Answer:
Cysteine is an amino acid that contains a thiol group (-SH) in its side chain. It has a central carbon atom that is bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and a sulfhydryl group (-SH). These four groups are attached to the central carbon atom, which makes cysteine a chiral molecule that exists in two mirror-image forms. In biological systems, cysteine plays an important role in protein structure and function, as well as in various metabolic processes. The sulfhydryl group in cysteine is particularly reactive and can form disulfide bonds with other cysteine residues in proteins, which contribute to protein stability and conformation.
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