PHOSPHORIC ACIDS

From Big Medical Encyclopedia

PHOSPHORIC ACIDS — oxygen acids of phosphorus, products of hydration of oxide of phosphorus (V), or P205 phosphoric anhydride.

Anions F. to. — phosphatic groups — are a part of the major organic compounds — nucleotides, nucleic acids (see), phospholipids (see Phosphatides), phosphoproteins (see), phosphoric ethers of carbohydrates (see), vitamins (see), many coenzymes (see) and other connections — the most important participants of a metabolism and energy (see). Phosphorylation (see) — accession of anion F. to. — phosphate — often activates biomolecules (e.g., carbohydrates or nek-ry enzymes), and dephosphorylation brings connections out of an active metabolism of substances. Also cases when, on the contrary, phosphorylation of enzymes transfers them to an inactive state are known. Makroergichesky phosphates (see Vysokoergichesky connections) — ATP and phosphagens (see), napr, creatine phosphate, are used as universal carriers of energy in live systems. Potassium phosphates and sodium are the basic soluble salts orthophosphoric to - you, phosphate-anions belong to the most important anions of live organisms and play an essential role in maintenance of acid-base equilibrium (see), forming the phosphatic buffer HP02 system generating acid equivalents ~/N, P0 ~.

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Eurysynusic metabolite is the inorganic pyrophosphate — anion pyrophosphoric (two-phosphoric) to - you are H4P207. The pyrophosphate is the general link practically of all major metabolic ways in cells of mammals, including and the person. In fabrics the course of the major biosynthetic reactions, such as biosynthesis of coenzymes, electron transfer, acylation and sulphonation, biosynthesis of amino acids (see), lipids (see), phospholipids, polysaccharides (see), steroids (see), terpenes (see), polyamines, nucleinic to - t depends on the maintenance of a pyrophosphate. Hydrolysis of a pyrophosphate to ortho-phosphate is catalyzed by enzyme the inorganic pyrophosphatase (KF 3.6.1.1) regulating concentration of a pyrophosphate in fabrics. The essential role of hydrolysis of a pyrophosphate consists in giving of irreversibility to many metabolic processes, reversible in other conditions.

Several F corresponds to oxide of P205 phosphorus (V). to., however the most important in the metabolic relation is orthophosphoric to - that H3P04, all others F. to. represent the condensed polymeric connections containing from two to 105 atoms of phosphorus (see). In a molecule of all F. to. atom of phosphorus is surrounded with four oxygen atoms located in tops of a tetrahedron:


Orthophosphoric to - that, constitutional formula a cut is stated above, represents colourless hydroscopic crystals with a density of 1,87 g! cm3 and £ °pl 42,35 °. Crystalline hydrate of this is known to - you are H3P04 * • 1/2H20 with * °pl 29,32 °. With water orthophosphoric to - that mixes up in all ratios; density of 85% orthophosphoric to - you at 25 ° make

1,685 g! sm. Orthophosphoric to - that trekhosnovna also forms three rows of salts: normal salts and acid salts with one or with two hydrogen atoms in an acid residue (see Salts). Normal salts orthophosphoric to - you call ortho-phosphates or just phosphates, acid — hydrophosphates: Na3P04, Sa3(r04)) 2 — trekhzameshchen-

ny, or averages, phosphates; Na3HP04, Sanr04 — the two-replaced phosphates, or gpdrofosfata; NaH2P04, Sa (H2P04)2 — monosubstituted phosphates, or dihydrophosphates. Monosubstituted phosphates of a rastvorima in water; from two - and trisubstituted phosphates of a rastvorima only phosphates of alkali metals and ammonium. In water solutions there is a hydrolysis of phosphates.

As a part of rocks and minerals (apatite, phosphorite, viviyenit) phosphates are eurysynusic in the nature, most often in the form of Ca5F(P04) 3 fluorapatite. In soils the content of phosphates reaches 0,2% (in terms of P205). About a bottom the replaced calcium phosphates and magnesium and all potassium phosphates, sodium and ammonium, well water soluble, are most available to plants and microorganisms. Phosphates are a part of the water-soluble phosphoric fertilizers used as sources of phosphorus for agricultural plants. Calcium phosphates are used as mineral top-dressings for domestic animals.

Mix of solutions one - and dvukhzameshchen-ny sodium phosphates (potassium), the so-called phosphatic buffer, supports pH of the environment between 6,0 and 8,0 and is widely used in biochemical researches for stabilization fiziol. pH values in in the vitro systems.

At boiling of solutions orthophosphoric to - you happen its decomposition to formation of the constant boiling mixture (see. And zeotropny mixes) containing 91,1 — 92,1% of P205 (pure to - that contains 72,4% of P205). At a usual temperature orthophosphoric to - that is chemically inert, at high temperatures reacts with the majority of metals and their oxides, affects even gold and quartz, in water solutions at a usual temperature interacts with alkalis. Are known aminophosphoric to - you — substitution products in a molecule F. to. hydroxylic groups amino groups (H0)2P0(NH2) and HOPO(NH2) 2, and also triamide - orthophosphoric to - that (NH)3PO. Organic compounds F are received. to. (see F wasps f) a shouting organic compounds). Nek-rye from them are O B (see. Neuroparalytic toxic agents), are used as insecticides (see) and for other purposes.

In laboratory pure orthophosphoric to - that is received at oxidation of elemental phosphorus nitric to - that, in the industry it is received in the extraction way (during the processing of natural phosphates mix sulfuric and phosphoric to - t) or a thermal way (recovery of natural phosphates to elemental phosphorus with its subsequent burning to P205 and formation of H3P04 a lot of water).

