A vitamin is an organic compound needed in small quantities that cannot be made in cells. In human nutrition , most vitamins function as coenzymes after modification; for example, all water-soluble vitamins are phosphorylated or are coupled to nucleotides when they are used in cells.  Nicotinamide adenine dinucleotide (NAD + ), a derivative of vitamin B 3 ( niacin ), is an important coenzyme that acts as a hydrogen acceptor. Hundreds of separate types of dehydrogenases remove electrons from their substrates and reduce NAD + into NADH. This reduced form of the coenzyme is then a substrate for any of the reductases in the cell that need to reduce their substrates.  Nicotinamide adenine dinucleotide exists in two related forms in the cell, NADH and NADPH. The NAD + /NADH form is more important in catabolic reactions, while NADP + /NADPH is used in anabolic reactions.
Type 2 diabetes. Type 2 diabetes happens when the body can't respond normally to insulin. Symptoms are similar to those of type 1 diabetes. Many children and teens who develop type 2 diabetes are overweight, and this is thought to play a role in their decreased responsiveness to insulin. Some teens can be treated successfully with dietary changes, exercise, and oral medicine; others will need insulin injections. Controlling blood sugar levels reduces the risk of developing the same kinds of long-term health problems that happen with type 1 diabetes.
Price, Reed, and Papin,  from the Palsson lab, use a method of singular value decomposition (SVD) of extreme pathways in order to understand regulation of a human red blood cell metabolism. Extreme pathways are convex basis vectors that consist of steady state functions of a metabolic network.  For any particular metabolic network, there is always a unique set of extreme pathways available.  Furthermore, Price, Reed, and Papin,  define a constraint-based approach , where through the help of constraints like mass balance and maximum reaction rates , it is possible to develop a ‘solution space’ where all the feasible options fall within. Then, using a kinetic model approach, a single solution that falls within the extreme pathway solution space can be determined.  Therefore, in their study, Price, Reed, and Papin,  use both constraint and kinetic approaches to understand the human red blood cell metabolism. In conclusion, using extreme pathways, the regulatory mechanisms of a metabolic network can be studied in further detail.