Anatomy & Physiology I and II

Anatomy & Physiology Study Guide because some of the water molecules dissociate spontaneously, releasing cations and anions. The hydrogen ion concentration in the body is defined by the pH level . Although pure water has a pH of seven, solutions display a wide range of pH values, depending on the nature of the solutes involved: • A solution with a pH of seven is neutral because it contains an equal number of hydrogen and hydroxide ions. • A solution with a pH below seven is considered acidic because it contains more hydrogen ions than hydroxide ions. • A solution with a pH above seven is basic or alkaline, meaning that it has more hydroxide ions than hydrogen ions. The pH of blood normally ranges from 7.35-7.45. Abnormal fluctuations in pH can damage cells and tissues by changing protein shape, breaking chemical bonds, and altering cellular functions. Acidosis is an abnormal physiological state caused by low blood pH (below 7.35); a pH below seven can lead to coma or death. Alkalosis results from an abnormally high pH (above 7.45); a blood pH above 7.8 causes uncontrollable and sustained skeletal muscle contractions. Acids, Bases, and Salts The body contains both inorganic and organic acids and bases that may cause acidosis or alkalosis, respectively. An acid is any solute that dissociates in solution and releases hydrogen ions, thereby lowering the pH. Because a hydrogen atom that loses its electron consists only of a proton, hydrogen ions are often referred to simply as protons, and acids are proton donors. A strong acid dissociates completely in solution, and the reaction occurs essentially in one direction. The stomach produces a powerful acid (hydrochloric acid) to assist in the breakdown of food. A base is a solute that removes hydrogen ions from a solution and thereby acts as a proton acceptor. A strong base dissociates completely in solution. Strong bases have a variety of industrial and household uses. Drain openers (Drano) and lye are two familiar examples. A salt is an ionic compound consisting of a cation (except a hydrogen ion) and an anion (except a hydroxide ion). Because they are held together by ionic bonds, many salts dissociate completely in water, releasing cations and anions. Buffers and pH Control Buffers are compounds that stabilize the pH of a solution by removing hydrogen ions. Buffer systems involve weak acid and its salt. Buffers in body fluids help maintain the pH within normal limits. The use of antacids, such as Alka-Seltzer, provides one illustration of the type of reaction that occurs in buffer systems. Alka-Seltzer neutralizes excess hydrochloric acid in the stomach by using sodium bicarbonate. 5.5 Carbohydrates Carbohydrates are molecules classified as a kind of organic compound. Organic compounds contain the elements carbon, hydrogen, and oxygen. A carbohydrate is an organic molecule that contains carbon, hydrogen, and oxygen in a ratio near 1:2:1. Many organic molecules are made up of long ©2018 Achieve Test Prep Page 53 of 367