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Buffer Systems

Buffer Systems. Introduction. Acid-base regulation Regulation of hydrogen ion Buffer system Respiratory regulation Renal regulation. Why To Regulate. To maintain homeostasis Regulates enzymatic functions. Acids And Bases. Acids Release protons (H) ; Eg -H 2 CO 3 , HCL Bases

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Buffer Systems

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  1. Buffer Systems

  2. Introduction • Acid-base regulation • Regulation of hydrogen ion • Buffer system • Respiratory regulation • Renal regulation

  3. Why To Regulate • To maintain homeostasis • Regulates enzymatic functions

  4. Acids And Bases • Acids • Release protons (H) ;Eg-H2CO3 , HCL • Bases • Accept protons (H) ; Eg-HCO3

  5. Types of acids and bases • Strong acids • Release large amount of Hydrogen ions • Weak acids • Release small amount of Hydrogen ions • Strong bases • Accept large amount of Hydrogen ions • Weak bases • Accept small amount of Hydrogen ions

  6. Hydrogen ion conc. Determines pH

  7. What Is Buffer ??? • A buffer is a solution (or a substance) that has the ability to maintain pH and bring it back to its optimal value by addition or removal of hydrogen ions Buffer + H H buffer

  8. Contd…. • When Hydrogen ion conc. Increases • Reaction shifts towards right • When Hydrogen ion conc. Decreases • Reaction shifts towards left In this way hydrogen ion concentration is maintained

  9. Types of chemical buffer • Carbonic acid-bicarbonate – • Buffering changes caused by organic and fixed acids • Protein buffer system-Amino acids • Minor buffering system- • Phosphate –Buffer pH in the ICF

  10. Figure 27.7

  11. Carbonic Acid-Bicarbonate Buffering System • Carbonic acid-bicarbonate buffer system • Weak acid – H2CO3 • Bicarbonate salt (NaHCO3) • Strong acid is added • When HCL is addedHydrogen conc. increases • CO2 + H2O H2CO3  H + HCO3

  12. Contd… • Strong base is added • H+ conc. Reduces NaOH + H2CO3 NaHCO3+H2O In this way CO2conc. decreases This inhibits respiration.

  13. Bicarbonate buffer- • Has the following limitations: • Cannot protect the ECF from pH changes due to increased or depressed CO2 levels • Only functions when respiratory system and control centers are working normally • It is limited by availability of bicarbonate ions (bicarbonate reserve).

  14. Phosphate buffer system- • Main elements of phosphate buffer system- - H2PO4, and HPO4 • Phosphoric acid changes pretty quickly into dihydrogenphosphate, or H2PO4-.   • This dihydrogen phosphate is an efficient buffer.

  15. Contd…

  16. Contd…. • Phosphate buffer system in the ECF is low compared to the bicarbonate buffer. • Its buffering power is less compared to the bicarbonate buffer. • It has its importance in the renal tubules of kidneys for two reasons. .

  17. Contd • 1.Conc. of phosphate is more in tubules. • 2. Tubular fluid has lower pH. • Conc. of phosphate is more in ICF compared to ECF.

  18. Protein buffer system • Proteins are made up of amino acids • Amino acids have a central carbon with four groups off of it: 1.a carboxyl group (COOH) 2.an amino group (NH2) 3.a hydrogen atom 4.an R group .

  19. Structure of amino acids

  20. Contd… • The carboxyl and amino groups are what enable proteins to act as buffers. • Carboxyl group is attached to the amino acid central carbon:   C - COOH • Carboxyl group consists of a double bond to one of the oxygens and a single bond to the hydroxyl group. 

  21. Contd... • At neutral pH the carboxyl ion is present as COO instead of COOH. • Acidic medium – becomes COOH • Basic medium – becomes COO.

  22. Contd… • Amino groupis attached to the amino acid central carbon:  C - NH2. • Neutral pH, the amino group is actually- NH3+ rather than just NH2. • Acidic medium – becomes NH3+ • Basic medium- becomes NH2

  23. Contd..

  24. Respiratory regulation When alveolar ventilation increases CO2 conc. In ECF decreases H+ conc. decreases Or vice versa.......

