NADH vs. NADPH — What's the Difference?

Both NADH and NADPH can be likened to charged batteries, loaded with potential energy in the form of electrons. While the primary duty of NADH is to transport electrons for ATP production, NADPH focuses on providing the electrons needed for biosynthetic reactions, defending against oxidative stress, and assisting in the regeneration of reduced glutathione.

NADH, or Nicotinamide Adenine Dinucleotide (reduced form), primarily operates within the mitochondria and is a critical player in the process of cellular respiration. Its primary function is to carry electrons to the electron transport chain, where ATP, the cell's main energy currency, is produced. On the other hand, NADPH, or Nicotinamide Adenine Dinucleotide Phosphate (reduced form), is primarily found in the cytoplasm of the cell. Its chief role lies in photosynthesis in plants and in various anabolic processes within cells.

In plants, the importance of NADPH becomes even clearer. Within the chloroplasts, NADPH is formed during the light reactions of photosynthesis. It then serves to provide the electrons required to convert carbon dioxide into glucose during the Calvin cycle. NADH, while essential in cells of all organisms, does not have the same pivotal role in photosynthesis.

In the realm of energy production, NADH takes center stage. During glycolysis and the citric acid cycle, glucose is broken down, and in the process, NADH molecules are formed. These NADH molecules then donate their electrons to produce ATP. Conversely, NADPH serves as a reducing agent in anabolic reactions, meaning it donates electrons during the synthesis of molecules. This is crucial for processes like lipid synthesis and the neutralization of reactive oxygen species.