Question

which molecule can shuttle the greatest number of hydrogen ions? glucose water nad+ fad+

Explanation:

NAD+ (nicotinamide adenine dinucleotide) can accept two hydrogen ions (\(H^+\)) and two electrons (\(e^-\)) to form NADH (\(NAD^+ + 2H^+ + 2e^- \to NADH + H^+\)). FAD+ (flavin adenine dinucleotide) can accept two hydrogen ions and two electrons to form FADH₂ (\(FAD^+ + 2H^+ + 2e^- \to FADH_2\)). Glucose (\(C_6H_{12}O_6\)) is a sugar molecule and does not shuttle hydrogen ions in the context of electron - transport - chain - related hydrogen - ion shuttling. Water (\(H_2O\)) can dissociate into \(H^+\) and \(OH^-\) (\(H_2O
ightleftharpoons H^+ + OH^-\)), but its role is not in shuttling hydrogen ions in the way that electron - carrier molecules do. Among the given options, NAD+ is a major electron (and hydrogen - ion - related) carrier in cellular respiration. When it is reduced, it takes up hydrogen ions. In the electron - transport chain, for each NADH that donates electrons, more protons (\(H^+\)) are pumped across the mitochondrial membrane compared to FADH₂.

Answer:

NAD+