Bicarbonate membrane

Coupled transport of hydrogen sulfide through the same carbonate/bicarbonate membrane is shown in Figure 11.24 [26], The overall reaction is simple... 

Suchdeo, S.R. and J.S. Schultz. "The permeability of gases through reacting solutions the carbon dioxide-bicarbonate membrane system." Chemical Engineering Science 29 (1974) 13-23. 

Uranium can enter the human body orally, by inhalation, and through the skin and mucous membranes. Uranium compounds, both soluble and insoluble, ate absorbed most readily from the lungs. In the blood of exposed animals, uranium occurs in two forms in equiUbrium with each other as a nondiffusible complex with plasma proteins and as a diffusible bicarbonate complex (242). 

When a potential is appHed across the ceU, the sodum and other cations are transported across the membrane to the catholyte compartment. Sodium hydroxide is formed in the catholyte compartment, because of the rise in pH caused by the reduction of water. Any polyvalent cations are precipitated and removed. The purified NaOH may be combined with the sodium bicarbonate from the sodium dichromate process to produce soda ash for the roasting operation. In the anolyte compartment, the pH falls because of the oxidation of water. The increase in acidity results in the formation of chromic acid. When an appropriate concentration of the acid is obtained, the Hquid from the anolyte is sent to the crystallizer, the crystals are removed, and the mother Hquor is recycled to the anolyte compartment of the ceU. The electrolysis is not allowed to completely convert sodium dichromate to chromic acid (76). Patents have been granted for more electrolytic membrane processes for chromic acid and dichromates manufacture (86). 

Optimized modern dry scrubbing systems for incinerator gas cleaning are much more effective (and expensive) than their counterparts used so far for utility boiler flue gas cleaning. Brinckman and Maresca [ASME Med. Waste Symp. (1992)] describe the use of dry hydrated lime or sodium bicarbonate injection followed by membrane filtration as preferred treatment technology for control of acid gas and particulate matter emissions from modular medical waste incinerators, which have especially high dioxin emissions. 

As CO2 passes through the membrane, while bicarbonate is rejected, the product water tends to be acidic and may need pH correction. 

Acid addition is commonly used to convert bicarbonates into the more soluble sulfate salts to reduce the alkalinity of the RO RW, which in turn modifies the brine reject water LSI. Sometimes it is required to maintain the pH level within membrane limits. Additionally, it may be used in conjunction with a reduced dosage of antiscalent chemical to reduce the overall chemical treatment costs. 

Carbon dioxide devices were originally developed by Severinghaus and Bradley (59) to measure the partial pressure of carbon dioxide in blood. This electrode, still in use today (in various automated systems for blood gas analysis), consists of an ordinary glass pH electrode covered by a carbon dioxide membrane, usually silicone, with an electrolyte (sodium bicarbonate-sodium chloride) solution entrapped between them (Figure 6-17). When carbon dioxide from the outer sample diffuses through the semipermeable membrane, it lowers the pH of the inner solution ... 

Figure 29-9. Reactions and intermediates of urea biosynthesis. The nitrogen-containing groups that contribute to the formation of urea are shaded. Reactions and occur in the matrix of iiver mitochondria and reactions , , and in iiver cytosoi. COj (as bicarbonate), ammonium ion, ornithine, and cit-ruiiine enter the mitochondriai matrix via specific carriers (see heavy dots) present in the inner membrane of iiver mitochondria.

Patients with acute hyperkalemia usually require other therapies to manage hyperkalemia until dialysis can be initiated. Patients who present with cardiac abnormalities caused by hyperkalemia should receive calcium gluconate or chloride (1 g intravenously) to reverse the cardiac effects. Temporary measures can be employed to shift extracellular potassium into the intracellular compartment to stabilize cellular membrane effects of excessive serum potassium levels. Such measures include the use of regular insulin (5 to 10 units intravenously) and dextrose (5% to 50% intravenously), or nebulized albuterol (10 to 20 mg). Sodium bicarbonate should not be used to shift extracellular potassium intracellularly in patients with CKD unless severe metabolic acidosis (pH less than 7.2) is present. These measures will decrease serum potassium levels within 30 to 60 minutes after treatment, but potassium must still be removed from the body. Shifting potassium to the intracellular compartment, however, decreases potassium removal by dialysis. Often, multiple dialysis sessions are required to remove potassium that is redistributed from the intracellular space back into the serum. 

