ATP (adenosine triphosphate) is a nucleotide that is of fundamental importance as a carrier of chemical energy in all living organisms. It consists of adenine linked to D-ribose (i.e. adenosine); the D-ribose component bears three phosphate groups, linearly linked together by covalent bonds (see formula). These bonds can undergo hydrolysis to yield either a molecule of ADP (adenosine diphosphate) and inorganic phosphate or a molecule of AMP (adenosine monophosphate) and pyrophosphate. Both these reactions yield a large amount of energy (about 30.6 kJ mol–1) that is used to bring about such biological processes as muscle contraction, the active transport of ions and molecules across plasma membranes, and the synthesis of biomolecules. The reactions bringing about these processes often involve the enzyme-catalysed transfer of the phosphate group to intermediate substrates, for example by a kinase enzyme.
More on Structure
The ATP molecule is composed of three components. At the centre is a sugar molecule, ribose (the same sugar that forms the basis of RNA). Attached to one side of this is a base (a group consisting of linked rings of carbon and nitrogen atoms); in this case the base is adenine. The other side of the sugar is attached to a string of phosphate groups. These phosphates are the key to the activity of ATP. The Phosphorus Cycle
The fact that ATP is Nature's 'universal energy store' explains why phosphates are a vital ingredient in the diets of all living things. Modern fertilizers often contain phosphorus compounds that have been extracted from animal bones. These compounds are used by plants to make ATP. We then eat the plants, metabolise their phosphorus, and produce our own ATP. When we die, our phosphorus goes back into the ecosystem to begin the cycle again...
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