Iron Flashcards
What are the functions of iron in the body?
Oxygen transport and storage
Role in enzyme function
- energy metabolism
- collagen formation
What are the different forms of available iron?
Haemoglobin
Myoglobin
Tissue iron
Transported iron - serum iron
What is myoglobin?
Oxygen-storing protein in muscle
What is tissue iron?
Iron in enzymes
What are the different forms of stored iron?
Ferritin
Haemosiderin
What is haemosiderin?
Iron in macrophages
How does ferritin react to water?
Soluble in water
How does haemosiderin react to water?
Insoluble in water
How does the requirement of iron change during pregnancy?
Iron requirement increases
Where does most iron in the body come from?
Recycling iron already within the body
How is iron stored in the liver?
Most of it as ferritin in hepatocytes
Small amount as haemosiderin in kupffer cells
Is iron excreted from the body?
No
no mechanism to excrete iron
How is iron lost from the body?
Small amount in
- skin
- gut cells
How much iron enters and leaves the body per day?
1-2mg
What are the different forms of iron in the diet?
Haem iron
Non-haem iron
What is haem iron?
Haem containing iron
What is the state of iron in haem iron?
Ferrous state - Fe2+
What foods contain haem iron?
Red meat
What is non-haem iron?
Iron on its own
What is the state of iron in non-haem iron?
Mainly ferric form - Fe3+
What foods contain non-haem iron?
Nuts
Grains
Eggs
How much iron is required in the diet?
10-15mg per day
What happens to non-haem iron in the stomach? What type of reaction is this?
Fe3+ —–> Fe2+
reduction
What facilitates the reduction of Fe3+ in the stomach?
Acid of stomach
H+
Where does iron absorption occur in the GI tract?
Duodenum
Upper jejunum
How does iron enter epithelial cells in the small intestine?
DMT1 transporter moves Fe2+ from intestinal lumen
into epithelial cell
Where is the DMT1 transporter located in the epithelial cell?
Apical domain
What happens to non-haem iron inside the epithelial cells?
Some is stored as ferritin
Rest is exported into the blood
How is iron moved from the epithelial cell to the blood?
Ferroportin transporter
Where is the ferroportin transporter located in the epithelial cell?
Basolateral domain
What do fetal enterocytes have additional receptors for?
Lactoferrin
What is the primary source of iron in babies-young children?
Lactoferrin
How does iron travel in the blood?
Bound to transferrin protein
How is iron taken up into body cells?
Iron-transferrin complex binds to transferrin receptor on cell
iron taken up into cell
Which body cell has the highest number of transferrin receptors? How does this affect their iron uptake?
Erythroid cells
take up most iron
What increases the absorption of non-haem iron?
Vit C
How does vit C increase absorpton of non-haem iron?
Increases acidity of stomach
more Fe3+ reduced to Fe2+
more Fe2+ absorbed
What decreases absorption of non-haem iron?
Antacids
Tea, coffee
What does the regulation of iron absorption depend on?
Dietary intake of iron
Body iron stores
Use of iron - erythropoiesis
What senses dietary levels of iron?
Villi in small intestine
What are the mechanisms regulating iron absorption?
Expression of transporters
Activity of transporters
What are some examples of molecules involved in regulating iron absorption?
Hepcidin
HFE protein
Where is hepcidin produced?
Liver
What increases the production of hepcidin?
Iron overload
What decreases the production of hepcidin?
High erythropoietic activity
What does hepcidin do? What are the effects?
Binds to ferroportin transporter
breaks it down
Prevents iron leaving epithelial cell into blood in small intestine
Prevents macrophages releasing iron
How is hepcidin removed from the body?
Excreted by kidneys
What regulates hepcidin?
HFE protein
Transferrin receptor
Inflammatory cytokines
