Adenosine Triphosphate (ATP) The cell's energy currency


Adenosine Triphosphate





Definition





The energy currency of all cells in a nucleotide called adenosine triphosphate (ATP). ATP provides central role as the energy currency in all organisms.









Components of Adenosine Triphosphate





Each and every Adenosine Triphosphate molecule contains three parts






  1. Adenine: An organic molecule composed up of two carbon-nitrogen rings.

  2. Ribose: A five carbon sugar

  3. Three phosphate groups in a linear chain





Functions of Adenosine Triphosphate





For most of the functions Adenosine Triphosphate is a major energy source. For example:






  1. The synthesis of macro-molecules (DNA,RNA, and Proteins).

  2. Movement.

  3. Transmission of nerve impulses.

  4. Active Transport.

  5. Endocytosis and exocytosis etc.





Adenosine Triphosphate as energy currency






  • The covalent bond connecting phosphates is indicated by "Tilde" symbol. It is a high energy bond. However, the energy is not localized in the bond itself. It is a property of entire molecule. It is simply released as the phosphate bond breaks. These bonds have low activation energy and break easily. The breaking of one bond releases about 7.3K calories (7300 calories) per mole of Adenosine Triphosphate.





ATP+H2O      ADP+Pi+energy (7.3Kcal/mole)






  • The energy from Adenosine Triphosphate is sufficient  to drive most of the cell's endergonic reactions. In a typical energy reaction, only the outer most of two high-energy bonds breaks. When this happens, Adenosine Triphosphate becomes Adenosine Diphosphate (ADP). In some cases, Adenosine Di-phosphate is hydrolyzed to Adenosine Mono-phosphate (AMP).





ADP+H2O           AMP+Pi+energy (7.3Kcal/mole)





Recycling of Adenosine Triphosphate





Adenosine Triphosphate (ATP) is constantly cleaved into Adenosine Di-phosphate (ADP) plus phosphate to start the cells many energy requiring process. Thus enabling the animals to do biological work. However, Adenosine Triphosphate cannot be stored for long. Once formed, ATP lasts only a seconds before it used to perform biological work. Thus cells constantly recycle Adenosine Diphosphate (ADP). With the energy derived from food stuffs and from stored fats and starches, Adenosine Di-phosphate recombines to form Adenosine Triphosphate, with 7.3Kcal of energy per mole contributed to each newly formed high-energy phosphate bond.






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