- The heme group contains an iron molecule in the
reduced or ferrous form (Fe2+).
In this form, iron can combine with oxygen, by sharing an electron, to form
oxyhemoglobin. When oxyhemoglobin releases oxygen to the tissues, the iron
molecule is restored to its original ferrous state.
Hemoglobin can accept and transport
oxygen only when the iron atom is in its ferrous form. (think
'ferrous' has an O and can accept and transport O2)
- When hemoglobin becomes oxidized (due to normal exposure to oxidant stress
or other causes (below)), it is converted to the
ferric state (Fe3+) or
lacks the electron that is needed to form a bond with oxygen and, thus,
is incapable of oxygen transport.
Because red blood cells are continuously exposed to various oxidant stresses,
blood normally contains approximately 1%
- it can then no longer transport
oxygen or CO2
- a drop of blood exposed to air has a chocolate hue
- exposure to certain drug or
chemicals (nitrates or nitrites i.e. a complication of NO therapy (ie. in treatment of PPHN)
- local anesthetics ie topical benzocaine in Anbesol
NADH-methemoglobin reductase deficiency or hemoglobin M disease
- treat with