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What chemical compounds might be present in drinking water?
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3.3.2 Adenosine triphosphate

After deoxyribonucleic acid, DNA (which is a phosphodiester), adenosine triphosphate (ATP, Structure 10), is probably the most important phosphorus-containing molecule in the human body.

Structure 10

ATP is used to drive many biochemical reactions and cellular processes that require the input of energy; these include cell division and muscle contraction.

Energy is obtained from ATP when it is hydrolysed to adenosine diphosphate (ADP) and free phosphate ions. Equation 31 is thermodynamically favourable, having a free energy change, cap delta sub r times cap g super circle with horizontal bar, of about −140 kJ mol−1.

Note that when bonded together the adenine and ribose rings are referred to as adenosine.

Equation 31

ATP is synthesised by the reverse process - the addition of phosphate to ADP. The energy input for this reaction comes from the breakdown of organic fuel molecules, such as glucose.

The negative charge on ATP, ADP and DNA is counterbalanced by cations, usually Mg2+. Hence, both ATP and DNA may be regarded as magnesium complexes.