Question

which statement best explains why more atp is made per molecule of nadh than per molecule of fadh₂? fewer protons are pumped across the inner mitochondrial membrane when fadh₂ is the electron donor than when nadh is the electron donor. there is more nadh than fadh₂ made for every glucose that enters cellular respiration. it takes more energy to make atp from adp and p; using fadh₂ than using nadh. fadh₂ is made only in the citric acid cycle while nadh is made in glycolysis, acetyl coa formation, and the citric acid cycle. the h⁺ gradient made from electron transport using nadh is located in a different part of the mitochondrion than the h⁺ gradient made using fadh₂.

Explanation:

During oxidative phosphorylation, electrons from NADH and FADH₂ enter the electron - transport chain. NADH donates electrons at a higher energy level (Complex I), while FADH₂ donates electrons at a lower energy level (Complex II). When electrons are donated by NADH, more protons are pumped across the inner mitochondrial membrane. The number of protons pumped is directly related to the amount of ATP synthesized (since ATP synthase uses the proton gradient). Fewer protons are pumped when FADH₂ is the electron donor, resulting in less ATP per molecule of FADH₂ compared to NADH.

The second option about the quantity of NADH and FADH₂ per glucose is not relevant to the per - molecule ATP production difference. The third option is incorrect as the energy to make ATP from ADP and \(P_i\) via ATP synthase is derived from the proton gradient, not directly from FADH₂ or NADH. The fourth option about where they are made does not explain the per - molecule ATP difference. The fifth option about the location of the \(H^+\) gradient is also not the reason for the per - molecule ATP difference.

Answer:

Fewer protons are pumped across the inner mitochondrial membrane when \(FADH_2\) is the electron donor than when \(NADH\) is the electron donor.