Cell requires optimal amount of nutrients for the synthesis of macromolecules like lipid, protein and nucleotides. There is a very limited knowledge about how cells maintain homeostasis in excess nutrients. By using Yeast as a model system we have shown that some aminoacids are toxic at higher concentration. We have chosen cysteine as a physiologically relevant example and using proteomics approach we delineated the altered pathways/ metabolic processes .We found that cysteine alters proteins mainly involved in amino acid metabolism, energy metabolism and proteins involved in translation.