BISC 330 Spring 2011 Lecture 3

# BISC 330 Spring 2011 Lecture 3 - BISC 330L: Biochemistry...

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BISC 330L: Biochemistry Spring Semester 2011 USC Lecture: Friday, 14 January 2011 1. Finish Chapter 1 material… Henderson Hasselbalch Discovery of DNA The Genomic Revolution

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Henderson Hasselbalch Equation For acid AH (proton donor in neutral form): AH A + H + K a = [A ][H + ]/[AH] logK a = log[H + ] + log([A ]/[AH]) log[H+] = logK a + log([A ]/[AH]) pH = pK a + log([A ]/[AH]) (Henderson Hasselbalch Equation) NOTE: [A ]/[AH] = 10 pH pKa [A ] = [AH](10 pH pKa ) [AH] = [A ]/(10 pH pKa ) ¾ Fraction ionized (f I = f A ): ¾ f I = [A ]/([A ]+[AH]) = (10 pH pKa )/(1 + 10 pH pKa )
pH f i = f A = 10 pH pKa /(1+10 pH pKa ) 3 + pKa 10 3 / (1+10 3 )= 0.001 2 + pKa 10 2 / (1+10 2 )= 0.01 1 + pKa 10 1 / (1+10 1 )= 0.1 pKa 1/ (1+1) = 0.5 1 + pKa 10 1 / (1+10 1 )= 0.9 2 + pKa 10 2 / (1+10 2 )= 0.99 3 + pKa 10 3 / (1+10 3 )= 0.999 Fraction ionized (f I = f A ): f I = [A ]/([A ]+[AH]) = (10 pH pKa )/(1 + 10 pH pKa )

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Graph of the data f i pH 3 + pK a 2 1
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## This note was uploaded on 02/15/2012 for the course BISC 330L taught by Professor Petruska,tower during the Spring '07 term at USC.

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BISC 330 Spring 2011 Lecture 3 - BISC 330L: Biochemistry...

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