ATP Energy's Building Block

Let's do another quick review.As you learned in Lesson 4, the energy that drives muscle contraction comes from a substance called adenosine triphosphate or ATP. ATP is produced from the glucose in the muscle cell.Although cells can store some small amounts of ATP, a working muscle uses up the stores quickly in two to three seconds. Therefore, the rate at which a muscle produces ATP determines how much energy that cell can produce before it is tired.As part of the process of supplying energy to active muscles, ATP is converted to ATP, which is a lower compound that can be reconverted into ATP .If the muscles aren't working too hard, the cell's mitochondria use oxygen to regenerate ATP from ATP. The mitochondria oxidize fuel in the forms of carbohydrates, fats, and proteins, to produce energy, yielding carbon dioxide and water as by products of the process. However, if the activity lasts a longer period of time and is at a certain level of intensity, the aerobic system can't keep up with the demands for ATP. At this point, the body uses different methods for producing energy.We'll take an in depth look at anaerobic energy systems later in this lesson.