BIOL 4093 Chapter : Ch 2 Outline
Document Summary
This ionization form of proteins varies with changes in ph (zwitterion dominates at physiological ph): twenty kinds of side chains varying in size, shape, charge, hydrogen bonding capacity, hydrophobic character, and chemical reactivity are commonly found in proteins. The only one that is achiral: alanine-next simplest. Side chain has additional chiral center but only one isomer is found in proteins. The larger hydrophobic portions cluster together in water: valine, methionine-largely aliphatic side chain with thioester group, proline-conformational restriction, phenylalanine-aromatic. Less hydrophobis due to nh groups: polar amino acids with neutral r groups but the charge is not evenly distributed, serine-have hydroxyl group on hydrophobic chains, making them much more hydrophilic. Two thiol groups can react and form a disulfide bond, which stabilizes proteins greatly: positively charged amino acids with r groups that have a positive charge at physiological ph, lysine-hydrophilic due to positive charge. Positive charge at physiological ph: arginine-same, histadine-has imidazole group, aromatic ring that can be positively charged.
