CH250 Lecture Notes - Lecture 32: Aromatic Amino Acids, Tryptophan, Phenylalanine
Document Summary
Tryptophan: largest aa due to bicyclic ring structure; occurs least frequently in proteins (1. 4%) Figure 4. 13 there are three aromatic amino acids: phenylalanine, tyrosine, and tryptophan. These amino acids absorb ultraviolet light and provide a useful way to measure protein concentration in solutions. Hydrolysis: water added to break peptide bonds (ie. digestion) Figure 4. 17 amino acids are joined together by peptide bonds. In cells, a similar reaction is catalyzed by ribosomes. In cells, peptide bond cleavage is catalyzed by enzymes called proteases. The growing peptide has a single amino terminus (n terminus) and a single carboxyl terminus (c terminus). Figure 4. 18 a four-amino-acid segment of a polypeptide, which is linked together by three peptide bonds, is shown here. a. Arg169-his170 showing the amino acid side chains in red. b. molecular structure of this same tetrapeptide within the phenylalanine hydroxylase protein with the c carbons colored in gold. Titin: very large molecular mass, contains a lot of amino acids.