Normally, the number of anions and cations in each fluid compartment are equal. Cell membranes play the critical role of maintaining distinct ICF and ECF spaces which are biochemically distinct. Serum electrolyte concentrations reflect the stores of ECF electrolytes rather than that of ICF electrolytes. Table 24-4 lists the chief cations and anions along with their normal concentrations in the ECF and ICF. The principal cations are sodium, potassium, calcium, and magnesium, while the key anions are chloride, bicarbonate, and phosphate. In the ECF, sodium is the most common cation and chloride is the most abundant anion while in the ICF, potassium is the primary cation and phosphate is the main anion. Normal serum electrolyte values are listed in Table 24—5. 

Gutknecht, J. Bisson, M. A. Tosteson, F. C., Diffusion of carbon dioxide through lipid bilayer membranes. Effects of carbonic anhydrase, bicarbonate, and unstirred layers, J. Gen. Physiol. 69, 779-794 (1977). 

Figure 11 Schematic of mucosal membrane sodium-proton exchanger and chloride-bicarbonate exchanger responsible for pH homeostasis in enterocyte cytosol. Microclimate pH is maintained by mucosal slowing of proton diffusion away from the lumenal membrane.

Biochemical and molecular cloning studies indicate the existence of nine separate and unique forms of adenylyl cyclase (AC), which comprise a distinct enzyme family, referred to as AC1-AC9 [1, 2]. These members of the adenylyl cyclase superfamily are all membrane-bound. There is also an additional soluble form, sAC, that has catalytic activity similar to the others but is genetically the most divergent member of the family. All the membrane-bound forms of adenylyl cyclase are activated by the stimulatory G protein Gas (see Ch. 19), and all with the exception of AC9 are stimulated by forskolin. The soluble form sAC is not stimulated by either Gas or forskolin but is sensitive to bicarbonate levels. All known forms of... 

Since hematin inhibits Taq polymerase, it is absolutely essential to eliminate red blood cell contamination. Selective lysis of red blood cells can be accomplished with a buffer mixture consisting of 155 mM ammonium chloride, 10 mM potassium bicarbonate, and 0.1 mM EDTA adjusted to pH 7.4. Alternatively, the cytoplasmic membrane of all cells can be dissolved with a buffer mixture containing the non-ionic detergent Triton-X 100, leaving behind nuclei of white blood cells from which DNA can be extracted. However, this technique will result in the loss of cytoplasmic DNA to the supernatant, and hence will not be able to extract mitochondrial DNA (B11). 

Carbonic anhydrase (CA, also called carbonate dehydratase) is an enzyme found in most human tissues. As well as its renal role in regulating pH homeostasis (described below) CA is required in other tissues to generate bicarbonate needed as a co-substrate for carboxylase enzymes, for example pyruvate carboxylase and acetyl-CoA carboxylase, and some synthase enzymes such as carbamoyl phosphate synthases I and II. At least 12 isoenzymes of CA (CA I—XII) have been identified with molecular masses varying between 29 000 and 58 000 some isoenzymes are found free in the cytosol, others are membrane-bound and two are mitochondrial. 

Cytosolic CA II is widespread through tissues, the kidney possesses CA IV which is anchored to the cell membrane of the luminal PCT brush border by linkage with a membrane phospholipid, glycosylphosphatidylinositol. Such luminal positioning allows the enzyme to act upon filtered bicarbonate ions as they enter the tubule. 

This measurement is actually one of pH. The principle involves the measurement of the pH of a bicarbonate solution separated from the sample by a CCh-permeable membrane. CO2 diffuses in (or out) and changes the bicarbonate solution pH in proportion to the pCCh in the sample. This method has all the drawbacks of pH measurement with a glass electrode. The problems associated with this method perhaps explain why it is not widely used in biochemical engineering laboratories and process streams despite its considerable metabolic significance 5 ... 

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