Glutathione conjugation belongs to which phase of metabolism according to the source?

• A. Phase I metabolism or Conjugation phase
• B. Phase II metabolism or Functionalization phase
• C. Phase I metabolism or Functionalization phase
• D. Phase II metabolism or Conjugation phase

Answer: (C)

Glutathione conjugation is a Phase II metabolism process, the Conjugation phase. In this stage, the body attaches an endogenous molecule to a drug or its Phase I metabolite to boost water solubility and enable excretion. Glutathione S-transferases catalyze the attachment of glutathione to reactive sites on xenobiotics, producing a conjugate that’s more polar and readily eliminated in urine or bile. Phase I reactions, by contrast, are functionalization steps like oxidation, reduction, or hydrolysis that introduce or reveal reactive groups but don’t add glutathione. So the correct pairing is Phase II metabolism or Conjugation phase.