Tag Archives: ATP


The mitochondrion is an important cell organelle. The most important function of a mitochondrion is to generate ATP. The mitochondria are therefore often called the cells’ power plants. Mitochondria are present in almost almost all cells, but the number of mitochondria in a cell depends on the amount of energy the cell needs, and therfore large numbers of mitochondria are present in muscle fibers. The concentration of mitochondria is dependent on muscle fiber type and the demands placed upon the muscle. In addition the number of mitochondria in a muscle fiber adapts to endurance training or low intensity high repetition resistance exercise, which both target the aerobic system and stimulate the mitochondria to replicate.

Aerobic System

The aerobic system, also called the oxidative system (aerobic means a proces which functions with the aid of oxygen) is the most important source of ATP in rest and during lower intensity exercise. In this system ATP is generated from both carbohydrates and fats, but when carbohydrate stores are depleted protein can also be used. Depending on the intensity of exercise, a certain ratio of carbohydrates and fats is used. At rest this ratio is around 70% fat and 30% carbohydrates. When exercise starts, the use of fat as an energy substrate decreases and carbohydrate use increases with the increase in intensity. When intensity rises to 100% VO2max, almost all ATP will be generated from carbohydrates.


Adenosine triphosphate (ATP) is the fuel that provides energy for all energy demanding cellular processes. ATP is the fuel that allows contraction of the muscles. Below is the equation which depicts the reaction occuring within the muscles and makes contraction possible. This reaction is reversible so that ATP supply can be resynthesized.