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Title: Amino acids
Description: These are the instant summary for Amino Acids Biochemistry
Description: These are the instant summary for Amino Acids Biochemistry
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Amino acids
Amino acids are the building blocks of proteins
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Nineteen of these are α-amino acids with a
primary amino group (–NH3) and a carboxylic acid (carboxyl; –COOH) group attached to a central carbon
atom, which is called the -carbon atom (Cα) because it is adjacent to the carboxyl group (Fig
...
Also
attached to the Cα atom is a hydrogen atom and a variable side-chain or ‘R’ group
...
The
Name of the amino acids are often abbreviated, either to three letters or to a Single letter
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Enantiomers
All of the amino acids, except for glycine, have four different groups arranged tetrahedrally around the
central Cα atom which is thus known as an asymmetric center or chiral center and has the property of
chirality
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Enantiomers are
physically and chemically indistinguishable by most techniques, but can be distinguished on the basis of
their different optical rotation of plane-polarized light
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D- and L-amino acids can also be distinguished by enzymes which usually only
recognize one or other enantiomer
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D-Amino acids rarely
occur in nature, but are found in
Bacterial cell walls and certain antibiotics
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They can be subdivided into smaller groupings on the basis of similarities in the properties of
their side-chains
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Some are acidic, others are basic
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Some have aromatic side-chains, others are polar
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Some are chemically reactive
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The aliphatic side-chains of alanine (Ala or A), valine (Val or V),
Leucine (Leu or L), isoleucine (Ile or I) and methionine (Met or M) are chemically unreactive, but
hydrophobic in nature
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The sulfur-containing side-chain of cysteine
(Cys or C) is also hydrophobic and is highly reactive, capable of
Reacting with another cysteine to form a disulfide bond
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Polar, charged amino acids
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The amino groups on the side-chains of the basic amino acids arginine
(Arg or R) and lysine (Lys or K) are protonated and thus positively charged at neutral pH
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In contrast, at neutral pH the carboxyl groups on the side-chains of the acidic
Amino acids aspartic acid (aspartate; Asp or D) and glutamic acid (glutamate;
Glu or E) are de-protonated and possess a negative charge
...
The side-chains of asparagine (Asn or N) and glutamine (Gln or Q), the
Amide derivatives of Asp and Glu, respectively, are uncharged but can participate in hydrogen bonding
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Title: Amino acids
Description: These are the instant summary for Amino Acids Biochemistry
Description: These are the instant summary for Amino Acids Biochemistry