ZieglerLecture3-AminoAcids-ppt6 - 1. Learning Objectives...

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1 Lecture 3: Amino Acids and Peptides Peptides BIOCHEMISTRY 100 Winter 2009 M. Ziegler Learning Objectives Learning Objectives 1. Terminology (explain or defne; understand use oF terms) : α -amino acid, side chain, R group, amino group, carboxyl group, aliphatic, aromatic, indole, hydroxyl, thiol (sulfhydryl), imidazole, guanidino, isoelectric pH (pI), amide, peptide bond 2. Learn the structure oF each oF the 20 amino acids, with its Full name and 3-letter abbreviation. DO THIS NOW – DON ʼ T PUT IT O±±. You won't have to draw detailed structures of arginine or tryptophan, but you should be able to recognize them, and draw the other structures, with the ionization reactions of ionizable groups (see below). Draw the structure of a ʻ generic ʼ α -amino acid, and given the name or 3-letter or 1-letter abbreviation of any of the 20 amino acids, draw its structure. 3. Are the 20 amino acids found in proteins the D- or L-isomers? 4. Name the functional groups on the side chains of Ala, Asn, Gln, Ser, Thr, Cys, Tyr, Trp, Asp, Glu, His, Lys, Arg. 5. Know the Greek letters up through epsilon: alpha ( α ), beta ( β ), gamma ( γ ), delta ( δ ), epsilon ( ε ). 6. Classify any amino acid side chain into any of the following categories that apply to it: nonpolar, polar but uncharged (pH 7), acidic, or basic; ionizable or non-ionizable; aliphatic or aromatic; S-containing; OH-containing. (Some amino acids fall into more than one of the above categories.) 7. For the 7 amino acids with ionizable side chains, be able to draw the side chain structure in its weak acid and in its conjugate base form; know which form is uncharged and which form is charged (and whether charged form is positively Learning Objectives, continued (7.) or negatively charged). You do NOT need to memorize the pK a values For the ionizable groups on the Free amino acids , but given the pK a of an amino acid functional group, be able to write the ionization reaction for that group. 8. Be able to sketch a titration curve (pH vs. equivalents of OH added) for any of the 20 amino acids and to explain what is happening to the molecule as the pH increases between 1 and 14. Be able to read pK a values off a titration curve and explain what species (states of ionization) are present at each pK a and at each integral equivalence point on the curve (1 equivalent of OH added, 2 equivalents added, etc.) 9. Given the pK a for an ionizable functional group and the pH of a solution, be able to state qualitatively which ionic state of that group predominates at that pH without the use of a calculator. 10. Be able to calculate (using the Henderson-Hasselbalch Equation or the de±nition of K a ), with a non-programmable calculator, the percentage of a functional group in a particular ionic state, given the pH of the solution and the pK a of the functional group. Given the percentage of the functional group in a particular ionic state and the pK a of the group, be able to calculate the pH of the solution.
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This note was uploaded on 02/25/2009 for the course BCH 100 taught by Professor Staff during the Spring '08 term at UC Riverside.

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ZieglerLecture3-AminoAcids-ppt6 - 1. Learning Objectives...

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