  25. Respiratory regulation Contd… • Pulmonary expiration of CO2 balances metabolic formation of CO2 • 1.2 mol/L of dissolved CO2is present in the ECF corresponding to pCO2of 40 mm/hg • Rate of pulmonary ventilation is inversely proportional toCO2 & pCO2 • So either pulmonary ventilation rate of CO2 • or its formation by tissues can change pCO2 in ECF.

  26. Contd… • Increasing alveolar ventilation decreases ECF hydrogen ion conc. And raises pH • If alveolar ventilation increases the pCO2 decreases. • If alveolar ventilation decreases the pCO2 increases. • Twice rise of AV--rises pH of ECF by about 0.23 • Decrease of AV to ¼ -- decreases pH by 0.45

  27. Contd… • Increased Hydrogen ion conc. Stimulates alveolar ventilation • Change in alveolar ventilation rate is much greater in reduced levels of pH than in increased levels of pH

  28. Reason Alveolar ventilation rate decreases Increases pH O2 added in blood reduces Demand of O2 in blood increases pO2 also decreases Stimulates ventilation

  29. Feedback control of Hydrogen ion conc. By RS H conc. Falls below normal Respiration is depressed Alveolar ventilation decreases H increases back to normal

  30. Bufffering power of RS • The kidneys work in elimination of hydrogen ion conc. and control imbalance. • Its capacity is 1-2 times as much as other chemical buffers.

  31. Impairment of lungs function: • Impairment of lung function leads to emphysema and respiratory disorders. • Kidneys play a major physiologic mechanism for returning pH to normal

  32. Renal mechanism of acid-base regulation • Kidneys regulate the blood pH by • 1. maintaining alkali reserves • 2. excreting / reabsorbing acid/base. • Urine pH is lower than blood pH • Kidneys- Acidification of urine.

  33. Contd… • Excretion of hydrogen ions • Reabsorption of bicarbonate ion • Excretion of ammonium ions

  34. Disorders of acid-base regulation cont… • Respiratory acidosis • Respiratory alkalosis • Metabolic acidosis • Metabolic alkalosis

  35. Contd… • Respiratory acid-base disorders are initiated by an increase or decrease in partial pressure of carbondioxide whereas metabolic disorders are initiated by an increase or decrease in bicarbonate ion.

  36. Contd… • Alkalosis - Partial pressure of oxygen increases. • Acidosis – Partial pressure of carbondioxide increases.

  37. Contd… Respiratory acidosis- • Decrease in rate of pulmonary ventilation- • Increased pCO2 of ECF. Respiratory alkalosis- • Increased rate of ventilation- • Decrease the pCO2

  38. Respiratory acidosis Figure 27.12a

  39. Respiratory alkalosis Figure 27.12b

  40. Contd… • Metabolic acidosis- • Decreased ECF bicarbonate ion conc. • Metabolic alkalosis- • Increased ECF bicarbonate ion conc.

  41. Contd…

  42. Contd… • Causes - Metabolic acidosis • 1. Renal tubular acidosis • 2. Diarrhea • 3. Vomiting of intestinal contents • 4. Diabetes Mellitus • 5. Ingestion of acids • 6. Chronic renal failure

  43. Contd… • Causes- Metabolic alkalosis • 1. Vomiting of gastric contents • 2. Ingestion of alkaline drugs etc.

  44. Correction by renal for… • Acidosis- • Increased excretion of hydrogen ions and addition of bicarbonate ions to the ECF. • Alkalosis- • Decreased tubular secretion of hydrogen ions and increased excretion of HCO3_

  45. The Central Role of the Carbonic Acid-Bicarbonate Buffer System in the Regulation of Plasma pH Figure 27.11a

  46. The Central Role of the Carbonic Acid-Bicarbonate Buffer System in the Regulation of Plasma pH Figure 27.11b

  47. Acid-Base Disorders • Respiratory acid base disorders • Result when abnormal respiratory function causes rise or fall in CO2 in ECF • Metabolic acid-base disorders • Generation of organic or fixed acids • Anything affecting concentration of bicarbonate ions in ECF

  48. Respiratory acidosis • Results from excessive levels of CO2 in body fluids

  49. Respiratory alkalosis • Relatively rare condition • Associated with hyperventilation

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