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What Is Creatine Phosphate?

An athlete prepares to run - cells at rest build up their stores of creatine phosphate for use during movement.
An athlete takes off running - creatine phosphate provides a quick source of initial energy for muscle fibers at work.
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  • Written By: Helga George
  • Edited By: Michelle Arevalo
  • Last Modified Date: 11 July 2014
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Creatine phosphate is an organic compound that provides a quick source of energy for muscle fibers to contract when they need an initial burst of energy. It is also found in the brain and provides a similar burst of energy for neurons. Another term for this compound is phosphocreatine, which is abbreviated as PCr or Pcr.

The most common description for the action of creatine phosphate is with muscle fibers. The initial energy for muscle contraction comes from the high-energy compound adenosine triphosphate (ATP). The power of ATP comes from its three high-energy phosphate bonds. Muscle fibers, however, only contain a small reservoir of ATP. Most of their energy store is kept in a pool of creatine phosphate.

The cells also have the precursor to ATP, which is adenosine diphosphate (ADP). This compound has two high-energy bonds. The addition of another high-energy phosphate bond to ADP creates ATP.

Creatine that has a phosphate attached to it is referred to as being phosphorylated, and this phosphate bond is a high-energy one like that of ATP. The phosphorylated creatine transfers its phosphate to ADP to form ATP, leaving unphosphorylated creatine. When the muscle cells have the energy of ATP, they can act in the time it takes for alternate energy sources to be activated. If all of the creatine phosphate is used up, the cells can still produce ATP by an alternate method of energy production that is much less efficient.

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This process is catalyzed by the enzyme creatine phosphokinase, also known as creatine kinase. The reaction is reversible. The enzyme can either add a phosphate to creatine to make creatine phosphate, or remove one to make creatine, depending on the needs of the cell.

When the cells are resting, they build up their stores of creatine phosphate. This is done by removing a phosphate from ATP and adding it to creatine, creating ADP as a by-product in the process. Muscle and brain cells are the classic examples of tissues that utilize this type of system, but other tissues that rapidly use ATP also use creatine phosphate as an energy store. These include spermatozoa and the photoreceptor cells of the retina.

The reversible phosphorylation of creatine phosphate is carried out by one of several different types of creatine kinases. There is one type specialized for muscles (M) and another for the brain (B). Each molecule of creatine kinase is made up of two sub-units, which can be composed of varying combinations of the different types. Creatine kinase of the MB type is assayed clinically in blood tests for emergency patients, and specifically for patients suspected of having had a heart attack or kidney failure.

The creatine kinase test also detects patients with muscle disorders or brain damage. A small percentage of people that take statin drugs to lower their cholesterol will have elevated creatine kinase levels. Low levels can indicate rheumatoid arthritis and alcohol damage to the liver.

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Discuss this Article

anon349967
Post 6

@anon154251: ATP and CP are heavy molecules and would weigh the cell down. It would rather resynthesize ATP after have been separated by ATPase.

anon154251
Post 3

Thanks very much. This really answered many of my questions except one question.

Actually, I am a medical student and our professor asked us: why does the cell needs to store ATP AS creatine phosphate ?? Why not keep it as ATP?

So please I've been thinking and searching for the cause.

I was wondering if you would know the answer. Best regards.

sapphire12
Post 2

@FernValley, while most nutrition experts would agree with you, it does not, unfortunately, matter much to those athletes who are most interested in an easier way to accomplish a goal, and have little concern for the longterm effects of using risky products to enhance physical performance.

FernValley
Post 1

I have hard that creatine products, which provide the user with extra amounts of creatine phosphate and therefore more energy, are on the rise. However, it seems that this, like many chemicals our bodies use, might be best when it is entirely natural, produced in our bodies by consuming other healthy foods.

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