They are necessary for the building and rebuilding of tissues and cells. Enzymes are catalysts that influence all life systems in our bodies, and are produced by living cells but are capable of acting independently. They are complex proteins that can induce chemical changes in other substances without being changed themselves. The protein portion is determined by the genetic code. The vitamin portion is usually called the coenzyme.
Every cell contains a part called the mitochondria , which acts like an engine.
The cells do not use the nutrients consumed in the diet for their immediate supply of energy. In turn, the energy in food is extracted to build more ATP . The potential energy stored in the ATP molecule represents chemical energy made in the cell as it is needed, and is responsible for 95 percent of all cellular energy throughout the body. Although ATP serves as the energy current for all cells, its quantity is limited. This would provide only enough energy to sustain strenuous activity, such as running as fast as you can, for 5 to 8 seconds.