Question

which statement below best describes the result of pumping hydrogen ions across the inner mitochondrial membrane?
atp is synthesized from adp + ™i.
the ph of the intermembrane space increases.
a proton - motive force is generated.
fad is reduced.

Explanation:

When hydrogen ions (\(H^+\)) are pumped across the inner mitochondrial membrane, a concentration gradient of \(H^+\) is created. This gradient, along with the electrical potential difference (due to the charge of \(H^+\)), forms the proton - motive force.

• For the option “ATP is synthesized from ADP+\(\ce{P_i}\)”: While ATP synthesis (\(ADP +\ce{P_i}\to ATP\)) is related to the proton - motive force (as ATP synthase uses the proton - motive force to drive this reaction), the direct result of pumping \(H^+\) is the generation of the proton - motive force, not the immediate synthesis of ATP.
• For the option “The pH of the intermembrane space increases”: Pumping \(H^+\) into the intermembrane space increases the \(H^+\) concentration there. Since \(pH=-\log[H^+]\), an increase in \([H^+]\) leads to a decrease in pH (not an increase).
• For the option “FAD is reduced”: FAD (flavin adenine dinucleotide) is reduced during the citric acid cycle (e.g., \(FAD + 2H\to FADH_2\)) and is not directly related to the pumping of \(H^+\) across the inner mitochondrial membrane.

Answer:

A proton - motive force is generated.