Biological acids Henderson-Hasselbalch

The Henderson-Hasselbalch equation provides a general solution to the quantitative treatment of acid-base equilibria in biological systems. Table 2.4 gives the acid dissociation constants and values for some weak electrolytes of biochemical interest. 

Chapter 20, Carboxylic Aciils and Nitriles—A new Section 20.3 discusses biological carboxylic acids and the Henderson-Hasselbalch equation. 

June 3, 1978, Lynn, Massachusetts, USA - Feb. 10, 1942 Boston, USA) Henderson studied medicine at Harvard and was Professor of Biological Chemistry at Harvard University, Cambridge, Massachusetts, from 1904 to 1942 [i]. Henderson published on the physiological role of -> buffers [ii-vii] and the relation of medicine to fundamental science. Because he and also - Hasselbalch made use of the law of mass action to calculate the - pH of solutions containing corresponding acid-base pairs, the buffer equation is frequently (esp. in the biological sciences) referred to as -> Henderson-Hasselbalch equation. 

Biological acids the Henderson-Hasselbalch equation (Section 20.3)... 

When a weakly acidic or basic drug is administered to the body, the drug will ionise to a greater or lesser extent depending on its piCa and the pH of the body fluid in which it is dissolved. The pH of the body varies widely, but the most important biological solution is the blood, which, as stated above, normally has a pH of 7.4. An equation can be derived that will predict the extent to which the drug ionises, and, as is often the case, the starting point for the derivation is the Henderson-Hasselbalch equation (1.7). 

The Henderson-Hasselbalch equation was developed independently by the Ameriean biological chemist L. J. Henderson and the Swedish physiologist K. A. Hasselbaleh, for relating the pH to the bicarbonate buffer system of the blood (see below). In its general form, the Henderson-Hasselbalch equation is a useful expression for buffer caleulations. It can be derived from the equilibrium constant expression for a dissociation reaction of the general weak acid (HA) in Equation (1.3) ... 

The degree of drug ionization depends upon both the pH of the solution in which it is presented to the biological membrane and on the pKa (dissociation constant) of the drug (whether it is an acid or base). The entire concept of pKa is derived from the Henderson-Hasselbalch equation for both acids and bases as follows ... 

This equation is known as the Henderson—Hasselbalch equation. Workers in the biological sciences use it frequendy. Because the amount of weak acid dissociated is very small, the values for [conjugate base] and [acid] are essentially their initial concentrations after mixing, ignoring the negligible reaction that they then undergo. 

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