) Rotenone
B) Antimycin A
C) Cyanide
D) Oligomycin
What is the effect of uncouplers on the electron transport chain? Type the letter of the answer: C
A) They increase ATP production
B) They decrease the proton gradient
C) They allow protons to re-enter the mitochondrial matrix without generating ATP
D) They inhibit electron transfer from NADH to oxygen