Biological Role
Copper proteins have diverse roles in biological electron transport and oxygen transportation, processes that exploit the easy interconversion of Cu(I) and Cu(II). The biological role for copper commenced with the appearance of oxygen in earth's atmosphere. The protein hemocyanin is the oxygen carrier in most mollusks and some arthropods such as the horseshoe crab (Limulus polyphemus). Because hemocyanin is blue, these organisms have blue blood, not the red blood found in organisms that rely on hemoglobin for this purpose. Structurally related to hemocyanin are the laccases and tyrosinases. Instead of reversibly binding oxygen, these proteins hydroxylate substrates, illustrated by their role in the formation of lacquers.
Copper is also a component of other proteins associated with the processing of oxygen. In cytochrome c oxidase, which is required for aerobic respiration, copper and iron cooperate in the reduction of oxygen. Copper is also found in many superoxide dismutases, proteins that catalyze the decomposition of superoxides, by converting it (by disproportionation) to oxygen and hydrogen peroxide:
- 2 HO2 → H2O2 + O2
Several copper proteins, such as the "blue copper proteins", do not interact directly with substrates, hence they are not enzymes. These proteins relay electrons by the process called electron transfer.
Read more about this topic: Copper
Famous quotes containing the words biological and/or role:
“I am fifty-two years of age. I am a bishop in the Anglican Church, and a few people might be constrained to say that I was reasonably responsible. In the land of my birth I cannot vote, whereas a young person of eighteen can vote. And why? Because he or she possesses that wonderful biological attribute—a white skin.”
—Desmond Tutu (b. 1931)
“This [new] period of parenting is an intense one. Never will we know such responsibility, such productive and hard work, such potential for isolation in the caretaking role and such intimacy and close involvement in the growth and development of another human being.”
—Joan Sheingold Ditzion and Dennie Palmer (20th century)