iron
When a hemoglobin molecule is broken apart, the iron pigment is released. This is what is called the -"heme" part of the molecule.
The iron containing part of hemoglobin is the 'heme' molecule.
Iron Ion
The part of the blood that is responsible for carrying oxygen is hemoglobin. The hemoglobin binds to oxygen in the alveoli of the lungs. Then the hemoglobin releases the oxygen at the cells. The part of the hemoglobin molecule that is directly responsible for carrying the oxygen is the iron ion in the center of the molecule's structure. The iron ion changes from a Fe +2 ion to a Fe +3 when carrying the oxygen. Then the hemoglobin reaches the cell, the iron ion decomposes back to the more stable Fe +2 state, replacing the oxygen with a water molecule.
A portion of the heme group
The heme group within the hemoglobin molecule is what actually binds to the oxygen molecule. This process involves the iron atom within the heme group forming a reversible coordination bond with the oxygen molecule.
Hemoglobin is the protein in red blood cells that carries oxygen. It contains iron as one of its chief components.
Carbon dioxide primarily binds to the globin part of the hemoglobin molecule, specifically to specific amino acid residues within the globin chains. This binding forms carbaminohemoglobin and plays a role in the transport of carbon dioxide from tissues to the lungs for elimination.
The iron molecule (that's the hemo- in hemoglobin) gains and/or loses an oxygen molecule. The protein part (that's the globin) changes shape a bit. Both changes are very reversible and requires little energy.
Iron is part of the hemoglobin molecule, which helps carry oxygen around the body through the bloodstream
hemoglobin
Heme part of hemoglobin is pigmented part.