Cough (Definition) 1  Coughing is an important way to keep your throat and airways clear. 2  Congestion refers to any situation of backup of fluid.. 3  Pain in the back is a symptom that can be due to a number of causes including musculoskeletal or neurological problems or due to problems with the internal organs.
A2A: Quickly speaking, the heme group contains the famous iron ion that is in hemoglobin, that binds to and carries oxygen. The iron atom has a very strong covalent bond with the globular protein on the proximal histidine of the protein (the F8 histidine residue), on histidine's imidazole ring. Even with this strong covalent bond, the iron still has the ability to bind with oxygen via a dipolar or coordinate covalent bond. That is the electrostatic bond that hemoglobin is involved in, not the one that binds heme to the globin proteins in the first place. So the iron atom is not only involved in keeping the heme group attached to the globin proteins, but it is the functional oxygen-carrying component of the hemoglobin molecule.
The iron atom in heme binds to the 4 nitrogen atoms in the centre of the porphyrin ring, but this leaves two free bonding sites for the iron, one on either side of the heme plane. The heme group is located in a crevice in the myoglobin molecule, surrounded by non-polar residues except for two polar histidines.