Classifying amino acids by side chain
Because the side chains of the amino acids are important in determining many properties of the polypeptide, it is useful to group amino acids according to classifications that are relevant to polypeptide properties.
Amino acids that have acidic or basic groups in their side-chains are classed as electrically charged because at pH 7
Like the bonds in the polypeptide chain, the bonds in amino acid side chains are covalent.
Electron pairs are shared between covalently bonded atoms.
If the sharing is unequal, the bond is described as polar because one of the bonded atoms is slightly negative and the other slightly positive.
N-H, C=O, O-H and S-H bonds are polar. Amino acids that are not electrically charged but have side-chains with polar bonds are classed as polar.
Other amino acids are classed as nonpolar.
Nonpolar amino acids often have only C-H bonds in their side chain.
the acid -CO2H donates H+ to water and exists as -CO2–
basic nitrogen accepts H+ from water to form -NH+-
basic nitrogen accepts H+ from water to form -NH+-
Like the bonds in the polypeptide chain, the bonds in amino acid side chains are covalent.
Electron pairs are shared between covalently bonded atoms.
If the sharing is unequal, the bond is described as polar because one of the bonded atoms is slightly negative and the other slightly positive.
N-H, C=O, O-H and S-H bonds are polar. Amino acids that are not electrically charged but have side-chains with polar bonds are classed as polar.Other amino acids are classed as nonpolar. Nonpolar amino acids often have only C-H bonds in their side chain.