General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.1 Chapter 19 Amino Acids and Proteins 19.3 Formation of Peptides

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.2 The Peptide Bond A peptide bond  is an amide bond  forms between the carboxyl group of one amino acid and the amino group of the next amino acid  contains an N (free H 3 N + ) terminal written on the left  contains a C (free COO – ) terminal written on the right

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.3 Formation of a Dipeptide

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.4 Naming Dipeptides A dipeptide is named with  a yl ending for the N-terminal (free H 3 N + ) amino acid  the full amino acid name of the free carboxyl group (COO – ) at the C-terminal end

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.5 Learning Check Draw the condensed structural formula, and give the name and abbreviation for the dipeptide Ser-Thr.

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.6 Solution

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.7 Write the names and three-letter abbreviations of the tripeptides that could form from two glycines and one alanine. Learning Check

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.8 Write the names and three-letter abbreviations of the tripeptides that could form from two glycines and one alanine. Glycylglycylalanine Gly-Gly-Ala Glycylalanylglycine Gly-Ala-Gly Alanylglycylglycine Ala-Gly-Gly Solution

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.9 Learning Check What are the possible tripeptides formed from one each of leucine, glycine, and alanine?

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.10 Solution What are the possible tripeptides formed from one each of leucine, glycine, and alanine? Leu-Gly-Ala Leu-Ala-Gly Ala-Leu-Gly Ala-Gly-Leu Gly-Ala-Leu Gly-Leu-Ala

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.11 Learning Check Write the name and three-letter abbreviation for the following tetrapeptide:

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.12 Solution Ala-Leu-Cys-MetAlanylleucylcysteylmethionine