The document discusses iron absorption from the gastrointestinal tract. Iron exists in foods and in the gut in forms such as Fe2+, Fe3+, heme, and non-heme iron. Factors like bile, sugars, citrates, lactate and amino acids can help convert forms like Fe3+ to Fe2+ to aid absorption. Apotransferrin in the blood binds to Fe2+ to form transferrin which transports iron through the body. Absorption rates vary from about 0.5-1 mg/day in adult males to 3-4 mg/day in pregnant females. Vitamin C, citrate and alcohol can increase absorption while plant compounds like phytates and tannins inhibit absorption.

2. Iron Absorption From GIT
By: Abdullah Bin Khurram

3. Fe2+
Fe3+
Haeme
Food Iron
sugars citrates
Lactate
Amino
acids

4. Bile
Apotransferrin

5. Apotransferrin Fe2+
Transferrin

6. The receptor molecule is a transmembrane homodimer linked by disulfide bonds. An
acyl group attached to the cytoplasmic tail of the molecule anchors the assembly to the
plasma membrane.
Disluphide bond
Acyl group
Transferrin

9. Oxidation
Oxidation
Hemin enters the mucosal cells

10. Mucosal Cell
• Hemin is cleaved to
release iron
• Haeme may be
absorbed as such into
the blood, where it is
bound by
HEMOPEXIN

11. • Only 5 - 10% of dietary iron is absorbed, because of the “Ferritin
Barrier”
• Rate of Iron absorption:
– Adult male: abt 0.5 – 1 mg per day
– Menstruating Female abt 1 – 2 mg per day
– Pregnant female abt 3 – 4 mg per day
0
1
2
3
4
Adult Male Menstruating
Female
Pregnant
Female
Min Value
Max Vale

12. • They vary as follows as per rate of absorption:

13. Factors increasing iron Uptake
• Vitamin C (aids Fe3+
→ Fe2+
)
• Citrate
• Alcohol
• Fructose

14. Inhibitors of Iron Absorption
• Plant phytates
– Tightly bind to iron and prevent its absorption
– Present in cereals
• Plant tanins
• Phosphates and oxalates
• Calcium
• Pancreatic juice (Ganong)