ACID BASE BALANCE and Disorders

1. ACID BASE BALANCE and Disorders

2. Acids : • Are any substance which tends to release H+ in water , either by simple dissociation or reaction • The strength of acids is measured by the extent to which it liberate H+ but not by the number of H+ in the acid molecule e.g. phosph . a. and carbonic a . are weaker than HCL ( the later is completely dissociated ). • The acidity of the solution is determined by H‑ expressed in gm ion/l. ( or nmol/l.).

3. Bases: • Are substances which tends to accept H+, since the anion liberated along with H+ when acid dissociated were bases e.g. Cl in HCL, NH3 in NH+4 • The strong base is that substance with high tendency to accept H+ e.g. anion of weakly dissociated acid e.g H2CO3

4. Aprote: • Metallic cation e.g Na+ , K+ which are not bases or acids

5. HYDROGEION HOMEOSTASIS The buffer : • It is the substance which resists change in its PH, when excess acid or base is added • Usually are weak acids and its salts e.g. H2CO3

6. Addition of acids → dissociation of the weak acid or its salt e.g. H2CO3 ( H+ , HCO3 0 slowely and the anion neutralize any excess acid ( H+) e.g HCL +NaHCO3 → NACl + H2CO3. ( weak acid is formed instead of strong one ). • Addition of bases → dissociation of the weak acid H+ + HCO3 , H+ neutralize the base added without great change in PH.

7. →pH← • It is log10 Log10 of the reciprocal of (H+) • The Log10 of a number is the power to which 10 must be raised to produce this number e.g log10 102 = if log10 to "x" number = 7 so the number must be 107 • At pH6 (H+) =?? 1 H+

8. 1 H+ pH = Log10 Log10 (H+) = 6 ( H+) 10-6 = 0.000001 mol = 1000nmol/L at pH7 , (H+) will be 100 nmol/L so each one unit change in pH mean 10 folds change in (H+)

9. Blood Buffer systems • Bicarbonate / Carbonic acid • The most important buffer of plasma • It presents in RBCs , but in lesser concentration

10. HANDERSON – HASSELBALCH equation dissoeiation hydration CO2 + H2O H2CO3 H++ HCO3 K hydration = H2CO3 → H+ + HCO3 H2CO3 CO2xH2O

11. H+ x HCO3 H2CO3 K dissociation = K combined = x = H2O is constant and so K → K` H2CO3 CO2xH2O H+ xHCO3 H2CO3 H+ x HCO3 CO2xH2O

12. H+ x HCO`3 dCO2 K` = ( H+) = K` x pH = Log10 = Log + log = pK + Log dCO2 HCO`3 1 (H+) 1 K HCO`3 dCO2 HCO`3 0.03xPCO2

13. Note : ( dissociation constant of CO2 = 0.03) ( PK. For BiC. / Carb. Buffer system = 6.1)

14. 2) Phosphate buffer :- • Inorganic phosphate accounts for 5% of the nonbicarbonate buffer value, at a plasma Ph of 7.4 , the ratio HPO4/H2PO4 is 80/20 ( 4/1) (PK=6.8)

15. Organic phosphate in the RBCs in the form pf 2.3-diphosphoglycerate accounts for 16% of the non bicarbonate buffer. H2PO4+OH= HPO`4 + H2O HpO`4 + H= = H2Po4

16. Plasma protein buffer:-3) • Albumin form 95% of the non bicarbonate buffer value of the plasma • The most important buffer groups of proteins are the imidazole group of histidine ( 16 in each albumin molecule)

17. Hemoglobin buffer : • Account for 84% of the RBCs non bic buffer the most important buffer groups are imidazole groups of Hb. Histidine

18. Carbamino Compoands : Combination of small amount of CO2 in RBCs with Hb.R – NH2 + Co2 R – NH – COO + H+

19. Regulation of (H+) • Dilution • Buffer system → Plasma • HCO3/H2CO3 (20:1) • B2HPO4 / BH2PO4 ( 4:1) • Prot. /prot.H(95% of the non bic

20. RBCs : • HbO2 / HHb ( 84% of the non bicarb.) • Carbamino compounds • HCO3 /H2CO3 ( to less extent) • 2.3 diph. glye.16%of the non bic.

21. 3 . Respiratory Mechanism = C.R.C. ( Central chem.., Periph. Chem.) 4 . Renal Mechanism • Acid excrction • Na+ -H+ exchange • Ammonia formation and NH+4 excretion • H2PO4 excretion • HCO`3 reclamation