Acid-Base Balance PDF

Acid-base balance Zoo-103, Unit-II & Zoo-304 (Allied Elective-CBCS) By Dr. S.S. Nishank, Dept. of Zoology, Utkal University by SS Nishank, Dept. of Zoology, Utkal 1 Un...

Acid-base balance Zoo-103, Unit-II & Zoo-304 (Allied Elective-CBCS) By Dr. S.S. Nishank, Dept. of Zoology, Utkal University by SS Nishank, Dept. of Zoology, Utkal 1 University acid-base balance ? Refers to the precise regulation of free (that is unbound) hydrogen ion (H+) concentration in the body fluids. by SS Nishank, Dept. of Zoology, Utkal 2 University  Body fluids consist of water and solutes in three main compartments The major fluid compartments of the body. [Values are for a 70-kg (154-lb) male.] by SS Nishank, Dept. of Zoology, Utkal 3 University by SS Nishank, Dept. of Zoology, Utkal 4 University  Homeostasis of body regulated by Regulation of water intake & output Regulation of Na+, K+, Ca2+ Regulation of pH (acid-base balance regulation) by SS Nishank, Dept. of Zoology, Utkal 5 University Why acid base balance is important? Changes in excitability of nerve & muscle cells Influence on enzyme activity Influence on K+ levels in body (e.g. acidosis causes decreased K+ secretion whereas alkalosis causes increased K+ secretion) by SS Nishank, Dept. of Zoology, Utkal 6 University Sources of H+ ion in body Carbonic acid formation by metabolic process Inorganic acids produced during breakdown of nutrients Organic acids from intermediary metabolism by SS Nishank, Dept. of Zoology, Utkal 7 University by SS Nishank, Dept. of Zoology, Utkal 8 University by SS Nishank, Dept. of Zoology, Utkal 9 University Where / conjugate base (Ka), which is also called the ionization constant or acid dissociation constant, is given by the expression by SS Nishank, Dept. of Zoology, Utkal 10 University  Henderson-Hasselbalch equation pH of a solution containing an acid or base can be calculated by Henderson-Hasselbalch equation. The Henderson-Hasselbalch equation is used to calculate the pH of a buffered solution. This equation is derived from the behavior of weak acids (and bases) in solution, which is described by the kinetics of reversible reactions: by SS Nishank, Dept. of Zoology, Utkal 11 University by SS Nishank, Dept. of Zoology, Utkal 12 University Thus the final form of the Henderson-Hasselbalch equation is as follows: by SS Nishank, Dept. of Zoology, Utkal 13 University A strong acid has a high Ka and a low pKa. A weak acid has a low Ka and a high pKa. (Henderson-Hasselbalch equation) by SS Nishank, Dept. of Zoology, Utkal 14 University Buffer ? A buffer is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid by SS Nishank, Dept. of Zoology, Utkal 15 University by SS Nishank, Dept. of Zoology, Utkal 16 University  Buffering capacity ? In most cases, pH buffering is effective when the solution pH is within ±1 pH unit of the buffer pKa. by SS Nishank, Dept. of Zoology, Utkal 17 University by SS Nishank, Dept. of Zoology, Utkal 18 University by SS Nishank, Dept. of Zoology, Utkal 19 University  TRIS buffer is often toxic to biological systems: because of its high lipid solubility it can penetrate membranes, uncoupling electron transport reactions in whole cells and isolated organelles. In addition, it is markedly affected by temperature, with a tenfold increase in H+ concentration from 4 °C to 37 °C. by SS Nishank, Dept. of Zoology, Utkal 20 University Application of Henderson- Hesselbalch equation by SS Nishank, Dept. of Zoology, Utkal 21 University Solution of Q.1 by SS Nishank, Dept. of Zoology, Utkal 22 University  Solution Q.2 The calculated pH equals the pK of the buffer. This important calculation demonstrates that when the pH of a solution equals the pK, the concentrations of the acid and base forms of the buffer are equal. A buffer functions best when the pH of the solution is equal (or nearly equal) to the pK of the buffer, precisely because the concentrations of the acid and base forms are equal or nearly equal. by SS Nishank, Dept. of Zoology, Utkal 23 University by SS Nishank, Dept. of Zoology, Utkal 24 University  Going from right to left, as strong acid is added, H+ combines with the basic form of phosphate: Going from left to right, as strong base is added, OH− combines with H+ released from the acid form of the phosphate buffer: by SS Nishank, Dept. of Zoology, Utkal 25 University by SS Nishank, Dept. of Zoology, Utkal 26 University pH is regulated by by SS Nishank, Dept. of Zoology, Utkal 27 University