<prompt> Most abundant buffer in blood is:ProteinHemoglobinBicarbonatesAll of the above  <response>: The primary buffers in blood are bicarbonate, imidazole histidine amino acid groups on hemoglobin, albumin, and globulin, and phosphate. Bicarbonates contribute to 50 of the total buffers of blood. The pH of blood is 7.35 - 7.45. Buffer system in blood is Carbonic acid-bicarbonate Phosphates Plasma proteins--are effective buffers because both their free carboxyl and their free amino groups dissociate. Dissociation of the imidazole groups of the histidine residues in hemoglobin. Carbonate buffer: Is the most impoant buffering system of blood. H2CO3 H2O - H3O HCO3-. Excess acid H3O in the body is neutralized by HCO3- H2CO3 H2O - H3O HCO3- Equilibrium shifts left Excess base OH- reacts with the carbonic acid H2CO3 H2CO3 OH- - H2O HCO3- Equilibrium shifts right Impoance: H2CO3 dissociates into CO2 and H2O, allowing H3O to be eliminated as CO2 by the lungs Changes in PCO2 modify the ventilation rate. HCO3- concentration can be altered by kidneys. Phosphate: The phosphate buffer system HPO42-H2PO4- plays a role in plasma and erythrocytes. H2PO4- H2O - H3O HPO42- Any acid reacts with monohydrogen phosphate to form dihydrogen phosphate dihydrogen phosphate monohydrogen phosphate H2PO4- H2O - HPO42- H3O The base is neutralized by dihydrogen phosphate dihydrogen phosphate monohydrogen phosphate H2PO4- OH- - HPO42- H3O Protein: Proteins contain - COO- groups, which, like acetate ions CH3COO-, can act as proton acceptors. Proteins also contain - NH3 groups, which, like ammonium ions NH4, can donate protons. If acid comes into blood, hydronium ions can be neutralized by the - COO- groups - COO- H3O - - COOH H2O If base is added, it can be neutralized by the - NH3 groups - NH3 OH- - - NH2 H2O Regulation of blood pH: The lungs and kidneys play impoant role in regulating blood pH. The lungs regulate pH through retention or elimination of CO2 by changing the rate and volume of ventilation. The kidneys regulate pH by excreting acid, primarily in the ammonium ion NH4, and by reclaiming HCO3- from the glomerular filtrate and adding it back to the blood. Whole blood buffering system Blood Contribution to buffering of fixed acid load Bicarbonate Plasma Red blood cells 35 18 Non Bicarbonate buffers Hemoglobin Plasma proteins Organic phosphorus Inorganic phosphorus 35 7 3 2 Ref: Marks essential medical biochemistry, By Lieberman, Allan D. Marks,Page 31. 