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Regulation of [H + ]

Regulation of [H + ]. Acid-Base Physiology. pH vs [H + ]. Why is it important to regulate [H + ]?. H 2 O H + + OH -.

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Regulation of [H + ]

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  1. Regulation of [H+] Acid-Base Physiology.

  2. pH vs [H+]

  3. Why is it important to regulate [H+]?

  4. H2OH+ + OH- • Because of covalent bonding between O2 and H, water has little tendency to dissociate the reaction is always far to the left. At equilibrium the concentrations of H+ and OH- are very small.

  5. Electrical Neutrality • Essential to understanding A-B physiology. • In a solution at equilibrium, Σ of + charges always equal to Σ of – charges. • [H+] = [OH-] • [H+]+[Na+] = [OH-]+[Cl-]

  6. Strong Ions • NaCl is a strong electrolyte. NaCl Na+ + Cl- • In solution we have Na+ and Cl- but no NaCl.

  7. Strong Ion Difference (SID). • The sum of all positive strong ions minus the sum of all negative strong ions. • SID = (Σ + ions) - (Σ - ions). • SID = ([Na+]+[K+]+[Ca++]) - ([Cl-]+[Lact-])

  8. Negative SID  acid • Positive SID  alkaline

  9. Strong Ions and Carbon Dioxide • Adding CO2 to a solution with a positive [SID] has a dramatic effect on [H+]. • CO2 + H2O <--> H2CO3 <--> HCO3- + H+ • CO2 pushes this equation to the right and therefore increases[H+] which decreases pH.

  10. How does the body regulate [H+]? • By controlling the independent variables. • Respiratory system controls PCO2 . • Renal system controls SID, mostly by controlling [Cl-]. • Slight disturbances in pH can have serious consequences.

  11. Buffers • Buffers resist changes in pH by converting strong acids or bases to weak ones

  12. Physiologic Buffers • Body systems that control output of acids, bases, or CO2 and thus stabilize pH • Respiratory System • HCO3- + H+ <--> H2CO3 <--> CO2 (expired) + H2O • Urinary/Excretory System (can regulate H+ secretion into urine)

  13. Buffer Systems = Chemical Buffers • Systems that quickly bind or release hydrogen ions

  14. Bicarbonate Buffer System • CO2 + H2O <--> H2CO3 <--> HCO3- + H+ • Carbonic Acid is a weak acid • Enzymes work best at pH of 6.1 • Reaction to right lowers pH • Reaction to left raises pH

  15. Phosphate Buffer System • H2PO4- <--> HPO42- + H+ • Reaction to right lowers pH • Reaction to left raises pH • Enzymes work ideally at pH of 6.8

  16. Protein Buffer System – most common buffer system • Carboxyl groups on amino acids • --COOH --> --COO- + H+ • Here it is acting like an acid as a proton donor • Amino groups on amino acids • --NH2 + H+ --> --NH3+ • Here it is acting like a base, a proton acceptor

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