ATP, ADP: What Does It All Mean
When it comes to understanding various things in health and exercise science, there are few basic principles that people must know. One of them is basic energy conversions in the body and how that helps various processes. In this article, I'll aim to both simplify it as much as possible but also give you as much information as I can. Whether you're an aspiring S&C coach or your a student who does science in school you can benefit from this.
Figure 1. Image showing how ATP and ADP reactions are reversible and the constant flux between stored and liberated energy.
ATP is the energy currency of the human body (and other living organisms for that matter). It is responsible for powering any process that requires energy including muscle contraction, synthesis of other molecules from smaller compounds (protein synthesis), transport of substances across membranes etc. Some of these are important for us to know right now, some will make more sense later on.
ATP stands for - adenosine triphosphate. It is three phosphate groups combined to adenosine. ATP is the stored unit of energy. To release this stored energy, the third phosphate must be removed from the link. To do this we need a water molecule and an enzyme called ATPase. This reaction liberates the energy, converting it into ADP (adenosine diphopshate + energy) and allows the cells to use it, the process in which it is used is dependent on the cells in which it takes place. For example, if this reaction took place in the muscle cell, then the energy released would be used to fuel muscle contractions.
This reaction is reversible. This means that the ADP produced by the liberation of energy can be converted back into ATP. This is also known as ATP recycling and is a process that in continually ongoing within the cells. ATP stores are limited so the better and more efficient that the cells are at recycling ATP stores then the more work the cell can do. This reversible reaction involves taking an ADP molecule and using some energy to add another phosphate group onto the chain to create ATP with the help of an enzyme called ATP synthase. The energy systems article series goes some way to shedding light on the various ways in which ATP is generated.
ATP stands for - adenosine triphosphate. It is three phosphate groups combined to adenosine. ATP is the stored unit of energy. To release this stored energy, the third phosphate must be removed from the link. To do this we need a water molecule and an enzyme called ATPase. This reaction liberates the energy, converting it into ADP (adenosine diphopshate + energy) and allows the cells to use it, the process in which it is used is dependent on the cells in which it takes place. For example, if this reaction took place in the muscle cell, then the energy released would be used to fuel muscle contractions.
This reaction is reversible. This means that the ADP produced by the liberation of energy can be converted back into ATP. This is also known as ATP recycling and is a process that in continually ongoing within the cells. ATP stores are limited so the better and more efficient that the cells are at recycling ATP stores then the more work the cell can do. This reversible reaction involves taking an ADP molecule and using some energy to add another phosphate group onto the chain to create ATP with the help of an enzyme called ATP synthase. The energy systems article series goes some way to shedding light on the various ways in which ATP is generated.
Now, you may be thinking where does the cell get the energy to produce these new ATP molecules? Well it can be done one of three ways. The body has three energy systems, they are always in constant flux between each other depending on the demands of the activity. These three systems are:
- PCr system - Also often referred to as the phosphocreatine system. This system is relied upon for short bursts of activity (10-15 seconds).
- Glycolytic system - mainly for exercise durations less than two minutes. This system does not rely on oxygen to assist in the breakdown of glucose to fuel activity.
- Oxidative system - This system occurs in the presence of oxygen and is the long term fuel source for activity. It also yields the most ATP molecules as it takes the longest.
While this short article is not going to go into detail about cellular respiration and how different energy systems are relied upon for different exercise/activities, it has given you a little introduction into what ATP is and what it does.
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