Proteins may be broken into their constitutent monomer molecules by hydrolysis. AminoAcid products of the reaction constitute the AminoAcid composition of the Proteins.

• Standard AminoAcid : 20 amino acids found in Proteins

• Nonstandard AminoAcid : chemically mdified after their incorporation into a polypeptide and amino acids that occur in living organisms but are not found in Proteins. e.g.taurin

These molecules contain a central carbon atom (alpha-carbon) to which an amino group, a carboxylate group, a hydrogen atom, and an R(side chain) group are attached.

At a pH of 7 the carboxyl group of an AminoAcid is in its conjugate base form (-COO-) and the amino group is in its conjugate acid form (-NH3+). Thus each AminoAcid can behave as either an acid or a base. It's called Amphoteric property of a AminoAcid. Neutral molecules that bear an equal number of positive and negative charges simultaneously are called zwitterions. It is the R group, however, that gives each AminoAcid its unique properities. Also the pH value that AminoAcid's net charge become zero is called IsoelectricPoint.

Names and Abbreviations of the Standard amino acids

Special AminoAcid

Classification of Amino acids

• Group I : Hydrophobic - Nonpolar side Chains
  • Ala, Val, Leu, Ile, Pro, Met, Phe, Trp
  Group II : Polar, unchanged
  • Gly, Ser, Thr, Cys,Tyr, Asn, Gln
  Group III : Acidic
  • Asp, Glu
  Group IV : Basic
  • Lys, Arg, His

Properties of each Amino acids

♣Histidine(His, H)

• Unique imidazole side chain: effective as nucleophilic catalyst( more basic than hydroxide ion)

  five-membered ring structure --> relatively little steric hindrance pKa = 7

<Aromatic Residues>

• Has UV absorbance and fluorescence properties of proteins.

AminoAcid chart

필수 AminoAcid

체내에서 합성이 되지 않기 때문에 반드시 섭취해야 하는 8가지 AminoAcid들

• Ile, Leu, Val, Lys, Phe, Trp, Met, Thr