adenosine triphosphate

adenosine /aden·o·sine/ (ah-den´o-sēn) a purine nucleoside consisting of adenine and ribose; a component of RNA. It is also a cardiac depressant and vasodilator used as an antiarrhythmic and as an adjunct in myocardial perfusion imaging in patients incapable of exercising adequately to undergo an exercise stress test. Symbol A.

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cyclic adenosine monophosphate  a cyclic nucleotide, adenosine 3′,5′-cyclic monophosphate, that serves as an intracellular, and sometimes extracellular, “second messenger” mediating the action of many peptide or amine hormones. Abbreviated 3, cAMP, and cyclic AMP.

adenosine diphosphate  (ADP) a nucleotide, the 5′-pyrophosphate of adenosine, involved in energy metabolism; it is produced by the hydrolysis of adenosine triphosphate (ATP) and converted back to ATP by the metabolic processes oxidative phosphorylation and substrate-level phosphorylation.

adenosine monophosphate  (AMP) adenylic acid; a nucleotide, the 5′-phosphate of adenosine, involved in energy metabolism and nucleotide synthesis.

adenosine triphosphate  (ATP) a nucleotide, the 5′-triphosphate of adenosine, involved in energy metabolism and required for RNA synthesis; it occurs in all cells and is used to store energy in the form of high-energy phosphate bonds. The free energy derived from its hydrolysis is used to drive metabolic reactions, to transport molecules against concentration gradients, and to produce mechanical motion.

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adenosine triphosphate

n.

ATP.

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adenosine triphosphate (ATP),

a compound consisting of the nucleotide adenosine (A) attached through its ribose group to three phosphoric acid molecules (P). Hydrolysis of ATP to adenosine diphosphate (D) releases energy. By coupling a less favorable reaction in the cell with this hydrolysis, the less favorable reaction may proceed, allowing one to think of ATP as the cellular energy currency, especially in muscle.

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adenosine [ah-den´o-sēn]

1. a nucleoside composed of the pentose sugar d-ribose and adenine. It is a structural subunit of ribonucleic acid (RNA). Adenosine nucleotides are involved in the energy metabolism of all cells. Adenosine can be linked to a chain of one, two, or three phosphate groups to form adenosine monophosphate (AMP), adenosine diphosphate (ADP), or adenosine triphosphate (ATP). The bond between the phosphate groups in ADP or the two bonds between phosphate groups in ATP are called high-energy bonds, because hydrolysis of a high-energy bond provides a large amount of free energy that can be used to drive other processes that would not otherwise occur. The energy that is derived from the breakdown of carbohydrates, fats, or proteins is used to synthesize ATP. The energy stored in ATP is then used directly or indirectly to drive all other cellular processes that require energy, of which there are four major types: (1) the transport of molecules and ions across cell membranes against concentration gradients, which maintains the internal environment of the cell and produces the membrane potential for the conduction of nerve impulses; (2) the contraction of muscle fibers and other fibers producing the motion of cells; (3) the synthesis of chemical compounds; (4) the synthesis of other high-energy compounds.

Adenosine.

2. a preparation of adenosine, which acts as a cardiac depressant of automaticity in the sinus node and conduction in the atrioventricular node and as a vasodilator. It is used as an antiarrhythmic and is also used to cause coronary vasodilation during myocardial perfusion imaging in patients who cannot exercise adequately to perform an exercise stress test, administered intravenously.

cyclic adenosine monophosphate a cyclic nucleotide, adenosine 3′,5′-cyclic monophosphate, involved in the action of many hormones, including catecholamines, ACTH, and vasopressin. The hormone binds to a specific receptor on the cell membrane of target cells. This activates an enzyme, adenylate cyclase, which produces cyclic AMP from ATP. Cyclic AMP acts as a second messenger activating other enzymes within the cell. Abbreviated 3′,5′-AMP, cAMP, and cyclic AMP.

adenosine diphosphate (ADP) a nucleotide, adenosine 5′-pyrophosphate, produced by the hydrolysis of adenosine triphosphate (ATP). It is then converted back to ATP by the metabolic processes oxidative phosphorylation, glycolysis, and the tricarboxylic acid cycle.

adenosine monophosphate (AMP) a nucleotide, adenosine 5′-phosphate, involved in energy metabolism and nucleotide synthesis. Called also adenylic acid.

adenosine triphosphatase (ATPase) a term used to refer to the enzymatic activity of certain intercellular processes that split ATP to form ADP and inorganic phosphate, when the energy released is not used for the synthesis of chemical compounds. Examples are the splitting of ATP in muscle contraction and the transport of ions across cell membranes.

adenosine triphosphate (ATP) a nucleotide, adenosine 5′-triphosphate, occurring in all cells, where it stores energy in the form of high-energy phosphate bonds. Free energy is supplied to drive metabolic reactions, to transport molecules against concentration gradients (active transport), and to produce mechanical motion (contraction of myofibrils and microtubules), when ATP is hydrolyzed to ADP and inorganic phosphate or to AMP and inorganic pyrophosphate. ATP is also used to produce high-energy phosphorylated intermediary metabolites, such as glucose 6-phosphate.

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adenosine triphosphate (·deˑ·n·sēn trī·fsˑ·fāt),

n the compound that is hydrolyzed to produce the energy necessary for metabolic processes. Also called
ATP.

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adenosine (den´sēn´),

n a compound derived from nucleic acid, composed of adenine and a sugar, D-ribose. Major molecular component of nucleotides and the nucleic acids.

adenosine monophosphate (AMP),

n an ester, composed of adenine, D-ribose, and phosphoric acid, that affects energy release in work done by a muscle.

adenosine triphosphate (ATP),

n a compound consisting of the nucleotide adenosine attached through its ribose group to three phosphoric acid molecules. Stores energy in muscles, which is released when it is hydrolized to adenosine diphosphate.

Adenoviridae

n a family of unenveloped, 20-sided DNA viruses found in mammals (Mastadenovirus) and birds (Aviadenovirus). The human variety can cause a number of diseases, from conjunctivitis to urinary tract infection.