This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Glutathione is: 
Select and explain. 
A. Dipeptide, B. Oligopeptide, C. Tripeptide, D. Polypeptide
C: Tripeptide
Answer: C: Tripeptide 
Explanation: Glutathione (GSH) is a tripeptide. It contains an unusual peptide linkage between the amine group of cysteine and the carboxyl group of the glutamate side chain. Glutathione, anantioxidant, helps protect cells from reactive oxygen species such as free radicals and peroxides. Glutathione is not an essential nutrient since it can be synthesized from the amino acids L-cysteine, L-glutamic acid and glycine.