- Vitamin B-12 (Cobalamin) is a complex molecule containing a cobalt ion coordinated within a corrin ring. - Hemoglobin is a protein in red blood cells that transports oxygen; each heme group within hemoglobin contains an iron atom. - Chlorophyll is the primary pigment in plants responsible for photosynthesis; it has a porphyrin ring structure with a central magnesium ion. - Chalcopyrite (CuFeS2) is a copper iron sulfide mineral and is the most abundant copper ore mineral. It contains copper and iron.