Transcript CH_16_3_Formation_Peptides

Chapter 16 Amino Acids, Proteins,
and Enzymes
1
16.3
Formation of Peptides
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Formation of Peptides
2
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
O
CH3 O
+
||
|
||
+
H3N—CH2—C—O– + H3N—CH—C—O–
O H CH3 O
|| |
|
||
+
H3N—CH2—C—N—CH—C—O–
peptide bond
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Formation of a Dipeptide
3
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
4
Write the dipeptide Ser-Thr.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
5
Write the dipeptide Ser-Thr.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Naming Peptides
6
A peptide
• is named with names of all amino acids in the peptide using
a -yl ending for the name
• is named using the full amino acid name for the amino acid
at the the C terminal
N Terminal
C Terminal
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
7
Write the names and three-letter abbreviations of the
tripeptides that could form from two glycines and one alanine.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
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
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
9
What are the possible tripeptides formed from one each of
leucine, glycine, and alanine?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
10
Tripeptides possible 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
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
11
Write the three-letter abbreviation and name for the
following tetrapeptide.
CH3
CH3
CH–CH3 SH
S
CH2
CH3 O H CH O H CH2 O H CH2 O
+
H3N–CH–C–N–CH–C–N–CH–C–N–CH–C–O–
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
12
Ala-Leu-Cys-Met
Alanylleucylcysteinylmethionine
CH3
CH3
CH–CH3 SH
S
CH2
CH3 O H CH O H CH2 O H CH2 O
+
H3N–CH–C–N–CH–C–N–CH–C–N–CH–C–O–
Alanine Leucine Cysteine Methionine
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.