Bioinorganic chemistry examines the roles of inorganic elements in biological processes. Metal ions can have structural or catalytic roles, often present at the active site of metalloproteins. The reactivity of metalloproteins is defined by the metal's electronic structure and oxidation state, which are determined by its coordination environment and protein architecture. Transition metals like iron, zinc, and copper are essential nutrient metals that serve catalytic roles in redox reactions and oxygen transport/storage in proteins like hemoglobin, myoglobin, and chlorophyll. Metalloenzymes utilize transition metals at their active sites to catalyze reactions like oxidation, reduction, and nitrogen fixation.