The balance between the oxidized and reduced forms of nicotinamide adenine dinucleotide is called the NAD/NADH ratio. This ratio is an important component of what is called the "redox state" of a cell, a measurement that reflects both the metabolic activities and the health of cells. The effects of the NAD/NADH ratio are complex, controlling the activity of several key enzymes, including glyceraldehyde 3-phosphate dehydrogenase and pyruvate dehydrogenase. In healthy mammalian tissues, estimates of the ratio between free NAD and NADH in the cytoplasm typically lie around 700:1; the ratio is thus favourable for oxidative reactions. The ratio of total NAD/NADH is much lower, with estimates ranging from 3–10 in mammals. In contrast, the NADP/NADPH ratio is normally about 0.005, so NADPH is the dominant form of this coenzyme. These different ratios are key to the different metabolic roles of NADH and NADPH.