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( Adenosine triphosphate)
Adenosine-5'-triphosphate (ATP) is a multifunctional nucleotide that is most important as a "molecular currency" of intracellular energy transfer.[1] In this role, ATP transports chemical energy within cells for metabolism. It is produced as an energy source during the processes of photosynthesis and cellular respiration and consumed by many enzymes and a multitude of cellular processes including biosynthetic reactions, motility and cell division. In signal transduction pathways, ATP is used as a substrate by kinases that phosphorylate proteins and lipids, as well as by adenylate cyclase, which uses ATP to produce the second messenger molecule cyclic AMP. The structure of this molecule consists of a purine base (adenine) attached to the 1' carbon atom of a pentose sugar (ribose). Three phosphate groups are attached at the 5' carbon atom of the pentose sugar. ATP is also incorporated into nucleic acids by polymerases in the processes of DNA replication and transcription. When ATP is used in DNA synthesis, the ribose sugar is first converted to deoxyribose by ribonucleotide reductase. ATP was discovered in 1929 by Karl Lohmann,[2] and was proposed to be the main energy-transfer molecule in the cell by Fritz Albert Lipmann in 1941.[3] ATP consists of adenosine — itself composed of an adenine ring and a ribose sugar — and three phosphate groups (triphosphate). The phosphoryl groups, starting with the group closest to the ribose, are referred to as the alpha (a), beta (ß), and gamma (?) phosphates. ATP is highly soluble in water and is quite stable in solutions between pH&_160;6.8–7.4, but is rapidly hydrolysed at extreme pH. Consequently, ATP is best stored as an anhydrous salt.[4] ATP is an unstable molecule and tends to be hydrolysed in water. If ATP and ADP are in chemical equilibrium, almost all the ATP will be converted to ADP. Any system that is far from equilibrium contains potential energy, and is capable of doing work. Biological cells maintain the ratio of ATP to ADP at a point ten orders of magnitude from equilibrium, with ATP concentrations a thousandfold higher than the concentration of ADP. This displacement from equilibrium means that the hydrolysis of ATP in the cell releases a great amount of energy.[5] ATP is commonly referred to as a "high energy molecule"; however this is incorrect, as a mixture of ATP and ADP at equilibrium in water can do no useful work at all.[5] ATP does not contain "high-energy bonds", and any other unstable molecule would serve as a way of storing energy, if the cell maintained its concentration far from equilibrium.[5]
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Adenosine triphosphate Subcategories
Adenosine triphosphate Articles
Vitamin B-2 by David Snape
Riboflavin is a common name for vitamin B-2 and was once known as Vitamin G. You will see Vitamin B-2 described as Riboflavin on the back of vitamin bottles and in other food packaging.
An interesting and curious fact about Riboflavin is that...
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