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BIOCHEMISTRY CHEMISTRY OF LIFE

BIOCHEMISTRY CHEMISTRY OF LIFE. BUFFERS. MAINTANENCE OF NORMAL PH. There are three natural systems in our body which regulate and maintain the normal PH and also provide defense against change in the PH of the body. 1 . Acid base Buffer System (Chemical) 2 . Respiratory System

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BIOCHEMISTRY CHEMISTRY OF LIFE

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  1. BIOCHEMISTRYCHEMISTRY OF LIFE

  2. BUFFERS

  3. MAINTANENCE OF NORMAL PH • There are three natural systems in our body which regulate and maintain the normal PH and also provide defense against change in the PH of the body. 1 . Acid base Buffer System (Chemical) 2 . Respiratory System 3. Renal System

  4. 1. Chemical Buffer Systems ~ 1st to respond ~ Take < 1 sec. ~ Temporarily “tie up” excess acids & bases THREE TYPES OF BUFFER mainly 1.Carbonic acid – Bicarbonate buffer 2.Phosphate buffer 3.Protein buffer

  5. 2. Respiratory Mechanism ~ 2nd to respond ~ Takes 1-3 minutes ~ Respiratory centre involved ~ Removes CO2 & therefore H2CO3 3. Renal Mechanism ~ 3rd to respond but most potent ~ Takes hours to days ~ Kidneys remove metabolic acids Eg phosphoric, uric & lactic acids; ketone bodies

  6. 1-Chemical Buffer Systems • A buffer solution is a solution that resists any change in its PH when a small amountof acid or a base is added to it.

  7. Composition of buffer • Abuffer solution consists of weakly dissociated acid (proton donor) and its conjugate salt of strong base (proton acceptor) or a weak base and its conjugated strong salt.

  8. General Components A buffer contains: ~ a weak acid & its strong salt or ~ a weak base & its strong salt NSC1951 Lecture 19: Buffers

  9. Effect of acid and base on water Effect of acids and base on buffer solution NSC1951 Lecture 19: Buffers

  10. 1-Chemical Buffer Systems 1. Extra cellular fluid buffers are: • Bicarbonate buffer • Protein buffer (Hb, plasma protein, amino acids). 2. Intercellular buffer are: • Phosphate buffer • Protein buffer (Hb, plasma protein, amino acids). The strength of a buffers solution is given as molar.

  11. ECF BUFFERS Bicarbonate Buffer System (Carbonic Acid ) ~ Most important in the ECF Pka : 6.1

  12. Bicarbonate Buffer System (Carbonic Acid ) • The plasma bicarbonate(HCO3-) con is 24mmol/l. • Carbonic acid con( product of PCO2 and solubility constant of CO2(40X0.03 )1.2mmol/l). • At PH 7.4 the bicarbonate to carbonic acid ratio is 20:1. • PH = pka +log (base) (acid)

  13. BicarbonateBufferSystem • It consist typically a mixture of H2CO3 and NaHCO3. • When a strong acid is added : HCI + NaHCO3 ……….> H2CO3 + NaCI . When a strong base is added : NaOH + H2CO3 …………> NaHCO3 + H2O. . Bicarbonate buffer system is the chief buffer system of plasma against fixed acids . pKa = 6.1 (equalibrium or dissociation constant ) . Serum level = 24 mmol/L . Buffer equation : PH = pKa + Iog HCO3-/ CO2

  14. NSC1951 Lecture 19: Buffers

  15. NSC1951 Lecture 19: Buffers

  16. Phosphate Buffer system ~ Important in ICF & urine Pka 6.8

  17. Phosphate Buffer system • At PH 7.4 the sodium dihydrogen phosphate and disodium hydrogen phosphate (NaH2PO4-Na2HPO4) ratio is 4:1. • Present in low concentration but due to its pka value 6.8 it is very effective.

  18. PHOSPHATE BUFFER SYSTEM Typically of a mixture of Na2HPO4 (salt ) and NaH2PO4 (salt ) . pKa = 6.8 (equalibrium or dissociation constant ) . When a strong acid is added : HCI + NaH2PO4 ………> NaH2PO4 + NaCI . When a strong base is added : NaOH + NaH2PO4 ……..> NaHPO4 + H2O Buffer equation PH= pKa + log HPO4-/H2PO4-

  19. Protein Buffer Systems ~ Important in ECF and ICF ~ Interact with other buffer systems

  20. Protein Buffer Systems • 1.plasma protein buffer • 2. amino acid buffer • 3. hemoglobin buffer system. The buffering capacity of of protein system of the blood dependent on the pk of the ionizable group of amino acids The imadazole group of histadine pk=6.7 is the most effective of protein buffers. The plasma buffers account for 2% of total buffering capacity of the plasma.

  21. Protein Buffer Systems • Hb Buffer system ~ RBC only ICF ~ Helps prevent   pH when   PCO2

  22. Amino Acid Buffers (all proteins) • Plasma Protein Buffers ~ Slower than other chemical buffers ~ Remove either excess H+ or excess OH- depending on pH

  23. PROTEINBUFFERSYSTEM • It consist of intracellular and plasma proteins • pKa = 7.4 • When strong acid is added : Amino acid accepts excess of H+ ions to increase PH to normal . When strong base is added : Amino acid release H+ ions to decrease PH to normal . Buffer equation = PH = pKa + log protein-/H. protein .

