{"id":100,"date":"2022-02-07T21:44:36","date_gmt":"2022-02-08T02:44:36","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/biology1190chemistry\/?post_type=chapter&p=100"},"modified":"2022-04-29T13:49:13","modified_gmt":"2022-04-29T17:49:13","slug":"acids-and-bases","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/biology1190chemistry\/chapter\/acids-and-bases\/","title":{"raw":"Acids and bases","rendered":"Acids and bases"},"content":{"raw":"Pure water dissociates<\/strong> into two ions in solution: a proton (H+<\/sup>) and a hydroxide ion (OH-<\/sup>).\r\n

H2<\/sub>O <=> H+<\/sup> + OH-<\/sup><\/p>\r\nPure distilled water contains an equal amount of protons and hydroxide ions. However, if an acid<\/strong> is added to pure distilled water, then the resulting solution will contain more protons <\/strong>and the solution is acidic<\/strong>. Acids<\/strong> are substances that can donate a proton to solutions. Carbonic acid (H2<\/sub>CO3<\/sub>), for example, is formed in blood when CO2<\/sub> reacts with water in blood plasma. The resulting H2<\/sub>CO3 <\/sub>dissociates in aqueous solution into a proton and bicarbonate (HCO3<\/sub>-<\/sup>).\r\n

CO2<\/sub> + H2<\/sub>O <=> H2<\/sub>CO3<\/sub> <=> H+<\/sup> + HCO3<\/sub>-<\/sup><\/p>\r\nBases<\/strong>, on the other hand, accept protons from solution. Hydroxide and bicarbonate, for example, are bases because they are negatively charged ions that can accept protons from solutions. When bases are added to pure distilled water, the resulting solution will contain less protons relative to bases and will be basic<\/strong>.\r\n\r\nThe acidity of substances is measured on a logarithmic scaled called the [pb_glossary id=\"102\"]pH[\/pb_glossary] scale<\/strong>. The pH scale ranges in value from 0 to 14. These values are the negative logarithm of the concentration of protons [H+<\/sup>] in solution<\/strong>. Therefore, each step along the scale represents a 10-fold change in [H+<\/sup>] in solution. The units of concentration are moles per litre (M).\r\n

pH = -log10<\/sub>[H+<\/sup>]<\/p>\r\nPure distilled water has a pH of 7 and this is considered neutral<\/strong> [neutral = neither acidic nor basic]. Acidic substances have a pH measuring less than <\/em>7. Carbonic acid has a pH of ~4.2, for example. Basic substances have a pH measuring greater than<\/em> 7. Sodium bicarbonate, for example, has a pH of ~8.5.\r\n\r\n

Activity:<\/strong> Calculate the concentration of protons in each biological solution given in the diagram below. Drag and drop the correct concentration under the corresponding solution.<\/div>\r\n\r\n[h5p id=\"69\"]\r\n\r\n[h5p id=\"70\"]\r\n\r\nMost of the solutions inside and outside of cells is kept within a very narrow pH range, generally around neutral pH. For example, blood must be kept between pH 7.35\u20137.45. Serious harm can result from blood pH falling outside of this range.\r\n\r\nSubstances that minimize changes in pH are called buffers<\/strong>. Buffers are molecules that can both donate protons to and accept protons from solutions to keep the pH of that solution constant. Buffers DO NOT necessarily keep the pH of solutions neutral!<\/strong><\/span> Some buffers keep solutions acidic; some keep solutions basic. Buffers simply prevent large changes in pH from occurring when acids or bases are added to solutions.\r\n\r\n \r\n
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Chemistry in the clinic:<\/p>\r\n

Abnormally low<\/em> blood pH results in a condition known as acidosis<\/strong>. Acidosis results in the [pb_glossary id=\"103\"]denaturation[\/pb_glossary] of cellular proteins, disrupting the ability of cells to control solute entry\/exit and to make energy.<\/p>\r\nSimilarly, abnormally high<\/em> blood pH results in alkalosis<\/strong>. Alkalosis decreases the concentration of protons in body fluids as bases accept protons from solution. Alkalosis may also denature proteins and disrupt cellular function.\r\n\r\nIf left untreated, acidosis and alkalosis disrupt cell, tissue, and organ function, potentially leading to death. You may explore acidosis and alkalosis in more detail if you choose to take Biology 1191.\r\n\r\nThe primary regulator of blood pH is an enzyme called carbonic anhydrase in red blood cells. The action of carbonic anhydrase maintains blood buffering and is essential to human body function. This topic will be explored further in lectures about blood and the respiratory system.\r\n\r\n<\/div>\r\n

Summary:<\/h2>\r\n