Suppose an individual lacked an enzyme necessary for proper functioning of Compl
ID: 88098 • Letter: S
Question
Suppose an individual lacked an enzyme necessary for proper functioning of Complex II and, as a result, significant energy was lost during electron transfer to this portion of the electron transport chain. Which of the following describes the mostly likely pattern of ATP production from mitochondrial electron carriers in this individual? A. Mitochondrial NADH generates 1 ATP per molecule, while mitochondrial FADH2 generates 1.5 ATP per molecule. B. Mitochondrial NADH generates 2.5 ATP per molecule, while mitochondrial FADH2 generates 0.5 ATP per molecule. C. Mitochondrial NADH generates 1 ATP per molecule, while mitochondrial FADH2 generates 0.5 ATP per molecule. D. Mitochondrial NADH generates 2.5 ATP per molecule while mitochondrial FADH2 generates 1.5 ATP per molecule.
Explanation / Answer
ANSWER B-Mitochondrial NADH generates 2.5 ATP per molecule, while mitochondrial FADH2 generates 0.5 ATP per molecule
1. Complex I also known as the NADH-coenzyme Q reductase or .
2. Complex II also known as succinate-coenzyme Q reductase or succinate dehydrogenase.
3. Complex III also known as coenzyme Q reductase.
4. Complex IV also known as cytochrome c reductase.
normally one NADH yields 2.5 ATP and one FADH gives 1.5 ATP.
In the first step of this complex, succinate is bound and a hydride is transferred to FAD to generate FADH2 and fumarate. FADH2 then transfers its electrons one at a time to the Fe-S centers. Thus once again FAD functions as 2 electron acceptor and a 1 electron donor. The final step of this complex is the transfer of 2 electrons one at a time to coenzyme Q to produce CoQH2.
The overall reaction for this complex is:
complex 2 Succinate + CoQ> Fumarate + CoQH2 Eo ’ = 0.060 V – (+0.031V) = 0.029 V Go ’ = nFEo ’ = 5.6 kJ/mol
complex I NADH + H+ + CoQ > NAD+ + CoQH2 Eo ’ = 0.060 V – (0.315V) = 0.375 V Go ’ = nFEo ’ = 72.4 kJ/mol
For complex II the standard free energy change of the overall reaction is too small to drive the transport of protons across the inner mitochondrial membrane. This accounts for the 1.5 ATP’s generated per FADH2 compared with the 2.5 ATP’s generated per NADH
if individual lacked an enzyme necessary for proper functioning of Complex II and, as a result, significant energy was lost during electron transfer to this portion of the electron transport chain , then 0.5 ATP’s generated per FADH2 ( succinate-coenzyme Q reductase or succinate dehydrogenase )compared , with the 2.5 ATP’s generated per NADH(complex 1)