Final answer:
The events of heme disposal occur in the following order: recycling of unused heme groups, inactivation of HCR kinase by excess hemin, breakdown of haemoglobin in the liver, metabolization of hemoglobin in states of oxidative stress, and binding of excess hemin to HCR kinase.
Step-by-step explanation:
The events of heme disposal can be placed in the following order:
Unused heme groups can be recycled and used in hemopoiesis, or can be converted into bilirubin and used to make bile in the liver. Iron ions can also be transferred to the protein ferritin for storage in the liver.
If heme accumulates in excess of globins, excess hemin (a heme precursor) binds & inactivates an HCR kinase: excess hemin.
The liver breaks down haemoglobin, creating metabolites that are added to bile as pigment (bilirubin and biliverdin).
In states of oxidative stress, all remaining glutathione is consumed. Enzymes and other proteins (including hemoglobin) are subsequently damaged by the oxidants, leading to electrolyte imbalance, membrane cross-bonding and phagocytosis and splenic sequestration of red blood cells. The hemoglobin is metabolized to bilirubin or excreted directly by the kidney.
By binding HCR kinase, excess hemin leaves GDP elF2 active. The GTP/GDP swap occurs & initiation continues until translation catches up with heme synthesis in the cell.