This post is the response to as students question on “Why is blood red” post.
Just like humans, red blood cells also get old, worn out and eventually die. But unlike humans, they live just about 100 – 120 days.
What really happens when red blood cells get old?
They lose their flexibility .They become rigid and fragile. Not just that, but the hemoglobin they contain begins to degenerate…
Because they can’t bend as much anymore, these old red cells become trapped, especially in the really small vessels. These really small vessels are found especially in the spleen (also the liver). This entrapment leads to fragmentation of the cell.
Macrophages ( big cells that eat up stuff) live in the spleen and when they encounter these old red blood cell, they engulf them and break down the Hemoglobin (which makes up 97% of the red blood cell) into Globin and Heme.
Do you remember what the Hemoglobin molecule looks like? It is made up of Heme and Globin:
What happens to HEME?
Heme is broken down. The Iron sitting on it is saved and stored to be used to make new red blood cells.
The remaining part of the Heme group is changed to a yellowish substance called Bilirubin which goes to the liver.
What Happens to the GLOBIN ?
The Globin part is broken down into Amino acids and released into the blood.
Here is a short video that explains everything: Life Cycle of the red blood Cell.
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