BIOL 0280 Lecture Notes - Lecture 1: Titration, Zwitterion, Hydrolysis
9 Nov 2016
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Document Summary
Parts of an amino acid: amino group, acid/carboxyl group, alpha-c, side chain. Stereochemistry: most amino acids are s but some are r, chiral and achiral. N is on the left (in sugars, ho: absolute configuration. No priority rules - stereochemistry is defined by configuration, not priority. Optical activity: chiral molecules are optically active. Direction plane of linear polarized light passing through is rotated. Rotation to the right: (+: some amino acids rotate it one way, some rotate another way, racemic mixture has equal concentrations of l and d - optically inactive, *l- and d- designate chemical configuration not rotation direction. 20 amino acids normally occur in proteins: all chiral amino acids have l configuration. Grouped by chemical nature of side chains (r groups: nonpolar aliphatic r groups. Isoleucine has two stereocenters (d/l labels stereocenter of a-c only: negatively charged r groups (acidic, positively charged r groups. Histidine is conditionally positively charged: polar uncharged r groups.
