The part of one type of amino acid that makes it different from another type is

Amino acids carry two functional groups: an amine group (-NH2) and a carboxylic acid group (-COOH). They are different because they have different side chains (R groups) attached to an alpha carbon that is specific to each amino acid.

Key elements in the 500 amino acids are carbon, hydrogen, oxygen, and nitrogen, but other elements can be found in the side chains of certain amino acids.

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answer; i believe the correct answer is ( proteins );