Orthophosphoric to - that is an important semi-product for organic synthesis and receiving technical chemical reactants, is used in the industry (including food), in production of pharmaceuticals, sealing materials in stomatology, etc.

Condensed F. to. depending on a way of connection of the tetrahedral PO3 groups deg'ttsya on polyphosphoric to - you a linear structure of Hn+2Pn03n+i, metaphosphoric to - you with a cyclic structure (HP03) p and ultraphosphoric to - you, consisting of the branched chains and rings forming a net. With increase in number of atoms of phosphorus in a molecule force F. to. increases (see Acids and the bases). Pyrophosphoric to - that is allocated in a crystal look, and three - and tetrapo-lifosforny to - you — in the form of the diluted solutions. In water solutions polyphosphoric to - you are hydrolyzed to orthophosphoric to - you.

In a blood plasma of the person the ratio of NRO and NORO anions sos-

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tavlyat about 4:1. Maintenance fiziol. concentration of inorganic ortho-phosphate, or just phosphate (phosphate of inorganic compounds), in a blood plasma it is carried out by the homeostatic mechanism (see Fosfatemiya). Content of phosphate in cells is about 30 — 40 times higher, than in extracellular liquids. Normal contains in a blood plasma phosphorus of 2,5 — 6 mg! 100 ml, hl. obr. in the form of inorganic phosphate, to-ry it is completely ionized and it is filtered by kidneys. In erythrocytes phosphate contains in the basic as a part of organic compounds, contents to-rykh in a blood plasma is small. Apprx. 15% of phosphate of blood serum it is connected with proteins. The maintenance of a pyrophosphate in a blood plasma makes

1 — 10 µmol! l.

A mineral part of bones of animals and the person consists hl. obr. from salts orthophosphoric to - you Zsa3(r04) hydroxylapatite 2 «Sa (0H)2 and a karbonatapatit ЗСа3(Р04) 2 • Sas03» • H20 (see the Bone). From bones phosphate can come to a blood plasma at decrease in concentration of phosphate in it, and during the strengthening of phosphate in plasma it can be postponed in bones. A significant amount of phosphate in a look a ftorfos-veil of calcium contains in teeth (see Teeth).

Exchange phosphate-anion is closely connected with exchange of calcium (see). Calcium contains in foodstuff hl. obr. in the form of calcium phosphate. If food is eaten in the quantity sufficient for satisfaction of requirements of an organism on the caloric content and protein content, the lack of phosphate of it is excluded. At food there is an inorganic phosphate or phosphate as a part of organic compounds, to-ry in a digestive tract phosphate-anion is released also in the form of inorganic. From 70 to 90% of phosphate of food are soaked up in a small bowel.

Phosphate of hl is excreted. obr. kidneys. With urine 20 — 50 mmol of phosphate a day are removed (the ratio of concentration of phosphate is approximately equal in urine and a blood plasma to 25). Practically all phosphorus of urine is in a type of ortho-phosphate, the quantity to-rogo depends on the content of phosphorus in food (see Fosfaturiya). The increased removal of ortho-phosphate with urine is observed at disturbances of acid-base equilibrium, primary and secondary hyperparathyreosis (see), rickets (see), starvation (see), and also at hard physical activity or consumption with food of excess amount of protein. Removal of phosphate decreases at damage of kidneys, pregnancy (owing to utilization of phosphate the developing fruit) and at diarrhea (owing to disturbance of absorption of phosphate in intestines). Administration of glucose or insulin causes temporary reduction of release of phosphate since at the same time its concentration in a blood plasma decreases. Almost insoluble Sa3(r04) phosphates 2 ii MgNH4P04 are a part of urinary stones (see).

In live organisms also inorganic polyphosphates — linear polymers are found, in to-rykh the remains orthophosphoric to - you are connected among themselves by energy-rich fosfo-angidridny bonds. The number of such remains can reach hundreds and even thousands. Such high-molecular polyphosphates are found in bacteria, fungi; microorganisms in nek-ry conditions accumulate significant amounts of polyphosphates (e.g., at yeast their abundance reaches 10 — 20% of dry weight). In small amounts (10 — 100 mkg! of crude fabric) polyphosphates contain in tissues of the highest animals and plants. High-molecular phosphates are used as donors of phosphate and energy for the major fiziol. processes. The role of polyphosphates in energy and phosphoric balance at microorganisms is especially big.

During the studying of phosphorus compounds of an organism in laboratory they are divided into phosphates, insoluble in trichloroacetic to - those (phospholipids, phosphoproteins, nucleinic to - you), and phosphates, soluble in trichloroacetic to - those. At short-term hydrolysis of the last in salt to - those at 100 ° inorganic kislotolabilny phosphate of nukleozidtrifosfat, creatine phosphate, glyukozo-1-phosphate is released and there is in the connected form a kpslo-tostabilny phosphate a glyukozo-6-fos-veil, ribozo-5-phosphate, glitsero-

3 phosphates.

In clinic the term «phosphate» often is the collective name of the compounds of phosphorus defined

in the form of inorganic phosphate irrespective of their origin. These connections transfer to a form of the ionized phosphate, define by methods of definition of phosphorus, hl. obr. photometric (see Photometry) or hromatografichesk (see the Chromatography) also recalculate for phosphorus or P205. Bibliography: At l and I am H. M and Komi with-sarenko S. V. An inorganic pyrophosphate, its structural analogs and inorganic pyrophosphatase, in book: At the joint venture. biol. chemical, under the editorship of B. N. Stepanenko, etc., t. 22, page 195, M., 1982; Kor Bridge D. Fosfor, the lane with English, M., 1982. See also bibliogr. to St. Phosphorus.

N. V. Gulyaeva.

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