  24. R  NH2 – C – COO- + H+  H • If  pH (more basic)  [OH- ] Amino acid acts like an acid • If  pH (more acidic)  [H+] Amino acid acts like a base R  NH3+– C – COOH  H

  25. Hb Hemoglobin erythrocyte CO2+H2O CA H2CO3 HHb HCO3 + H Hb CI • Plasma Lungs CO2 HCO3- HHb+o2 CI- H+ HCO3- HbO2

  26. IMPORTANCE • Buffers are the 1st line defence against strong acids or base which might get entry into the living body. • Any condition that change the balance of any one of Buffer system also changes the balance of others . This phenomenon is called isohydric principle.

  27. 2.Respiratory mechanism of buffering 2CO2+H2O Exhaled Carbonic anhydrase 2H2CO3 2CO2+H2O Hb4O2 2HCO3- 2H+ H2CO3- 4O2 2H+ 2HCO3- 4O2 Periphral tissues Hb2H Lungs

  28. 3-Renal buffering mechanism Blood renal cell tubular lumen Na+ Na+ Na+ HCO3- HCO3- H+ H+ B- H2CO3 HB carbonic anhydrase CO2 + H2O Excreted

  29. 1. REGULATION OF ACID-BASE BALANCE BLOOD NORMAL PH: Homeostatic range for blood pH 7.35 – 7.45  or  can be fatal • pH < 7.35 Acidosis • pH > 7.45 Alkalosis

  30. ACIDOSIS:A pathochemical condition accompanied by lowering of blood PH below 7.36. • RESPIRATORY ACIDOSIS • METABOLIC ACIDOSIS NSC1951 Lecture 19: Buffers

  31. Respiratory Acidosis Of respiratory origin ~ Shallow breathing ~  CO2 exhaled  CO2 retained  CO2 H+pH <7.35 CAUSES: 1.Lung diseases blocking gas diffusion eg pneumonia, emphysema 2 .Defects of higher respiratory centre. 3 .Defects of thoracic cage . 4 .Defect in gaseous exchange. Treatment : .a. Artificial respiration. b. Drugs. NSC1951 Lecture 19: Buffers

  32. Metabolic Acidosis loss of base or retention of acids. filtration of large no of HCO3- ions so renal buffer system activated H+ ion are secreted to remove acid from the body. H+ pH < 7.35 causes : 1 .Excessive loss of HCO3. 2 .Ureamic acidosis. 3 .Excessive production of non-volatile acids. 4.Renal diseases 5. Diarrhoea 6.Starvation Treatment ; administrationof. • Sodium bicarbonate. • Sodium lactate. c. Sodium gluconate. NSC1951 Lecture 19: Buffers

  33. ALKALOSIS:A pathochimical condition accompanied by raising of blood PH above 7.4 • RESPIRATORY ALKLOSIS • METABOLIC ALKALOSIS NSC1951 Lecture 19: Buffers

  34. Respiratory Alkalosis Of respiratory origin CO2 exhaled Hyperventilation  CO2  H+pH > 7.45 CAUSES:. Anxiety , hysteria ,tension ,pain, hypoxia , CNS injury etc

  35. Metabolic Alkalosis Alkalosis due to loss of metabolic or fixed or non-volatile acids or due to retention of bases HCO3- ions and Na+ ions are excreted in urine to balance the PH. H+pH > 7.45 • CAUSES 1.Excessive loss of H+ ions; 2.Excessive ingestion of Alkaline drugs; 3.Administration of diuretics 4. Ingestion Bicarbonate of Soda (NaHCO3) • TREATMENT Administration or ingestion of • 1; Ammonium chloride • 2; Lysine Monohydrochloride

  36. Buffers consist of Weak acid and its salt Weak base and its salt or and resist changes in pH to Maintain pH balance preventing Acidosis and Alkalosis

  37. BUFFERSOFPLASMA • Plasma has three buffer systems 1 .Bicarbonate Buffer system 2 .Phosphate Buffer system 3 .Protein Buffer system

  38. BUFFERSOFRBC • In erythrocytes also three different buffering system function. 1. Bicarbonate – carbonic acid. 2. Oxyhaemoglobinate – Oxyheamoglobin 3. Heamoglobinate - Heamoglobin.

  39. BUFFERSOFTISSUES • BUFFERING SYSTEM OF LYMPH. • BUFFERING SYSTEM OF SPINAL FLUID.

  40. MAINTENCEOFBLOODPH • The PH of blood is 7.4. • The chief buffer of the blood which maintains the PH is HCO3 / H2CO3. • The ratio HCO3 / H2CO3 is 20 : 1. • PH = pka + log ( salt ) / ( acid ) . • pka of H2CO3 is 6.1. • Salt is HCO3 . • Acid is H2CO3. • Ratio is 20:1. • PH = 6.1 + log 20 / 1. = 6.1 + 1.3 – negligible. = 7.4.

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