Page 68 - Color Atlas of Biochemistry

Amino Acids 59

A. Amino acids: functions

Components of: Precursors of:
Peptides Keto acids
Proteins Biogenic amines
Phospholipids Glucose
Nucleotides
Heme, creatine

Neurotransmitters: Transport molecule for:

R
Glutamate
Aspartate NH2 groups
Glycine

L-Amino acid

B. Optical activity

COO COO

COO COO
C C
H 3N R H 3N C H H C H 3N R H 3N
R R
H H
L-Amino acid D-Amino acid
Fischer projections (mirror image)

C. Dissociation curve of histidine

COOH pH COO
H N C H
H N C H 2 3
3
pK 1
CH 2 1.8 CH 2
4 C
C
HN CH HN CH
HC NH
HC NH 6 pK 2
6.0
pH 0.5 pH 5

COO 8 COO
pK 3
H N C H 9.2 H N C H
3
2
10
CH 2 CH 2
C C
HN CH 12 HN CH
HC N HC N

pH 7.6 -1 0 +1 +2 pH 11
(Isoelectric point)
Net charge

Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Thieme
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