Circulating erythrocytes live for about 120 days. As a RBC ages:

1- The membrane becomes less flexible.

2- The concentration of cellular hemoglobin increases.

3- Enzyme activity, particularly glycolysis, diminishes.

Without key organelles such as a nucleus or ribosomes, RBCs cannot repair themselves.

Many RBCs die in the spleen, where they become trapped in narrow channels, broken up and destroyed. Haemolysis refers to the rupture of RBCs, where haemoglobin is released leaving empty plasma membranes which are easily digested by cells known as macrophages in the liver and spleen.

The Hb is then further broken down into its different components and either recycled in the body for further use or disposed of.

The resulting components are heme (iron, protoporphyrin), and globin.

1. Iron is transported in the plasma by transferrin to be manufacture of new hamoglobin or to be stored as ferritin in BM.

2. Globin is catabolized in liver into its constituent amino acids and enter the circulating amino acid pool, later used for protein synthesis.

3. The porphyrin ring is broken ------------ Biliverdin ------------Bilirubin ------ released into blood ------------- binds to albumin --------- enter liver --------- binds with glucuronic acid ( to form a bile salt) ----------- relesased into small intestine ------------- acted upon by bacteria --------------

Will either:

a. Stay in DIG tract ------- STERCOBILINOGEN (brown/orange color of Feces).

b. Go to Kidney ---------- UROBILINOGEN (amber color of urine).