adenosine triphosphate
adenosine triphosphate (ATP): sometimes called ‘the spark of life’. Any bodily movement powered by voluntary or involuntary muscle; other cellular movements such as the migration of white blood cells; the swimming of sperm; and even the contraction of hair cells in the inner ear need a supply of free energy. But so too does the transport of molecules from one body compartment to another, and the synthesis of all biomolecules required for growth, repair, or maintenance of bodily functions. ATP is an energy-rich molecule, which releases free energy when it is broken down to either ADP (adenosine diphosphate) or AMP (adenosine monophosphate). This reaction is usually stimulated by enzymes collectively called ATP-ases. Even a sedentary adult breaks down 40 kg/day of ATP and the rate of consumption rises to 0.5 kg/minute during strenuous exercise. But cells do not store large amounts of ATP, so it must be continually replenished. The energy that must be put back to reconstruct ATP from ADP is supplied by the oxidation (burning) of foods.
Alan W. Cuthbert
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adenosine triphosphate