The Essential Role of Iron in Biology

In the description of the prehistory of human technology, there are also three ages, namely the Stone Age, Bronze Age and Iron Age, defined by the materials out of which cutting tools and weapons were manufactured. This chapter discusses the importance of iron for biological systems, and presents an overview of the diversity of its role illustrated by the different classes of iron proteins. First, it considers haemoproteins into which an iron protoporphyrin is incorporated in different apo-proteins to produce O2 carriers, O2 activators. The chapter then considers proteins containing iron-sulphur clusters, many of which are involved in electron transfer. Finally, it talks about the non-haem, non-iron-sulphur, iron-containing proteins which include, in addition to enzymes, proteins of iron storage and transport. However, the downside was that molecular oxygen proved to be toxic, generating reactive oxygen species (ROS), reactive nitrogen species (RNS) and non-transferrin bound iron (NTBI) in the presence of iron.