The reduction potential is a measure of an oxidized molecule's affinity for electrons in a redox half-reaction. The table shows the standard reduction potential of several cytochromes involved in electron transport in the mitochondrial inner membrane.Redox half-reactionE′° (V)Cytochrome a (Fe3+) + e− → Cytochrome a (Fe2+)0.29Cytochrome a3 (Fe3+) + e− → Cytochrome a3 (Fe2+)0.35Cytochrome b (Fe3+) + e− → Cytochrome b (Fe2+)0.08Cytochrome c (Fe3+) + e− → Cytochrome c (Fe2+)0.25Cytochrome c1 (Fe3+) + e− → Cytochrome c1 (Fe2+)0.22According to the information, which series shows the sequence in which electrons pass through the cytochromes during oxidative phosphorylation?A.Cytochrome a → cytochrome a3 → cytochrome b → cytochrome c1 → cytochrome cB.Cytochrome a3 → cytochrome a → cytochrome c → cytochrome c1 → cytochrome bC.Cytochrome a3 → cytochrome a → cytochrome b → cytochrome c1 → cytochrome cD.Cytochrome b → cytochrome c1 → cytochrome c → cytochrome a → cytochrome a3
Question
The reduction potential is a measure of an oxidized molecule's affinity for electrons in a redox half-reaction. The table shows the standard reduction potential of several cytochromes involved in electron transport in the mitochondrial inner membrane.Redox half-reactionE′° (V)Cytochrome a (Fe3+) + e− → Cytochrome a (Fe2+)0.29Cytochrome a3 (Fe3+) + e− → Cytochrome a3 (Fe2+)0.35Cytochrome b (Fe3+) + e− → Cytochrome b (Fe2+)0.08Cytochrome c (Fe3+) + e− → Cytochrome c (Fe2+)0.25Cytochrome c1 (Fe3+) + e− → Cytochrome c1 (Fe2+)0.22According to the information, which series shows the sequence in which electrons pass through the cytochromes during oxidative phosphorylation?A.Cytochrome a → cytochrome a3 → cytochrome b → cytochrome c1 → cytochrome cB.Cytochrome a3 → cytochrome a → cytochrome c → cytochrome c1 → cytochrome bC.Cytochrome a3 → cytochrome a → cytochrome b → cytochrome c1 → cytochrome cD.Cytochrome b → cytochrome c1 → cytochrome c → cytochrome a → cytochrome a3
Solution
In oxidative phosphorylation, electrons move from a molecule with a lower reduction potential to a molecule with a higher reduction potential. This is because a higher reduction potential indicates a greater affinity for electrons.
Looking at the given reduction potentials, the sequence of electron flow would be:
Cytochrome b (0.08 V) → Cytochrome c1 (0.22 V) → Cytochrome c (0.25 V) → Cytochrome a (0.29 V) → Cytochrome a3 (0.35 V)
Therefore, the correct answer is D. Cytochrome b → Cytochrome c1 → Cytochrome c → Cytochrome a → Cytochrome a3.
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