Sulphur and Selenium Containing Biomolecules

Correct Answer: All the above

All three pairs are correctly matched:

• Sulphur-containing vitamins: Thiamine (B1) — contains a thiazole ring with sulphur; Biotin (B8) — contains a tetrahydrothiophene ring with sulphur.
• Sulphur-containing amino acids: Cysteine (–SH thiol group) and Methionine (–S–CH₃ thioether group). Also include homocysteine and taurine.
• Selenium-containing enzyme: Glutathione peroxidase — contains selenocysteine at its active site. It neutralises hydrogen peroxide and lipid hydroperoxides, protecting cell membranes.

Key Metalloenzymes to Remember

• Copper → Cytochrome oxidase, Uricase, Ceruloplasmin
• Zinc → Carbonic anhydrase, Alcohol dehydrogenase, Alkaline phosphatase
• Selenium → Glutathione peroxidase

Additional Sulphur Facts

Wool contains 4% sulphur; human hair keratin contains 14% sulphur. Sulphur-containing hormones: Insulin, ADH/Vasopressin, Oxytocin.