Creatine is another "high energy" storage source comparable to ATP. One of its primary funtions is to provide "backup" to ATP hydrolysis in muscle. When muscles are under heavy work load, the ATP is used up quickly. creatine-phophate can regenerate the ADP that is formed back to ATP without having to recycle the ADP through the mitochindria
While your muscles are at rest, The ATP concentration is high relative to the concentration of ADP. The reaction at this time tends toward generating phosphocreatine. Then as you begin to work your muscles hard, this reverses - allowing the phosphocreatine to quickly re-generate ATP.
Creatine is not a vitamin in the classic sense. We synthesize it ourselves from the common amino acids Arginine and Glycine. The pathway is described at the same Wikipedia page. We will not discuss this further in this course.
Nevertheless, you can buy creatine at the store. It is typically used by body builders who claim that it gives them more endurance and better force generation. There have been concerns raised regarding safety of excessive creatine consumption. Most have been alleviated - except one. It seems that many of the brands contain toxic impurities such as heavy metals.
