endocrine and metabolic disorders
Acid Base Regulation
Acid Base Physiology
Most acidcomes from metabolism of Carbohydrates Fats Metabolism of carbohydrates and fats generates 15,000 to 20,000 mmol of carbon dioxide (CO2) daily. CO2is not an acid itself, but in the presence of a member of the carbonic anhydrase family of enzymes, CO2combines with water (H2O) in the blood to create carbonic acid (H2CO3), which dissociates into hydrogen ion (H+) and bicarbonate (HCO3−). The H+binds with hemoglobin in red blood cells and is released with oxygenation in the alveoli, at which time the reaction is reversed by another form of carbonic anhydrase, creating water (H2O), which is excreted by the kidneys, and CO2, which is exhaled in each breath. Lesser amounts of organic acidderive from the following: Incomplete metabolism of glucose and fatty acids into lactic acid and ketoacids Metabolism of sulfur-containing amino acids (cysteine, methionine) into sulfuric acid Metabolism of cationic amino acids (arginine, lysine) Hydrolysis of dietary phosphate This “fixed” or “metabolic” acid load cannot be exhaled and therefore must be neutralized or excreted by the kidneys. Most basecomes from Metabolism of anionic amino acids (glutamate, aspartate) Oxidation and consumption of organic anions such as lactate and citrate, which produce HCO3− 