QuestionSBA
QuestionChoice
The electron transport chain drives protons out of the mitochondrial matrix across the inner mitochondrial membrane to create an electrochemical gradient into the matrix through the F0 component of ATP synthase.
10001082
b
The electron transport chain drives protons into the mitochondrial matrix
QuestionChoice
FADH2 is converted to FAD by complex 2 (succinate dehydrogenase, also involved in the citric acid cycle). Complex 2 does not pump protons itself but transfers electrons to ubiquinone, which are subsequently accepted by complex 3 (which pumps 4 protons). These electrons are then transferred to cytochrome C which transfers the electrons to complex 4 which pumps 2 protons (total protons pumped = 6). The electrons are finally transferred to oxygen, the terminal acceptor, which generates water.
10001084
d
FADH2 is converted to FAD by complex 1, resulting in the pumping of 10 protons across the inner mitochondrial membrane
QuestionChoice
ATP synthase is formed of the F0 proton pore and the F1 rotating component which binds and combines ADP and phosphate molecules. This occurs in 3 stages: binding, combination and release. A full turn of F1 requires 3 individual 120-degree rotations of F1 (each of which produces 1 ATP molecule). All 3 stages (binding, combination and release) occur simultaneously, meaning they occur 3 times during each 360-degree rotation, generating 3 ATP molecules.

8 protons have to pass through the F0 pore to facilitate a full rotation of F1. Since the ATP synthesis reaction occurs in one out of the three stages of ATP synthase rotation (combination stage), we can deduce that only 1/3 of the energy from the movement of the 8 protons is used to drive the ATP synthesis reaction, whilst the rest is used to bind the ADP and phosphate (binding stage) and release the newly formed ATP (release stage).

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10001085
e
The ATP synthesis reaction demands most of the energy that the proton gradient confers onto ATP synthase
QuestionChoice
The greatest changes in redox potential in the electron transport chain are from NADH to iron-sulfur complexes, from cytochrome b562 to cytochrome b566, and from cytochrome a to cytochrome a3, all of which occur in complexes 1, 3 and 4. This corresponds with the complexes in which protons are pumped across the inner mitochondrial membrane as there is sufficient energy to drive this movement.
10001081
a
The reactions with the largest changes in redox potential in the electron transport chain occur within complexes 1, 3 and 4
QuestionChoice
2,4-dinitrophenol is a molecule which uncouples the electron transport chain from ATP synthase by inserting itself into the inner mitochondrial membrane and facilitating proton transport back into the matrix. This dissipates the electrochemical gradient and leads to an increased rate of oxidative phosphorylation without ATP generation.
10001083
c
2,4-dinitrophenol increases the rate of oxidative phosphorylation, boosting ATP production
Concept
Chapter
2693
3880
Electron transport chain
Topic
180
Biochemistry
12763
Regarding oxidative phosphorylation, which of the following statements is true?
a