NADH vs. NADPH: Where is each one used and why that instead of the other?

Question

I know NADH is used in cellular respiration and NADPH is used in photosynthesis. What difference does the phosphate group make that the same one isn't or can't be used for both? Is there a greater reason for this separation or is it just coincidental? Why can't the two be interchanged?

Answer 1

NADH and NADPH are very different molecules and are used for different reactions in the cellular environment. NADH is an electron carrier and the reduced form of NAD+, which is formed at various points of the glucose metabolism pathway and other catabolic processes. NADH exchanges its electrons in the mitochondria at the electron transport chain, where these electrons are used to pump protons up their concentration gradient (from mitochondrial membrane to inner mitochondrial space). The protons are then moved through the canal of ATP synthase, down the concentration gradient, generating ATP.

NADPH is a molecule formed from the Pentose Phosphate pathway, a separate pathway where glucose-6 Phosphate enters. NADPH plays a role in fatty acid synthesis and antioxidant formation. Concerning antioxidant formation, NADPH works with the enzyme glutathione reductase, which keeps Glutathione (one of the bodies antioxidants) levels high and constantly being recycled. Glutathione protects the cells against free radicals, which can damage the cell.