Symbol: Cu. A metal element, atomic number 29, atomic weight 63.55, essential in trace amounts for growth. It is found in the enzyme cytochrome c oxidase, which is thought to catalyse the transfer of electrons from cytochrome a3 to oxygen in respiration. In this reaction the two copper atoms of the molecule undergo transition from the cupric, Cu (II), to the cuprous, Cu(I) state. Copper also plays a role in photosynthetic electron transport, being found in the protein *plastocyanin
Copper deficiency leads to chlorosis, which suggests the element may also play a role in the synthesis of chlorophyll.