Amino acids group 2- electrically neutral polar side chains

Which amino acids have electrically neutral polar side chains (Group 2)... 

Which amino acids have electrically neutral polar side chains (Group 2) A second group of amino acids has side chains that contain electronegative atoms such as oxygen, nitrogen, and sulfur. 

Four groups of amino acids are found in proteins first, those with nonpolar side chains second, those with electrically neutral polar side chains third, those with carboxyl groups in their side chains fourth, those with basic side chains. 

Another group of amino acids has polar side chains that are electrically neutral (uncharged) at neutral pH. This group includes serine, threonine, tyrosine. 

Different side chain groups determine the type of a given amino acid. These side chains can be classified as neutral, acidic, or basic aliphatic or aromatic hydrophobic or polar, etc. As discussed previously, the piezoelectricity and pyroelectricity requires restrictions on crystal symmetry (e.g., 20 crystallographic groups can be piezoelectric, and only 10 groups demonstrates pyroelectricity). The piezoelectric response of amino acids to the high-frequency electric pulses is shown in Table 48.7 the pyroelectric properties of amino acids were also measured, but found not significant [44]. 

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