Acid Base Balance Lab Report

Acid base balance is a part of homeostasis for maintaining the pH of the body. It is necessary for the functioning of enzymes and structural integrity of proteins. In case of an unacceptably large variation in the pH of the body, the enzymes lose their normal function, the proteins get denatured, and in extreme cases, death might result. The normal pH of human blood is 7.4, the acceptable range being 7.35-7.45. In the foetus, the normal range differs based on which umbilical vessel is sampled (umbilical vein pH is normally 7.25 to 7.45; while umbilical artery pH is normally 7.18 to 7.38).[1] pH levels below 7.0 and above 7.7 are fatal. The body maintains this level by a number of regulatory mechanisms. A pH less than the normal range results in acidosis, while a pH more than the normal range is called alkalosis. The pH of the body is a cumulative effect of a number of acids produced in the body on a daily basis due to various metabolic processes and also the HCO3- and other ions that neutralize them. The acids produced are of two types: respiratory or volatile acids (which can be excreted by the lungs) like H2CO3, which is produced from carbon dioxide and water by the action of carbonic anhydrase; and metabolic or fixed acids, which cannot be excreted by the lungs like lactate, phosphate, sulphate, acetoacetate, b-hydroxybutyrate, or any other acid in the body except carbonic acid. For acid base balance, the amount of acid produced in the body each day must be equal to the amount excreted. An imbalance in this can be broadly classified into four types: Respiratory acidosis: Primarily caused due to excess CO2 which forms excess H2CO3. Respiratory alkalosis: Due to excess loss of CO2 and low CO2 levels in blood. Metabolic acidosis: Due to excess fixed acids production or decreased excretion. Metabolic alkalosis: Due to excess excretion or loss of metabolic acids from the body. In case of a variation in pH outside the normal range, the body corrects it in three ways, in the order:[2] • Buffer action • Respiratory compensation • Renal compensatory mechanism The mode of action of these mechanisms is as follows: The buffer whose pKa value is nearest to the physiological pH of blood(7.4) is the most effective in its action. …show more content…
The phosphate buffer system(pKa=6.8) has very low concentration in blood. Hence its effect can be practically neglected compared to bicarbonate buffer system(pKa=6.1). The normal bicarbonate level in blood is 22-26 meq/L. The effective pH of the buffered solution can be calculated by the Henderson-Hasselbalch equation as: pH = pKa + log10 ( [HCO3] / 0.03 x pCO2)
The general equation for the action of bicarbonate buffer is:
CO2 + H2O <==C.A.==> H2CO3 <====> H+ + HCO3-

RESPIRATORY COMPENSATION
Compensation by this system is more important in case of metabolic acidosis or alkalosis. The pH is sensed by the central and peripheral chemoreceptors and integrated by the medulla which causes appropriate action by controlling the respiratory rate and volume. Acidosis causes hyperventilation causing the release of CO2 and hence the volatile acid H2CO3 normalizing the pH. Alkalosis causes hypoventilation and retention of CO2 and hence doesn’t allow the pH to rise.

RENAL COMPENSATION
Kidneys play an important role in the long term regulation of pH. It does so by regulating acid excretion, bicarbonate reabsorption, H+ secretion and ammonium ion secretion. About 85 to 90%