Most abundant buffer in blood is:
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.
Protein
Hemoglobin
Bicarbonates
All of the above