PHIS 206 1st Edition Lecture 23 Outline of Last Lecture I Regulation II If Ascending Descending Not Parallel III Countercurrent Importance IV Hypothalamus V Balance VI Normal Body Fluids VII Regulation of H Concentration Outline of Current Lecture I Hydrogen Concentration II Dissociation of Acids III Weak v Strong Acids IV Physiology V How to get rid of H in plasma VI Pathological VII How to Maintain Normal pH VIII Chemical Buffers IX Respiratory System X Renal XI Acidosis v Alkalosis Current Lecture I Hydrogen Concentration ph log H each log change is a 10 fold change in H concentrations H log H pH 6 10 6 6 10 7 7 7 10 8 8 8 pH changes 1 then 10 fold change in H concentration H goes up pH goes down II Dissociation of Acids acid adds H in solution These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute HA H A equilibrium k HA H A We can take log k pK NOTE k equilibrium constant When pH pK of acid then acid is 50 dissociated and 50 associated Graphical Representation 100 50 Dissociation pK pH III Weak v Strong Acids strong acid largely dissociated at low pH EX HCl pH 1 2 pK small weak acid dissociated when at high pH EX acetic acid pH 3 4 pK large If neighborhood of pK adding H or removing H will not make much of a difference acids adding or subtracting H of solution has less effect when pH is near pK every acid is called a buffer buffer acid buffers effects of adding or removing H 1 greatest when pH pK more buffering capacity 2 greatest when more concentrated acid more buffering capacity IV Physiology plasma pH H concentration in plasma plasma pH 7 4 o greater than 10 8 M less than 10 7 M venous 7 3 arterial 7 45 more outgoing plasma picks up carbon dioxide so more acidic increase CO2 increase H decrease pH CO2 lost in pulmonary capillaries Any plasma pH 7 4 ALKALOSIS Any plasma pH 7 4 ACIDOSIS Limits of plasma pH from 7 0 to 7 8 V How to get rid of H in plasma major source of H metabolism H in diet EX orange juice salad dressing H when digesting food We produce huge amounts of CO2 so increase in H and can cause alkalosis depresses neural activity cause coma hyperexcitability VI Pathological vomit acidity of stomach lost so negative H balance diarrhea losing alkaline solution acidity left behind VII How to Maintain Normal pH 3 Mechanisms to Maintain Constant Plasma pH 1 Chemical buffers in plasma 2 Respiratory system blow off CO2 increase plasma pH reduce acidity 3 Renal secrete H and control how much is secreted VIII Chemical Buffers Most important carbonic acid buffer CO2 H2O H2CO3 HCO3 H k HCO3 H CO2 pK 6 1 little buffering 2nd major chemical buffer proteins concentration low ranges above plasma pH and below plasma pH proteins only EXIST in plasma not ICF Hemoglobin pK not close to pH Phosphate buffer great buffer b c pK close to plasma problem little phosphate in plasma All good potential buffers but conc are low so capacity is also low IX Respiratory System can control rate of CO2 by controlling alveolar ventilation has an enormous capacity of moving CO2 out suspend respiration then you double H in less than a minute b c you CO 2 is held in bring system back to 7 4 bring to 7 1 7 35 but never quite 7 4 respiratory system is IMPRECISE X Renal secrete H in urine rate of secretion is precisely related to plasma pH kidneys readjust imbalance of plasma pH However kidneys take hours to days to bring plasma pH to 7 4 XI Acidosis v Alkalosis Respiratory alkalosis hyperventilate acidosis snoring Metabolic alkalosis vomit acidosis diarrhea
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