BCHM 3050 1st Edition Lecture 5Outline of Last Lecture I. Weak AcidsII. Ionization of WaterIII. Buffers IV. Henderson-Hasselbalch EquationV. Types of Buffers VI. Amino AcidsOutline of Current Lecture I. Isoelectric Point = pIa. Nature of an Amino Acidb. Nonpolar Amino Acidsc. Acidic Amino Acidsd. Basic Amino AcidsCurrent LectureI. Isoelectric Point = pIa. Nature of an Amino Acidi. When determining the nature of an amino acid, just look at the “R” group(the rest of the amino acid is considered the “backbone”)ii. The R group determines if the amino acid is polar, nonpolar, acidic, or basicb. Nonpolar Amino Acidsi. At extremely low pH, amino acid will hold onto the protonii. At pH of zero, most amino acids that are nonpolar will has a net charge of +1iii. At pK = 2.3, proton will leave COOH group to create COO-1. pH at which 50% carboxylic acid groups have charge of zero and 50% have charge of +1iv. At pK = 6.0, all COOH lost protons to become COO-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.v. At pK = 9.7, 50% NH3 and 50% NH2vi. pI = the average of 2.3 and 9.7, which is 6.0c. Acidic Amino Acidsi. For Aspartic Acid, at pH of 2.1, 50% has a charge of +1 and 50% has a charge of 0ii. At 3.9, 50% has charge of 0 and 50% has charge of -1iii. Amino group loses protons lastiv. pI of acidic amino acid = average the pK of the 2 carboxylic acid group (DONOT take into account the pK of the amino group)v. Average pK-1 and pK-2 for ACIDIC AMINO ACIDS (ignore pK-3)d. Basic Amino Acidsi. For Basic amino acids, pI = (pK-2 + pK-3)/2ii. Average the two higher numbersiii. Ignore the pK-1
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