6.2 Anaerobic Metabolism: ATP-CP Pathway
The Anaerobic System
The Anaerobic System is an energy system which acts relatively quickly in resynthesizing ATP. While the system is quick to respond to a sudden demand for ATP, the capacity of the system to sustain ATP production is limited. This means that this anaerobic system is only able to provide adequate levels of ATP for a short period of time or short-lived bouts of physical activity, such as weightlifting. One reason this system only provides enough ATP for intense, but short periods, is that it doesn’t utilize oxygen. Anaerobic, by definition, actually refers to “living, active, occurring, or existing in the absence of free oxygen” (Merriam-Webster, n.d.). Within the anaerobic system, two different pathways work to resynthesize ATP to meet the body’s demands: The ATP-CP and Glycolysis pathways.
The ATP-CP Pathway
The ATP–CP pathway (also known as the Phosphagen system or the ATP-PCr system) is the least complex of the three major energy-producing systems because it involves a singular exchange between molecules, which results in the release of energy. The ATP-CP system uses Creatine Phosphate (CP) to convert Adenosine Diphosphate (ADP) into ATP. It does so by removing one phosphate molecule (dephosphorylation) from creatine phosphate and, through creatine kinase, combines it with ADP (which has two phosphate molecules), resulting in ATP (which has three phosphate molecules). The process of adding a phosphate molecule to ADP dephosphorylates ADP into ATP.
In general, the less complex the system, the fewer chemical reactions must take place so ATP can be produced faster. However, these quick reactions are not the most energy efficient, so fewer ATP will be produced per unit of fuel. Since this system is the least complex, it is also the fastest and most immediate, but provides the least amount of ATP. Once the body requires energy, it will once again modify that ATP molecule by breaking off one of its three phosphate molecules (dephosphorylation) and the cycle begins again.
ATP-CP Pathway Summary
- Yields enough ATP for approximately 10 to 15 seconds of intense activity
- Relies on creatine phosphate (CP), which is readily accessible in muscle tissue
- Muscles do not have a large supply of CP, resulting in depleted stores quickly (requires 2 to 5 minutes to resynthesize)
Fitness Fact
While supplements may not be required in every diet, some individuals may benefit from consuming them if their diet isn’t adequate in meeting the body’s demands. CP, from the ATP-CP pathway, is created when the creatine you eat or synthesize is transported to your muscle tissue and phosphorylated in the muscle. This is how your muscles store phosphate that can be used to rapidly dephosphorylate ADP to ATP. CP is sometimes referred to as phosphocreatine (PCr).
“8.3 Phosphagen System (ATP-CP System)” from Nutrition and Physical Fitness by Angela Harter Alger is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted. Modifications: rephrased.
