Final answer:
Selenium works primarily as a part of selenoproteins, most notably the enzyme glutathione peroxidase. It is an essential component of glutathione peroxidase and acts as a cofactor for essential enzymes in humans.
Step-by-step explanation:
Selenium works primarily as a part of selenoproteins, most notably the enzyme glutathione peroxidase. It is an essential component of glutathione peroxidase, an enzyme that catalyzes the conversion of reduced glutathione to its oxidized form. Selenium acts as a cofactor for essential enzymes in humans such as sulfite oxidase, xanthine oxidase, and aldehyde oxidase.