ACID BASE BALANCE and Disorders

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.).

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

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

HYDROGEION HOMEOSTASIS The buffer : 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

 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.

→ pH ←  It is log 10 Log 10 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 log = if log10 to "x" number = 7 so the number must be 107  At pH6 (H+) =?? 1H+ 1H+

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

Blood Buffer systems 1) Bicarbonate / Carbonic acid  The most important buffer of plasma  It presents in RBCs, but in lesser concentration

HANDERSON – HASSELBALCH equation CO 2 + H 2 O H 2 CO 3 H + + HCO 3 H + + HCO 3 K hydration = H 2 CO 3 → H + + HCO 3 H2CO3 CO2xH2O hydration dissoeiation

K dissociation = K combined = x = H 2 O is constant and so K → K` H + x HCO 3 H 2 CO 3 CO2xH2O H+ xHCO3 H2CO3 H+ x HCO3 CO2xH2O

K` = ( H+) = K` x pH = Log 10 = Log + log = pK + Log H + x HCO` 3 dCO 2 HCO` 3 1 (H+) 1K1K HCO`3 dCO2 HCO`3 0.03xPCO2

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

 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) 2) Phosphate buffer :-

 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

 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) Plasma protein buffer:- 3)

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

Carbamino Compoands : Combination of small amount of CO 2 in RBCs with Hb.R – NH 2 + Co 2 R – NH – COO + H+

1. Dilution 2. Buffer system → Plasma a. HCO3/H2CO3 (20:1) b. B2HPO4 / BH2PO4 ( 4:1) c. Prot. /prot.H(95% of the non bic Regulation of (H + )

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

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