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ACID BASE BALANCE BY DR. VENKATA.pptx

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ACID BASE BALANCE BY DR. VENKATA.pptx

  1. 1. DR. VULLI VENKATA RAO Ph.D.(Medical Biochemistry) SENIOR LECTURER DEPARTMENT OF BIOCHEMISTRY ACID BASE BALANCE
  2. 2. Objectives. ■ Concept of Acid & base. ■ pH and H ion concentration. ■ Handerson-Hasselbalch equation. ■ Mechanisms to maintain acid base balance. ■ Applied aspects. Saturday, April 18, 2015
  3. 3. ACIDS ❑ Acids are the substances which can donate H+ ion (proton). ❑These are hydrogen containing substances which can dissociate in soln. to release H+. ❑Not all hydrogen containing substances are acids; e.g. Carbohydrate. H+ HCl + Cl-
  4. 4. ACIDS ❑ Types of acids in the body: 1. Volatile Acids: ➢Can leave the solution and enter the environment. ➢H2CO3 is the only volatile acid in the body. 2. Non-Volatile Acids (Fixed Acids/Metabolic Acids): ➢Acids that do not leave the solution. ➢All other acids in the body. ➢Ex: Pyruvic acid, Lactic acid, Phosphoric acid etc. H2CO3 H2O + CO2
  5. 5. ACIDS ❖ Physiologically important acids: ❖Carbonic acid (H2CO3) ❖Phosphoric acid (H3PO4) ❖Pyruvic acid (C3H4O3) ❖Lactic acid (C3H6O3) ❖ These acids are products of various metabolisms in the body. ❖ Dissolved in body fluids.
  6. 6. BASE ➢ ➢ Bicarbonate (HCO3 -) Biphosphate (HPO4 ) -2 ❑ Base is a substance which can accept H+ ion (proton).,e.g. Hydroxyl ion (OH-). OH- +H+ H2O ■Physiologically important bases:
  7. 7. Alkali ❑ Used synonymously with base. ❑ Molecule formed by combination of an alkaline metal (Na,K,Li) with a highly basic ion. ➢ Ex- NaOH, KOH, NaHPO4 ❑ Base portion of these molecules react quickly with H+to remove these from solution, i.e. alkalis act as typical bases. NaOH + H+ Na+ + OH- H2O
  8. 8. Acids & Bases can be classified as strong or weak acid/base ■ Strong acid/base: ■ One that dissociates completely in a solution. ■ Ex: HCl, H2SO4, NaOH ■ Weak acid/base: ■ One that dissociates partially in a solution. ■ Ex: H2CO3, HCl NaOH H+ + Cl- Na+ + OH- H2CO3 H+ + HCO3-
  9. 9. Weak base: NH3+H2O-----NH4++OH-
  10. 10. pH:potential of hydrogen The letters pH stand for potential of hydrogen, since pH is effectively a measure of the concentration of hydrogen ions (that is, protons) in a substance.
  11. 11. PH SCALE ❑ Normal blood pH is 7.35 - 7.45 ❑ pH range compatible with life is 6.8 - 8.0 pH = - log H+ concentration pH = 7.4 The pH is a measure of the concentration of hydrogen ions, the acidity or alkalinity of a solution. The pH-scale is normally between 0 and 14.
  12. 12. pH SCALE
  13. 13. 29-Nov-22 Acid Base Balance 13 Normal H+ Concentration Because of low H+ conc in body fluids H+ concentration Customarily expressed on logarithm scale Using pH units pH = log (1/[H+]) = -log[H+]
  14. 14. 29-Nov-22 Acid Base Balance 14 Normal H+ Concentration With a normal [H+] = 40 nEq/L = 0.00000004 Eq/L pH = -log[0.00000004] pH = 7.4 Thus pH is inversely related to [H+] Low pH corresponds to high [H+] High pH corresponds to low [H+]
  15. 15. ❑ Normal blood pH is 7.35 - 7.45 ❑ pH range compatible with life is 6.8 - 8.0
  16. 16. PH SCALE pH = - log [H+] pH = log 1/ [H+] ❑ pH is inversely related to H+concentration. low pH – indicates high H+concentration. high pH – indicates low H+concentration. ❑pH = 4 has 10 times more free H+concentration than pH = 5 and 100 times more free H+concentration than pH = 6 ❑pH range from 1-14. pH < 7 – Acidic pH > 7 – Basic pH 7 - Neutral
  17. 17. PH of the ECF is regulated very precisely ACIDOSIS ALKALOSIS NORMAL DEATH DEATH Venous Blood Arterial Blood 7.3 7.4 7.5 6.8 8.0
  18. 18. EFFECTS OF pH change ■ pH changes have dramatic effects on normal cell function ■ 1) Changes in excitability of nerve and muscle cells ■ 2) Influences enzyme activity ■ 3) Influences K+levels 18
  19. 19. Changes in cell excitability ■ pH decrease (more acidic) depresses the central nervous system ■ Can lead to loss of consciousness ■ pH increase (more basic) can cause over-excitability ■ Tingling sensations, nervousness, muscle twitches pH Excitability pH Excitability 19
  20. 20. Influences on enzyme activity ■ pH increases or decreases can alter the shape of the enzyme rendering it non-functional ■ Changes in enzyme structure can result in accelerated or depressed metabolic actions within the cell 20
  21. 21. ACID BASE BALANCE ■ ■ pH maintenance means maintaining [H+]. ■ This involves two important ions which are regulated by various chemical & physiological process: H+ HCO3 -
  22. 22. 29-Nov-22 Acid Base Balance 22 Henderson Hasselbach Equation pH = pKa + log(Base)/(Acid) This is the Henderson-Hasselbach equation
  23. 23. Diagnosing Acid-Base imbalance ■Remember 3 important values: pH = 7.4 pCO2 = 40 mm Hg HCO3- = 24 mmol/l

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