Adenosine diphosphate formation from

Effect on blood Platelets are the important factors in thrombus formation and aspirin has been shown to inhibit platelet aggregation. They reduce the blood prothrombin level by inhibition of prothrombin synthesis and prothrombin time is prolonged. The aspirin suppresses the synthesis of thromboxane (TXA ) in the platelets. They also prolong the bleeding time due to prevention of platelet aggregation which may be due to inhibition of release of adenosine diphosphate (ADP) from the platelets by salicylates. 

The structure and formation of ATP. (A) The chemical structure of adenosine triphosphate (ATP). "C" indicates carbon, "N" nitrogen, "O" oxygen, "H" hydrogen and "P" phosphorus. Note the negative charges on the phosphate groups (PO3 ). (B) ATP can be formed from adenosine diphosphate (ADP). 

The formation of a platelet aggregate requires the recruitment of additional platelets from the blood stream to the injured vessel wall. This process is executed through a variety of diffusible mediators which act through G-protein-coupled receptors. The main mediators involved in this process are adenosine diphosphate (ADP), thromboxane A2 (TXA2), and thrombin (factor Ila). These mediators of the second phase of platelet activation are formed in different ways. While ADP is secreted from platelets by exocytosis, the release of TXA2 follows its new formation in activated platelets. Thrombin can be formed on the surface of activated platelets (see Fig. 2). 

In the preceding sections the conversion of purines and purine nucleosides to purine nucleoside monophosphates has been discussed. The monophosphates of adenosine and guanosine must be converted to their di- and triphosphates for polymerization to RNA, for reduction to 2 -deoxyribonucleoside diphosphates, and for the many other reactions in which they take part. Adenosine triphosphate is produced by oxidative phosphorylation and by transfer of phosphate from 1,3-diphosphoglycerate and phosphopyruvate to adenosine diphosphate. A series of transphosphorylations distributes phosphate from adenosine triphosphate to all of the other nucleotides. Two classes of enzymes, termed nucleoside mono-phosphokinases and nucleoside diphosphokinases, catalyse the formation of the nucleoside di- and triphosphates by the transfer of the terminal phosphoryl group from adenosine triphosphate. Muscle adenylate kinase (myokinase)... 

Mechanism of Action An aggregation inhibitor that inhibits the release of adenosine diphosphate from activated platelets, which prevents fibrinogen from binding to glycoprotein Ilb/IIIa receptors on the surface of activated platelets. TherapeuticEffect Inhibits platelet aggregation and thrombus formation. 

The oxygen formed clearly comes from H20 and not from C02, because photosynthesis in the presence of water labeled with lgO produces oxygen labeled with 180, whereas carbon dioxide labeled with 180 does not give oxygen labeled with 180. Notice that the oxidation of the water produces two electrons, and that the formation of NADPH from NADP requires two electrons. These reactions occur at different locations within the chloroplasts and in the process of transferring electrons from the water oxidation site to the NADP reduction site, adenosine diphosphate (ADP) is converted to adenosine triphosphate (ATP see Section 15-5F for discussion of the importance of such phosphorylations). Thus electron transport between the two photoprocesses is coupled to phosphorylation. This process is called photophosphorylation (Figure 20-7). 

An essentially electrochemical model for metabolism and the formation of adenosine tri-phosphate from adenosine diphosphate was suggested by R. J. P. Williams at Oxford University in 1959.18 It is shown in Fig. 14.40. 

The primary medium for free energy storage in living cells is adenosine triphosphate (ATP). Its formation from adenosine diphosphate (ADP) is not spontaneous ... 

The three tissue enzymes known to participate in formation of the phosphate esters are (1) thiaminokinase (a pyro-phosphokinase), which catalyzes formation of TPP and adenosine monophosphate (AMP) from thiamine and adenosine triphosphate (ATP) (2) TPP-ATP phosphoryl-transferase (cytosoHc 5"-adenylic kinase)which forms the triphosphate and adenosine diphosphate from TPP and ATP and (3) thiamine triphosphatase, which hydrolyzes TPP to the monophosphate. Although thiaminokinase is widespread, the phosphoryl transferase and membrane-associated triphosphatase are mainly in nervous tissue. 

Irradiation of water leads to formation of (HO) . By contrast, in the brain, strong water-soluble electron donors (DH) such as nicotinamide adenine dinucleotide phosphate (NADPH), catechin, hydroquinone, ascorbic acid or glutathione (L-y-glutamyl-L-cysteinyl-glycine GSH) can promote formation of (HO) from H2O2 in the presence of Cu+ or some iron complexes (e.g. Fe -adenosine diphosphate complexes) according to Eqs. (15) and (16) (Florence, 1984 Kadiiska et al., 1992). 

We may suppose that the photosynthetic organisms learned to recombine products of the photochemical oxidation-reduction reaction in a useful way. The energy released by this recombination was used to bring about the formation of the biological acid anhydrides, such as adenosine triphosphate (ATP) from inorganic phosphate, and organic phosphates such as adenosine diphosphate (ADP). 

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