Question: What are the components of a functional heme group ?: 
 Options:  <1> Four molecules of bilirubin and one Fe3 +. <2> Four globins (2alpha + 2beta) and one Fe3 +. <3> One molecule of protoporphyrin and one Fe2 +. <4> One molecule of bilirubin and one Fe2 +. <5> Four globins (2alpha + 2beta) and one Fe2 +.
3