This, the most energy rich of the four currencies, is shown in Figure 12.1a. NADH is a strong reducing agent. It will readily react to allow two hydrogen atoms to be added to molecules, in the general reaction NADH + H+ + X ^ NAD+ + H2X. NAD+ is shown in Figure 12.1b. Addition of hydrogen atoms to molecules, or the removal of oxygen atoms, is called reduction. The opposite of reduction is oxidation, the addition of oxygen. Because oxygen atoms tend to take more than their fair share of electrons in any bonds they make, addition of oxygen means removal of electrons, and vice versa, so the most general definition of reduction is the addition of electrons, with oxidation being defined as the removal of electrons. We will later see NADH acting to reduce complex cell chemicals like pyruvate and acetoacetate. However, when it is acting as an energy currency, NADH simply passes its two hydrogen atoms to oxygen, making water. This releases a lot of energy: Every mole of NADH that is used in this way releases 206 kJ of energy.
Medical NAD+, Pellagra, and Chronic Fatigue Syndrome
Relevance A small fraction of our total body NAD+ is lost from the body each day. New NAD+ 12 1
is synthesized from the vitamin niacin, which in turn can be synthesized from the essential amino acid tryptophan. If we don't get enough niacin or tryptophan, we develop the disease called pellagra. In pellagra parts of our bodies that use a lot of energy, such as the brain, begin to fail. Pellagra killed about 100,000 Americans in the first half of the twentieth century before Joseph Goldberger of the U.S. Public Heath Service showed that it could be prevented and cured by a varied diet. Niacin is now added to all flour, and pellagra is almost unknown in Western countries.
Since chronic fatigue syndrome is manifested as a lack of energy, some people have suggested thatNAD+ itself, given as a dietary supplement, might reenergize the patients. There is no scientific evidence for this idea, but nevertheless many chronic fatigue syndrome sufferers buy and take NAD+ in the hope that it may help.
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