What is the function of the electron carriers NAD+ and FAD?
Both FAD and NAD function as electron carriers. When an electron pair is transferred to these molecules, either one or two hydrogens are also transferred. FAD has accommodation for two hydrogens while NAD can accept one hydrogen. In NAD, then, an electron pair and one hydrogen are transferred, with a second hydrogen released into the medium. This subtle chemical difference is why the reduced form of FAD is written FADH2 while the reduced form of NAD is written NADH + H+. These compounds are particularly appropriate electron carriers because they readily accept an electron pair and they also readily donate an electron pair. We saw FAD act in the Kreb’s cycle, shown in the figure. FAD accepts an electron pair from succinate, becoming FADH2. FADH2 carries the electron pair to the electron transport chain, where it releases its electrons at such position in the chain that two ATPs are subsequently formed. The figure also shows that NAD operates as an electron carrier at three places in the
