We ingest dietary iron in the form of either as free Fe or as haem bound Fe
The efficiency of absorption varies & is between 5-25% only☹️
It also depends on total body Fe stores
We cannot expel iron by metabolism: then what's the way❓(1) We depend on slow losses through cell sloughing, menstruation, bleeding etc (2) We absorb only what we want
Fe is absorbed through duodenal & jejunal mucosa
If it's free Fe, it attaches itself to a specific receptor ( it's expression depends on the total body Fe stores) on the apical membrane of the cell. Fe is absorbed by active transport.
If haem-bound Fe, it enters the cell by pinocytosis, and inside the cell, haem is broken down
Here it binds with apoferritin to form ferritin, which is the intracellular storage form.
When required, Fe is released into the plasma. Here it binds with the transport molecule beta-transferrin ( it's expression is also dependent on total body Fe store)
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