Fundamentals of
Biochemistry
Third Edition
Donald Voet • Judith G. Voet •
Charlotte W. Pratt
Chapter 4
Amino Acids
Copyright © 2008 by John Wiley & Sons, Inc.
Section 1 – Amino Acid Structure
zwitterions
Titration of Glycine
pI – isoelectic point of an
amino acid or protein. The pH
at which a protein or amino
acid has no net charge.
Formation of Peptide bond
H2 O
A
W
D
G
Two representations of an amino acid at neutral pH
(a) Structure
(b) Ball-and stick model
Stereochemistry
• Stereoisomers - compounds that have the same
molecular formula but differ in the arrangement of
atoms in space
• Enantiomers - nonsuperimposable mirror images
• Chiral carbons - have four different groups
attached
• RS – nomenclature is not used for amino acids
• LD – nomenclature used for amino acids
L=levo: rotates polarized light to the left
D=dextro: rotates polarized light to the right
Section 3 – Amino Acid Derivatives
Aequorea victoria
Practice: Questions: 1, 3 – 12, 15 – 17