Amino acids
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Glycine (Gly, G) *
Category: Nonpolar, Aliphatic
Structure: Smallest amino acid, hydrogen as its side chain
Special Group: Simplest amino acid
Properties:
Flexible due to small size
Often found in protein turns and loops
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Alanine (Ala, A) *
Category: Nonpolar, Aliphatic
Structure: Methyl group (-CH₃) side chain
Special Group: Small and simple
Properties:
Hydrophobic
Found in protein interiors
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Valine (Val, V) *
Category: Nonpolar, Aliphatic
Structure: Branched-chain, isopropyl group
Special Group: Branched-chain amino acid (BCAA)
Properties:
Hydrophobic
Found in protein interiors and contributes to stability
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Leucine (Leu, L) *
Category: Nonpolar, Aliphatic
Structure: Branched-chain, isobutyl group
Special Group: Branched-chain amino acid (BCAA)
Properties:
Hydrophobic
Essential amino acid, important for muscle building
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Isoleucine (Ile, I) *
Category: Nonpolar, Aliphatic
Structure: Branched-chain, sec-butyl group
Special Group: Branched-chain amino acid (BCAA)
Properties:
Hydrophobic
Essential amino acid, contributes to protein stability
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Proline (Pro, P) *
Category: Nonpolar, Aliphatic
Structure: Cyclic, secondary amine
Special Group: Imino acid (unique ring structure)
Properties:
Causes kinks in protein chains
Found in turns and loops of proteins
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Methionine (Met, M) *
Category: Nonpolar, Aliphatic
Structure: Sulfur-containing thioether group
Special Group: Sulfur-containing
Properties:
Hydrophobic
Initiator amino acid for protein synthesis
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Phenylalanine (Phe, F) *
Category: Aromatic
Structure: Benzyl group (aromatic ring)
Special Group: Aromatic amino acid
Properties:
Hydrophobic
Found in protein interiors, important for protein stability
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Tyrosine (Tyr, Y) *
Category: Aromatic
Structure: Phenolic group (aromatic ring with -OH)
Special Group: Aromatic amino acid, polar
Properties:
Can form hydrogen bonds due to hydroxyl group
Precursor to neurotransmitters like dopamine
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Tryptophan (Trp, W) *
Category: Aromatic
Structure: Indole ring
Special Group: Aromatic amino acid, largest side chain
Properties:
Hydrophobic
Essential amino acid, precursor to serotonin
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Serine (Ser, S) *
Category: Polar, Uncharged
Structure: Hydroxymethyl group (-CH₂OH)
Special Group: Hydroxyl-containing amino acid
Properties:
Can form hydrogen bonds
Often involved in enzyme active sites
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Threonine (Thr, T) *
Category: Polar, Uncharged
Structure: Hydroxyl group (-OH) on a branched chain
Special Group: Hydroxyl-containing, essential amino acid
Properties:
Can form hydrogen bonds
Found on protein surfaces
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Cysteine (Cys, C) *
Category: Polar, Uncharged
Structure: Thiol (-SH) group
Special Group: Sulfur-containing, forms disulfide bonds
Properties:
Important in protein folding through disulfide bridges
Contributes to protein stability
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Asparagine (Asn, N) *
Category: Polar, Uncharged
Structure: Amide group (-CONH₂)
Special Group: Amide-containing
Properties:
Can form hydrogen bonds
Often found in protein surfaces
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Glutamine (Gln, Q) *
Category: Polar, Uncharged
Structure: Amide group (-CONH₂)
Special Group: Amide-containing
Properties:
Can form hydrogen bonds
Important for nitrogen metabolism
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Aspartic Acid (Asp, D) *
Category: Acidic (negatively charged)
Structure: Carboxyl group (-COOH)
Special Group: Acidic amino acid
Properties:
Negatively charged at physiological pH
Often involved in enzyme active sites
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Glutamic Acid (Glu, E) *
Category: Acidic (negatively charged)
Structure: Carboxyl group (-COOH)
Special Group: Acidic amino acid
Properties:
Negatively charged at physiological pH
Important in neurotransmission (as glutamate)
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Lysine (Lys, K) *
Category: Basic (positively charged)
Structure: Amino group (-NH₂)
Special Group: Basic amino acid
Properties:
Positively charged at physiological pH
Essential amino acid, involved in cross-linking collagen
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Arginine (Arg, R) *
Category: Basic (positively charged)
Structure: Guanidinium group
Special Group: Basic amino acid
Properties:
Positively charged at physiological pH
Important in nitric oxide synthesis
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Histidine (His, H) *
Category: Basic (positively charged)
Structure: Imidazole ring
Special Group: Basic, aromatic amino acid
Properties:
Can act as both proton donor and acceptor
Important in enzyme active sites
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Selenocysteine (Sec, U) *
Category: Special
Structure: Selenium-containing thiol group (-SeH)
Special Group: 21st amino acid, rare
Properties:
Found in certain enzymes, essential for redox reactions
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Pyrrolysine (Pyl, O) *
Category: Special
Structure: Pyrroline ring
Special Group: 22nd amino acid, rare
Properties:
Found in certain archaea and bacteria, used in methyltransferases
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