Phosphorus as Phosphate

Phosphate ion is a major participant in the biological energy cycle through the reactions of mono-, di-, and triphosphates, including one of the most important of these reactions, producing adenosine diphosphate from adenosine triphosphate (see structures in Section 2.3.1, Table 2.2)  

Other important biological manifestations of phosphorus include the pyrophosphate anion, P207 or PPi, and inositol 1,4,5-triphosphate, IP3. Pyrophosphate anions can arise through the following reaction  

Note that equation 5.2 is irreversible and the product AMP will require two phosphorylation steps to reconstitute the high-energy adenosine triphosphate, ATP. Inositol 1,4,5-triphosphate is an important molecule in the cytosol, where it releases calcium ions from storage. It forms part of a series of inositol-phosphate species that mediate calcium ion concentrations inside and outside the cell. 

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Electrolytes that are included routinely in PN admixtures include sodium, potassium, phosphorus (as phosphate), calcium, magnesium, chloride, and acetate. When determining electrolytes in PN admixtures, the patient s renal function always must be taken into account. Typical daily electrolyte maintenance requirements for adults with normal renal function are listed in Table 97-3. 

The average concentration of phosphorus was found to be 3000 ppm. Given the calculated yearly material deposition rate, approximately 11 kg phosphorus would have been contributed each year. Cook and Heizer arrived at an annual deposition rate of 124 kg phosphorus to a site area by a standard population of 100 individuals (28). By utilizing this rate, a population of only nine individuals would have been required to account for the amounts of phosphorus found to be present. Because phosphorus as phosphate is the least mobile of the elements tested, this figure can be considered to represent an absolute minimum permanent population estimate for the site during the period of occupation under consideration. It should be remembered, however, that soil phosphate is also found in occluded forms and in organic combination and that these fractions were not totally measured by the procedure utilized (29). Consequently, the minimum population estimate should be increased, perhaps by as much as 50-60%, to about 15 individuals. 

Fertilizers that contain only one nutrient are called straight fertilizers. Potassium chloride for potassium is an example of a straight fertilizer. Those containing a mixture of the three primary nutrients are called complete, or mixed, fertilizers. The primary nutrients are absorbed by plant roots as simple inorganic ions nitrogen in the form of nitrates (NOp, phosphorus as phosphates (HgPO or HPO ), and potassium as the ion. Organic... 

One important area of medical research Is based on the observation of signals from Compounds that contain phosphorus as phosphate esters (Section 11.10) such as adenosine triphosphate (ATP) and adenosine diphosphate (ADP), are involved in most metabolic processes. Using techniques based on NMR, researchers now have a non-invasive way to follow cellular metabolism. 

Another test for phosphorus (as phosphate) is based on the fact that the phosphomolybdates (and phosphotungstates) form deeply coloured insoluble lakes with triphenylmethane dyes such as methyl violet or malachite green (Chapter 12.8). The procedure is as follows a drop of test solution is placed on a filter paper which is then sprayed with a 1% solution of methyl violet. After about half a minute the paper is then sprayed with a solution of acidified ammonium molybdate and a blue spot develops. This method is sensitive to 1 part in 500,000. 

A 3 mL volume of the oxidizing reagent (or 1 portioning spoon of the commercial oxidation reagent Oxisolv, Merck) is added to SOmL of sample and the mixture is autoclaved for 30min. From the total volume of SSmL (or SOmL if Oxisolv is used) of oxidized sample, 5.0 mL are withdrawn for the determination of total nitrogen as nitrate (nitrite), so that 50 mL (45 mL, respectively) remain for the determination of total phosphorus as phosphate. Die 5 mL portion is diluted to SOmL, and analysed for nitrate manually or by flow-analysis (see Section 10.2.9.6). 

Nitrogen is most commonly found as atmospheric N2 phosphorus as phosphate rock and arsenic, antimony, and bismuth as sulfides or oxides. Antimony and bismuth are also found as free elements. 

Aside from involvements of phosphorus as phosphates in the biochemistry of living systems, perhaps a second approach is to consider vital uses of phosphates in hundreds of products used daily, throughout most societies on Earth. Toy and Walsh s exceptional book. Phosphorus Chemistry in Everyday Livings gives an interesting approach to all forms of phosphorus applications, including DTA, RNA, and ATR Their approach is directed more toward the usefulness of these compounds rather than their safety when in contact with live forms, but it is a simplified, excellent coverage that will not be repeated here. ... 

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