Lecture 22; Minerals Flashcards
What are the major iron-containing and iron-binding proteins, and their functions?
Haemoglobin and myoglobin -> Oxygen transport
Cytochrome oxidase->Electron transport
Cytochrome P450 -> Metabolism Fa….
Ribonucelotide reductase -> DNA synthesis
In brief describe iron homeostasis;
Tightly regulated thus not much is needed in diet.
Describe iron bioavailability;
Iron bioavailability is low but variable depending on
- Physiological factors
- Dietary factors
Describe iron recycling;
- Transferrin carries iron in blood
- Some delivered to myoglobin, some to bone marrow for erythrpoeisis or storage
- RBC have iron, some lost in bleeding i.e mensturation
- liver (heamolysis)
- Some iron lost in urine, sweat
Describe iron absorption;
- Mucosal cells in the intestine store excess iron in mucosal ferritin
= If body does not need iron it is lost in shed intestinal cells
= If body does need iron then; Mucosal ferritin releases iron to mucosal ferritin to mucosal transferrin
What are the two types of iron?
Heme (animal only) (well absorbed, less of daily iron)
Non-heme (plant and animal) (not well absorbed, most of daily iron)
Where does iron absorption occur?
Duodenum and proximal jejunum
Describe heme iron absorption?
Heme, part of heamoglobin enters enterocyte through an unidentified transport protein. Iron is removed from the heamoglobin. (Heme oxygenase). Ferrous (reduced) iron is added to the pool in the enterocyte. Stored with ferritin if body doesnt need iron.
Notes for if body needs iron are later in questions
Describe non-heme iron absorption;
Non-heme iron is reduced (either by HCl or luminal reducing enzyme) (ferric -> ferrous).
Transported into the cell by DMT1.
Stored with ferritin in cell if not needed.
What happens to ferrous iron in the enterocyte if it is needed by the body?
Transported out of the cell by FERROPORTIN
Hephaestin oxidises the iron to FE3
Binds transferrin and is transported around the body
What is the master regulator of iron?
Hepcidin
What is Hepcidin and what does it do?
Hepatic Bacteriocidal Protein
- Inactivates Ferroportin (stops iron getting out of gut cell)
- Leads to decreased gut iron absorption
What factors enhance non-heme iron absorption?
- MFP factor
- Vit C
- Citric acid
- Lactic acid
- HCl in stomach
- Sugars
What factor inhibit non-heme iron absorption?
- Phytates
- Fibres
- Oxalates
- Calcium
- Phosphorus
- Polyphenols
- Tannins
What else can add to iron absorption, not in food?
- Iron contamination, cooking with iron pots
- Iron supplements (non-heme)
- Iron fortification
