L-Cysteine bụ otu n'ime amino asịd 20 eke, ma e wezụga methionine, naanị otu nwere sọlfọ.Ọ bụ thiol nwere amino acid na-adịghị mkpa nke oxidized na-etolite Cystine.Ọ bụ ihe na-adịghị mkpa sọlfọ nwere amino acid na ụmụ mmadụ, metụtara cystine, Cysteine dị mkpa maka njikọ protein, detoxification, na ọrụ metabolic dị iche iche.Achọpụtara na beta-keratin, protein bụ isi na mbọ, akpụkpọ ahụ, na ntutu isi, Cysteine dị mkpa na mmepụta nke collagen, yana nhịahụ na ọdịdị akpụkpọ ahụ.