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Globular proteins have no systematic structures. There may be single chains, two or more chains which interact in the usual ways or there may be portions of the chains with helical structures, pleated structures, or completely random structures. Globular proteins are relatively spherical in shape as the name implies. Common globular proteins include egg albumin, hemoglobin, myoglobin, insulin, serum globulins in blood, and many enzymes. Myoglobin and hemoglobin are much alike in their action toward oxygen. All body cells require oxygen for metabolism, but unfortunately, oxygen is non-polar and not soluble in the aqueous blood. The problem then becomes, how do you get oxygen to the tissue cells? Hemoglobin is used to transport oxygen in the blood in red blood cells to tissue cells where it is used directly. Myoglobin is present in skeletal muscles as an extra storage protein to enable muscles cells to have a readily available supply of oxygen. Heme: Hemoglobin and myoglobin both a have group called “heme“, which is at the heart of the protein structure. The molecular structure is shown in the left graphic. It is made from a a series of nitrogen five member cyclic rings, that are further joined to each other by more rings. At the center of the heme group is the iron 2 metal ion. The nitrogen atoms bind to the iron ion through what are called coordinate covalent bonds. This means that ,unlike normal covalent bonds where each atom contributes one electron for the bond, that the nitrogen contributes both electrons for the coordinate covalent bond. The oxygen molecule will ultimately bind to this iron ion also using a coordinate covalent bond. Problems: The oxygenated form of hemoglobin is together by which type of bonding? A) H2-Bonding B) Covalent bond C) Metallic bond D) Salt bridges What prosthetic group is present in the hemoglobin? A) Heme B) Globin C) Phosphoric acid D) Lipoprotein #prosthetic #hemoglobin #heme #globin #blood #RBC #redBloodCell #protein #polypeptide
