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Introduction

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High-Yield Terms

  • Ferrous iron: iron with an oxidation state of +2 (Fe2+ or Fe[II])

  • Ferric iron: iron with an oxidation state of +3 (Fe3+ of Fe[III])

  • Cuprous copper: copper with an oxidation state of +1 (Cu1+ or Cu[I])

  • Cupric copper: copper with an oxidation state of +2 (Cu2+ or Cu[II])

  • Ferroxidase: any of a class of enzyme that oxidizes ferrous (Fe2+) iron to ferric (Fe3+) iron

  • Ferrireductase: any of a class of enzyme that reduces ferric (Fe3+) iron to ferrous (Fe2+) iron

  • Reticuloendothelial cells: comprise phagocytic cells located in different organs of the body, responsible for engulfing, bacteria, viruses, other foreign substances, and abnormal body cells

  • Hemosiderin: an intracellular complex of iron, ferritin, denatured ferritin and other material, most commonly found in macrophages, accumulates in conditions of hemorrhage and iron excess

  • Ceruloplasmin: is a ferroxidase that is also a major copper-requiring protein of the blood

  • Metallothioneins: a family of cysteine-rich proteins that bind a variety of metals and are thought to provide protection against metal toxicities

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Role of Iron

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Iron serves numerous important functions in the body relating to the metabolism of oxygen, not the least of which is its role in hemoglobin transport of oxygen. Within the body iron exists in 2 oxidation states: ferrous (Fe2+) or ferric (Fe3+). Because iron has an affinity for electronegative atoms such as oxygen, nitrogen, and sulfur, these atoms are found at the heart of the iron-binding centers of macromolecules.

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Under conditions of neutral or alkaline pH, iron is found in the Fe3+ state and at acidic pH the Fe2+ state is favored. When in the Fe3+ state, iron will form large complexes with anions, water, and peroxides. These large complexes have poor solubility and upon their aggregation lead to pathological consequences. In addition, iron can bind to and interfere with the structure and function of various macromolecules. For this reason the body must protect itself against the deleterious effects of iron. This is the role served by numerous iron-binding and transport proteins.

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Aside from its importance as the prosthetic group of hemoglobin and a number of enzymes (eg, redox cytochromes and the P450 class of detoxifying cytochromes), heme is important because a number of genetic disease states are associated with deficiencies of the enzymes used in its biosynthesis. Some of these disorders are readily diagnosed because they cause δ-aminolevulinic acid (ALA) and other abnormally colored heme intermediates to appear in the circulation, the urine, and in other tissues such as teeth and bones.

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Iron Metabolism

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Iron is associated with proteins either by incorporation into protoporphyrin IX (forming heme) or by binding to other ligands. There are a number of heme containing proteins involved in the transport of oxygen (hemoglobin), oxygen storage (myoglobin), and enzyme catalysis ...

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