The erythrocytes have no nucleus, no endoplasmic reticulum and no mitochondria.
But there is some glucose oxidation which can produce ATP
This ATP is necessary for:
flexibility of the membrane
membrane ion transport
keep Fe in ferrous format otherwise; ferri-format = (methemoglobine) which is not suitable for oxygen binding.
The RBC test: All RBC’s (7 micron wide) will at one moment or another flow through the spleen. But the spleen consists of the narrowest capillaries (3 micron) in the body!
If the membrane of an old RBC is no longer flexible enough, it will break (=hemolysis) and the life of this RBC is terminated!
There is enough glucose and ATP to keep the RBC membrane flexible for about 120 days!
B.Destruction process of the RBC’s
In the spleen, the components of the old destroyed RBC’s in the spleen are recycled!
Fe => Transferrin => Ferritin.
In other words, the iron is stored and saved.
The globine is converted back into its amino acids which can be used for building other proteins.
The heme is processed in a very special manner:
The heme is converted, still in the spleen, first into biliverdin which is then converted into bilirubin.
This bilirubin then appears in the blood and is bound to the blood transport protein: albumin.
This bilirubin is called “free” or “indirect” bilirubin (depending on the book or the teacher or the country that you are being taught this).
This free or indirect bilirubin is then transported by the blood to the liver where it is conjugated.
This bilirubin is now called “conjugated” (!) or “direct” bilirubin. Whatever its name, this type of bilirubin is secreted into the bile.
The bile flows into the intestine, where the bilirubin is converted, by the intestinal bacteria, into urobilinogen.
This urobilinogen is absorbed by the blood and either goes back to the liver (to go back to the bile, to make a loop), or excreted by the kidney (as urobilin) or excreted via the stool (as stercobilin).
Important; the stercobilin gives the stool its characteristic brown colour. If you don’t have stercobilin, then the stool becomes pale like clay. This is an important diagnostic tool to discover diseases of the gall bladder or the bile duct!