Electron Transport and Oxidative Phosphorylation
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A comprehensive set of question-and-answer flashcards covering mitochondrial structure, electron transport complexes, proton pumping, ATP yields, and the glycerol-phosphate and malate-aspartate shuttles, designed to help students review Electron Transport and Oxidative Phosphorylation.
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Which mitochondrial membrane is relatively permeable to small molecules and ions?
The outer mitochondrial membrane.
The inner mitochondrial membrane is impermeable to which two key electron carriers?
NADH and FADH2.
Where in the cell do glycolysis, the Krebs cycle, and β-oxidation occur, respectively?
Glycolysis in the cytosol; Krebs cycle and β-oxidation in the mitochondrial matrix.
How many NADH molecules are produced per glucose during glycolysis?
Two NADH per glucose.
How many NADH are generated by the pyruvate dehydrogenase reaction per glucose?
Two NADH per glucose.
What are the total reducing equivalents produced by the Krebs cycle per glucose?
Six NADH and two FADH2.
On which side of the inner mitochondrial membrane do NADH and FADH2 bind to the ETC complexes?
The matrix side.
What is the final electron acceptor in the electron transport chain?
Molecular oxygen (O2), which is reduced to water (H2O).
Name the four major protein complexes of the electron transport chain in order.
Complex I, Complex II, Complex III, Complex IV.
Which complex contains NADH dehydrogenase activity and pumps 4 protons per NADH oxidized?
Complex I.
List the electron transfer sequence within Complex I.
NADH → FMN → Fe-S centers → ubiquinone (CoQ).
What enzyme is embedded in Complex II and what cofactor does it use?
Succinate dehydrogenase using FAD/FADH2.
Does Complex II pump protons across the membrane?
No, Complex II does not pump protons.
How many protons are pumped by Complex III per pair of electrons?
Four protons.
Which mobile electron carrier transfers electrons from Complex III to Complex IV?
Cytochrome c.
Complex IV is also known by what enzyme name?
Cytochrome c oxidase.
How many protons does Complex IV pump for each pair of electrons delivered?
Two protons.
Total protons translocated per NADH oxidized through the ETC equal what number?
10 H⁺ per NADH.
Total protons translocated per FADH2 oxidized equal what number?
6 H⁺ per FADH2.
According to the chemiosmotic theory, how many protons are required to synthesize one ATP?
Approximately 4 H⁺ per ATP (including transport costs).
How many ATP are generated per mitochondrial NADH?
About 2.5 ATP.
How many ATP are generated per mitochondrial FADH2?
About 1.5 ATP.
Per glucose, how many ATP are produced inside the matrix from pyruvate dehydrogenase and two turns of the Krebs cycle?
25 ATP (12.5 ATP per pyruvate × 2).
Which shuttle operates in muscle and brain to transfer cytosolic NADH electrons into the mitochondria, and what carrier is generated?
The glycerol phosphate shuttle; it converts cytosolic NADH into mitochondrial FADH2.
Total ATP yield per glucose in tissues using the glycerol phosphate shuttle equals what value?
30 ATP per glucose.
Which shuttle functions in liver and heart to move cytosolic NADH into the matrix without changing its identity?
The malate–aspartate shuttle.
Total ATP yield per glucose in tissues using the malate–aspartate shuttle equals what value?
32 ATP per glucose.
Why can’t cytosolic NADH from glycolysis directly enter the mitochondrial matrix?
Because the inner mitochondrial membrane is impermeable to NADH, requiring shuttles for electron transfer.