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:
“Man’s biological weakness is the condition of human culture.”
—Erich Fromm (1900–1980)
“The role of the writer is not simply to arrange Being according to his own lights; he must also serve as a medium to Being and remain open to its often unfathomable dictates. This is the only way the work can transcend its creator and radiate its meaning further than the author himself can see or perceive.”
—Václav Havel (b. 1936)