AMINO ACIDS
Functions of Amino Acids
● A variety of roles in metabolism.
○ The building blocks of proteins
○ Forming parts of coenzymes
○ As precursors for the biosynthesis of molecules such as heme
● Proteins are composed of 20 different amino acids (encoded by standard genetic code, construct
proteins in all species)
● Their molecules contain both amino and carboxyl groups attached to the same α-carbon (L-α-amino
acids)
● Their chemical structure influences the three dimensional structure of proteins
● They are important intermediates in metabolism (porphyrins, purines, pyrimidines, creatine, urea,
etc.)
● They can have hormonal and catalytic function
● Several genetic disorders are caused in amino acid metabolism errors (aminoaciduria - presence of
amino acids in urine)
Standard and Nonstandard Amino Acids
● More than 300 different amino acids have been described in nature
● Standard α-amino-acids:
○ Only 20 are commonly found as constituents of proteins
● Nonstandard amino acids:
○ Amino acid derivatives found in protein
○ Non-protein amino acid
Amino acids are substituted acids in which an amino group (NH2) has been substituted for a hydrogen
atom attached to the carbon in the alpha position.
General Structure of α-Amino Acids
(or R group, R = “Remainder of molecule”)
, Stereochemistry of Amino Acids
Configuration:
● For all the common amino acids except Glycine the α-carbon is bonded to four different groups
● The α-carbon atom is thus a chiral center
Classification of Amino Acids
Amino acids are generally divided into groups on the basis of their side chains (R groups). The most
helpful start is to separate amino acids into:
1. Nonpolar
2. Neutral polar
3. Charged polar
Nonpolar Amino Acids
- Only carbon and hydrogen in their side chains
- Generally unreactive but hydrophobic
- Determining the 3D structure of proteins (they tend to cluster on the inside of the molecule)
Neutral amino acids have the same number of amino acids and carboxylic acids.
Nonpolar (Hydrophobic) R Groups
Functions of Amino Acids
● A variety of roles in metabolism.
○ The building blocks of proteins
○ Forming parts of coenzymes
○ As precursors for the biosynthesis of molecules such as heme
● Proteins are composed of 20 different amino acids (encoded by standard genetic code, construct
proteins in all species)
● Their molecules contain both amino and carboxyl groups attached to the same α-carbon (L-α-amino
acids)
● Their chemical structure influences the three dimensional structure of proteins
● They are important intermediates in metabolism (porphyrins, purines, pyrimidines, creatine, urea,
etc.)
● They can have hormonal and catalytic function
● Several genetic disorders are caused in amino acid metabolism errors (aminoaciduria - presence of
amino acids in urine)
Standard and Nonstandard Amino Acids
● More than 300 different amino acids have been described in nature
● Standard α-amino-acids:
○ Only 20 are commonly found as constituents of proteins
● Nonstandard amino acids:
○ Amino acid derivatives found in protein
○ Non-protein amino acid
Amino acids are substituted acids in which an amino group (NH2) has been substituted for a hydrogen
atom attached to the carbon in the alpha position.
General Structure of α-Amino Acids
(or R group, R = “Remainder of molecule”)
, Stereochemistry of Amino Acids
Configuration:
● For all the common amino acids except Glycine the α-carbon is bonded to four different groups
● The α-carbon atom is thus a chiral center
Classification of Amino Acids
Amino acids are generally divided into groups on the basis of their side chains (R groups). The most
helpful start is to separate amino acids into:
1. Nonpolar
2. Neutral polar
3. Charged polar
Nonpolar Amino Acids
- Only carbon and hydrogen in their side chains
- Generally unreactive but hydrophobic
- Determining the 3D structure of proteins (they tend to cluster on the inside of the molecule)
Neutral amino acids have the same number of amino acids and carboxylic acids.
Nonpolar (Hydrophobic) R Groups
