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pH of Body Fluids I. A. Remember that to an extent water ionizes to form protons (H+) and proton acceptors (OH-) H 2O 1. H+ + OH- The pH of a solution is determined by the measure of the solutionβs H+ ion concentration. a. When a solution is acidic it has a higher H+ concentration than OH- concentration b. When a solution is basic it has a higher concentration of OH- concentration than H+ concentration 2. In our bodies, many different changes, both internal and external, effect pH. Controlling pH in our Bodies II. A. 1. 2. The pH of the blood needs to be within a narrow pH range of 7.35-7.45. There are three ways that the blood pH is maintained: the buffer system, the respiratory system, and the urinary system. The pH of blood differs in arteries and veins: because of (carbon dioxide) CO2 level differences and filtering in the kidneys. The blood in veins is slightly more acidic because of a chemical reaction that occurs between CO2 and water (H2O). B. 1. CO2 is released into the veins from all of the cells undergoing cellular respiration around the blood capillaries. a. CO2 (from cellular respiration) will combine with water in the veins (from plasma) to produce carbonic acid (H2CO3). π―π πΆ + πͺπΆπ ππππππππ πππππ ππππβ πππππ *Carbonic anhydrase is an enzyme necessary to speed up the rate of this reaction. b. H2CO3 will then travel in venous blood back to the lungs where the reverse reaction takes place. π―π πͺπΆπ ππππππππ πππππ ππππ π―π πΆ + πͺπΆπ π―π πΆ + πͺπΆπ ππππππππ πππππ ππππ π―π πͺπΆπ 2. If you hold your breath the amount of carbonic acid in the blood will decrease the pH of the blood. Acidosis β condition in which there is an excessive proportion of acid in the blood Alkalosis β condition in which there is an excessive proportion of alkali (base) in the blood C. Buffers in the blood work to make sure the pH remains at homeostasis. Buffer β compound that combines with an acid or with a base to form a weaker acid or base, thereby lessening the change in hydrogen-ion concentration that would occur without the buffer 1. The strength of an acid depends on the amount of H+ ions in the solution. The higher the concentration of H+ ions, the stronger the acid. The strength of a base depends on the amount of *OH- ions in the solution. The higher the concentration of OH- ions in the solution, the stronger the base. *Or any proton-accepting compound 2. Sodium bicarbonate (NaHCO3) buffers extreme acids by buffering the strong acid (i.e. Hydrochloric acid, HCl) to make a much weaker acid and sodium chloride. Carbonic acid buffers extreme bases by buffering the strong base (i.e. Sodium hydroxide, NaOH) to make NaHCO3 and water. Sodium bicarbonate buffers weak acids by buffering the weak acid to form a weaker acid and sodium lactate. D. 1. 2. The kidneys are the most efficient organs for regulating blood pH because they can remove both excess acids and excess base. Kidneys usually acidify urine to a pH of approximately 4.8. The kidneys conserve sodium bicarbonate (NaHCO3) in 2 ways. (While still excreting acid) III. pH Imbalances In humans the acid-base balance needs to be maintained at the proper ratio of 20 NaHCO3 to 1 H2CO3. A. 1. 2. CO2 is expelled in the respiratory and urinary systems so that the levels of H2CO3 can drop, raising the pH of the blood to normal levels. Proteins that contain an βNH2 group are expelled in the urinary system so that protons from the NH2 will not raise the acid (lower pH) level of the blood. Metabolic disturbances in acid-base balance result in metabolic acidosis and metabolic alkalosis. B. 1. 2. Metabolic acidosis can be caused by a bicarbonate deficiency caused by renal failure/disease, uncontrolled diabetes, prolonged diarrhea, or the ingestion of toxic chemicals like antifreeze (ethylene glycol) or wood alcohol (methanol). Metabolic alkalosis can be caused by bicarbonate excess. This can be the result of diuretic therapy, loss of gastric juice due to vomiting or suction or from certain diseases. Respiratory disturbance C. 1. 2. Respiratory acidosis can be caused by an excess of H2CO3 resulting from slow breathing that will increase the concentration of CO2 in the arteries. This can happen due to depressed breathing due to anesthesia, drugs, or pulmonary disease. Respiratory alkalosis can be caused by an H2CO3 deficit resulting from excessive loss of CO2 due to hyperventilating. Hyperventilation can occur due to nervousness, overinflation of patients on ventilators, or a hepatic coma. a. 1. 2. 3. 4. The removal of CO2 occurs when: CO2 leaves the blood and enters the distal tubules of the kidneys In the kidneys it reacts with H2O to form H2CO3 A proton leaves H2CO3 and enters the urine leaving HCO3- to bind with a Na+ ion to form NaHCO3 The H+-ion makes a weak acid (NaH2PO4) and is excreted with urine. b. 1. The removal of amino groups (-NH2) when: Breaking down proteins result in the release of amino acids into blood. 2. -NH2 leaves the blood and enters the distal tubules of the kidneys 3. A proton joins βNH2 to form NH3. NH3 then goes into urine. 4. In urine, NaCl dissociates and a Cl- ion joins NH3 to make NH3Cl- (a base) 5. H2CO3 releases a H+ ion that enters the urine to join NH3Cl- to form NH4Cl to be excreted with the urine 6. HCO3 in the kidneys bonds with Na+ to make NaHCO3