Amino Acids Structure Variations — NEET Biology

The R group (side chain) of amino acids determines their identity and properties. While glycine has R=H and alanine has a methyl group, students often confuse which R groups contain special elements like sulphur or oxygen. The NEET trap: assuming all amino acids contain similar functional groups—glycine is the simplest (no R group complexity), while others like cysteine have sulphur, and serine/threonine have hydroxyl groups. Key to remember: glycine's R=H makes it unique (smallest, no chiral center), and each R group's chemical nature (polar, nonpolar, charged, or containing sulphur) affects protein folding and function. This concept appears because identifying amino acids by their R groups is fundamental to biochemistry.