by SS Nishank, Dept. of Zoology, Utkal 28 University by SS Nishank, Dept. of Zoology, Utkal 29 University  Regulation of pH by buffers The bicarbonate buffer system is a mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate (NaHCO3, a weak base), in the same solution When a strong acid such as HCl is added to this buffer system When a strong base such as sodium hydroxide (NaOH) is added by SS Nishank, Dept. of Zoology, Utkal 30 University  Regulation of pH by buffers Phosphate Buffer System by SS Nishank, Dept. of Zoology, Utkal 31 University Regulation of pH by buffers by SS Nishank, Dept. of Zoology, Utkal 32 University by SS Nishank, Dept. of Zoology, Utkal 33 University by SS Nishank, Dept. of Zoology, Utkal 34 University by SS Nishank, Dept. of Zoology, Utkal 35 University  pH regulation by respiration a rising plasma H+ concentration resulting from any metabolic process excites the respiratory center indirectly (via peripheral chemoreceptors) to stimulate deeper, more rapid respiration. As ventilation increases, more CO2 is removed from the blood, pushing the reaction to the left and reducing the H+ concentration. When blood pH rises, the respiratory center is depressed. As respiratory rate drops and respiration becomes shallower, CO2 accumulates, pushing the equilibrium to the right and causing the H+ concentration to increase. by SS Nishank, Dept. of Zoology, Utkal 36 University by SS Nishank, Dept. of Zoology, Utkal 37 University Renal mechanism of acid-base balance by SS Nishank, Dept. of Zoology, Utkal 38 University by SS Nishank, Dept. of Zoology, Utkal 39 University Renal mechanism for regulation of acid base balance by 1. Conservation/ reabsorption of HCO3- 2. Generation of new HCO3- via (a) excretion of buffered H+ / excretion of H+ as titratable acid and (b) NH4+ excretion 3. Excretion of HCO3- by SS Nishank, Dept. of Zoology, Utkal 40 University The rate of H+ secretion rises and falls with CO2 levels in the ECF. The more CO2 in the peritubular capillary blood, the faster the rate of H+ secretion. Because blood CO2 levels directly relate to blood pH, this system can respond to both rising and falling H+ concentrations. by SS Nishank, Dept. of Zoology, Utkal 41 University by SS Nishank, Dept. of Zoology, Utkal 42 University bicarbonate reabsorption & H+ ion secretion in distal tubule by SS Nishank, Dept. of Zoology, Utkal 43 University  Occurs primarily in α-intercalated cells of late Distal tubule & collecting duct Generation of new HCO3- via by SS Nishank, Dept. excretion of Zoology, Utkal of buffered H+ 44 University by SS Nishank, Dept. of Zoology, Utkal 45 University  Generation of new HCO3- via NH4+ excretion by SS Nishank, Dept. of Zoology, Utkal 46 University by SS Nishank, Dept. of Zoology, Utkal 47 University by SS Nishank, Dept. of Zoology, Utkal 48 University bicarbonate secretion & H+ ion reabsorption in distal tubule by SS Nishank, Dept. of Zoology, Utkal 49 University by SS Nishank, Dept. of Zoology, Utkal 50 University by SS Nishank, Dept. of Zoology, Utkal 51 University When respiratory function is normal, theDept. by SS Nishank, PCO2 fluctuates of Zoology, Utkal between 35 and 45 52 mm Hg. University  Bicarbonate ion levels below or above the normal range of 22–26 mEq/L indicate a metabolic acid-base imbalance. The second most common cause of acid-base imbalance, metabolic acidosis, is recognized by low blood pH and HCO3− levels. by SS Nishank, Dept. of Zoology, Utkal 53 University by SS Nishank, Dept. of Zoology, Utkal 54 University by SS Nishank, Dept. of Zoology, Utkal 55 University by SS Nishank, Dept. of Zoology, Utkal 56 University by SS Nishank, Dept. of Zoology, Utkal 57 University by SS Nishank, Dept. of Zoology, Utkal 58 University by SS Nishank, Dept. of Zoology, Utkal 59 University Factors influencing increased H+ secretion by kidney tubule epithelium by SS Nishank, Dept. of Zoology, Utkal 60 University by SS Nishank, Dept. of Zoology, Utkal University 61 Intracellular pH regulation by SS Nishank, Dept. of Zoology, Utkal 62 University by SS Nishank, Dept. of Zoology, Utkal 63 University by SS Nishank, Dept. of Zoology, Utkal 64 University Intra cellular acid-base balance by SS Nishank, Dept. of Zoology, Utkal 65 University by SS Nishank, Dept. of Zoology, Utkal 66 University Response of cell to respiratory acidosis by SS Nishank, Dept. of Zoology, Utkal 67 University Respiratory & renal compensation by SS Nishank, Dept. of Zoology, Utkal 68 University