Iron Absorption From GIT

By: Abdullah Bin Khurram

Fe2+ Fe3+

Haeme

Food Iron

sugars citrates

Lactate

Aminoacids

Bile

Apotransferrin

Apotransferrin Fe2+Transferrin

 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

Oxidation

Oxidation

Hemin enters the mucosal cells

Mucosal Cell

• Hemin is cleaved to release iron

• Haeme may be absorbed as such into the blood, where it is bound by HEMOPEXIN

• 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 MenstruatingFemale

PregnantFemale

Min Value

Max Vale

• They vary as follows as per rate of absorption:

Factors increasing iron Uptake

• Vitamin C (aids Fe3+ → Fe2+)

• Citrate

• Alcohol

• Fructose

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)