Acidic solution stomach acid

The activity of an enzyme varies considerably with acidity and there is generally a marked optimum pH for each enzyme. Thus pepsin of the stomach has an optimum pH of 1 4, i.e., it works best in a decidedly acid medium. It is inactive in neutral or alkaline solutions and the latter rapidly destroy it. 

Sodium dithionite is considered only moderately toxic. The solution is reported to have an LD q (rat, oral) of about 5 g/kg. As with sulfites, fairly large doses of sodium dithionite can probably be tolerated because oxidation to sulfate occurs. However, irritation of the stomach by the Hberated sulfurous acid is expected. As a food additive, sodium dithionite is generally recognized as safe (GRAS) (367). 

The sodium and potassium salts are veiy soluble in water but they are hydrolysed in solution, at a temperature-dependent rate, to the corresponding penicilloic acid (Fig. 5.3 A see also Fig. 9.3), which is not antibacterial. Penicilloic acid is produced at alkaline pH or (via penieillenic acid Fig. 5.3B) at neutral pH, but at acid pH a molecular rearrangement oeeurs, giving penillic acid (Fig. 5.3C). Instability in acid medium logically precludes oral administration, since the antibiotic may be destroyed in the stomach for example at pH 1.3 and 35°C methicillin has a half-life of only 2-3 minutes and is therefore not administered orally, whereas ampicillin, with a half-life of 600 minutes, is obviously suitable for oral use. 

It is also essential to have a clear understanding of the analyte or property being measured. For example, an analyst may be studying the amount of lead present in paint used on toys. One possibility would be to use a method which determines the total amount of lead present. Alternatively, the analyst may be interested in the amount of lead that is released from a paint sample taken from a toy when it has been extracted with a stomach-acid simulant. In both cases, the end measurement is the same - the concentration of lead in a solution. However, the results from the two approaches would be very different. In the first case, the sample will have been digested with a strong acid solution which should release all of the lead present in the sample. In the second case, we would expect the results to be lower as the method is designed to estimate the amount of lead released under particular conditions. The second type of method is sometimes referred to as an empirical method. This is a method where the result produced is entirely dependent on the analytical method. In the above example, if the... 

In this experiment the neutralizing power of various antacids will be determined. Antacids contain basic compounds that will neutralize stomach acid (stomach acid is HC1). The amount of base in the antacid tablets will be determined by an acid-base titration. It is a back titration method. This method is used because most antacids produce carbon dioxide gas, which can interfere with the titration. By initially adding an excess of acid, one can drive off the C02 by boiling the solution before titrating the excess acid. There are many brands of commercial antacids with various ingredients. A few of the common ones are listed below ... 

Exposure of the skin to a high concentration of the gas or to a concentrated solution of the liquid (hydrochloric acid) will cause burns repeated or prolonged exposure to dilute solutions may cause dermatitis. Erosion of exposed teeth may also occur from repeated or prolonged exposure. Although ingestion is unlikely, hydrochloric acid causes severe burns of the mouth, esophagus, and stomach with consequent pain, nausea, and vomiting. ... 

Because of the sensitive nature of most biopharmaceuticals, their dosage forms are limited to injectable solutions. Therapeutic proteins cannot pass the acidic milieu of the stomach undamaged, nor are they absorbed through the intestinal wall. Although work on alternatives such as inhalers is underway (the first commercial application is an insulin inhaler), injection remains the predominant option for administering sensible biopharmaceuticals. 

The drug solution of weak acid in the stomach (pH = 1.0 acidic) will be in more unionized form, which is more lipid soluble and gets more easily absorbed in the stomach. 

The activation of pepsin from its zymogen pepsinogen occurs by a different mechanism. In this case, the pH of the environment plays a decisive role. In the strongly acidic milieu of the stomach cleavage of a 44 amino acid peptide occurs from the inactive precursor pepsinogen. The activation is intramolecular and depends on the pH of the solution. 

Just as aspirin continues to provide the same benefits as a century ago, it also produces some of the same problems. The major problem with aspirin is that it can upset the stomach. In the acidic environment of the stomach, aspirin can diffuse through the protective mucus lining and rupture cells and produce bleeding. Under normal doses, the amount of blood loss in most individuals is only a milliliter or two, but in some individuals who take heavy doses, gastrointestinal bleeding can be severe. To counteract this side effect, manufacturers include an antacid such as aluminum hydroxide and call the aspirin a buffered aspirin. This term is misleading because the antacid does not buffer the solution rather, it neutralizes some of the acidic effects of the aspirin. Another type of aspirin, called enteric aspirin, dissolves in the intestines where the environment is more basic. 

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