A myosin is a tiny, microscopic molecule that uses chemical energy to perform a specific action. They can be thought of as the batteries that power the muscles of the body, responsible for both voluntary and involuntary movements. These molecules take the energy that is stored in cells and transform it into energy.
Myosins first use adensosine triphosphate (ATP) to power each movement. Made up of carbon, nitrogen, oxygen and phosphorus, ATP is the most common molecule created from the breakdown of dietary energy sources like fats and sugars. Large amounts of ATP are required to power the movement of the muscles, and it is quickly expended. Once that happens, myosins are equipped to look for energy sources elsewhere in the body.
Phosphocreatine is the second energy source that myosins can process and convert into energy. Rather than using it in its normal form, myosins first turn the phosphocreatine into ATP. This also runs out quickly, though, and the myosins then begin to process glycogen and the glucose that is stored within. Once the glycogen is gone, the muscles will tire; this is why the body can only sustain certain types of vigorous activity such as sprinting or jumping for a very brief amount of time.
There is a bond within every ATP molecule that the myosin breaks in order to access the energy. It isn't the breaking of this phosphate to phosphate bond that gives the myosin its energy, but instead the breaking down of the phosphate itself when the myosin cleaves into the molecule after breaking the chemical bond. When this release happens, the myosin releases the energy and grabs onto a new source of ATP.
Every individual myosin has a long tail and a head that is split into two sections. The cleft between these two heads is where the ATP or glycogen enters the molecule. The tail is the part of the molecule that processes the energy. On one side of the molecule is a helix-shaped attachment that amplifies the energy that is released from the ATP.
Each myosin is microscopic, and converts only a tiny amount of ATP or glycogen into movement. Each muscle in the body contains trillions of these myosins, and they all work together to perform all everyday actions. Within every muscle, the long tail of a single mysoin is bound to 299 others to create a larger, longer filament that is designed to further amplify the energy created by the myosin.