What monomers are proteins made of? What is the structure of the monomer that makes up a protein?

proteins have amino acids as monomers
are made up of 21 different L-amino acids. these amino acids are joined together with peptide bonds. peptide bond is a bond between a caboxylic group of one amino acid with amino group of other amino acid.
following is a figure to describe the structure of a single amino acid, where R -group is variable and can contribute for the amino acid to be neutral, acidic or basic. next figure gives an idea of how many various amino acids are there.https://d2gne97vdumgn3.cloudfront.net/api/file/4T2yi8oSO61z3UYvgGqf
various amino acidshttps://d2gne97vdumgn3.cloudfront.net/api/file/KmI7dyrDRQGnlyq5EMhK
everybody is welcome for any suggestion for updating the answer
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