Iron Utilization and Iron Cycle

Question 1

Enterocyte

Answer 1

takes in Fe2+ via DMTI transporter
Fe2+ Pool can form ferritin or get shipped out of enterocyte via Ferroportin
In cytoplasm Fe2+ gets converted into Fe3+ via hephaestin
Apo-transferrin binds to Fe3+ to become transferrin to carry iron molecules

Question 2

Erythroblast

Answer 2

takes in Fe via TfR (transferrin receptor) and phagocytoses transferrin
Fe3+ leaves phagosome in cytoplasm and transferrin gets recycled
Fe3+ joins the Fe2+ pool where it can get converted to hemoglobin

Question 3

Macrophage

Answer 3

Takes in Fe via phagocytosed RBC or TfR binding transferrin
Iron from RBC and transferrin joins Fe2+ pool where it is converted to Ferritin or shuttled out of cell via ferroportin
Outside of cell Fe2+ is converted to Fe3+ via ceruloplasmin

Question 4

Hepatocyte

Answer 4

Takes in Fe via TfR
Cell translates apo-transferrin for circulation
Fe2+ from transferrin joins Fe2+ pool where it can be used to make ferritin
Fe2+ is shipped out of cell via ferroportin
In cyto Fe2+ to Fe3+ by ceruloplasmin

Question 5

What does apo-transferrin bind?

What is the difference between apo-transferrin and transferrin?

Answer 5

Apo-transferrin binds to Fe3+ (ferric) where it then becomes transferrin

Question 6

Main Regulator molecule of iron

Answer 6

hepcidin

Indicates that iron levels are full

Question 7

Hepcidin action

Answer 7

removes ferroportin from hepatocyte, macrophage and enterocyte not allowing it to pump out anymore Fe2+

Question 8

High Serum Iron effect on enterocyte

Answer 8

Fe bound to transferrin binds to TfR expressed on enterocyte and adds Fe2+ to Fe2+ pool.
High Fe2+ is converted to Fe3+ where it activates IRP. IRP activates DMT1-mRNA-IRE which inactivates DMT1 transporter

Question 9

High serum iron on erythroblast

Answer 9

Increaesed Fe2+ in pool converts to Fe3+
Fe3+ binds to IRP
IRP activates TfR mRNA-IRE which inactivates TfR from associating with membrane

Question 10

High serums iron on macrophage

Answer 10

Increased Fe2+ in pool converts to Fe3+
Fe3+ binds to IRP
IRP activates Apoferritin mRNA-IRE
Apoferritin promotes formation of Ferritin, thus macrophage stores iron during times of plenty.

Question 11

Levels during occult blood loss

Answer 11

Serum Iron Levels drop
Serum Ferritin Levels drop
Transferrin Levels = Total Iron Binding Capacity Increases (want to scoop up as much Iron as posisble)

Question 12

Levels during chronic Inflamation

Answer 12

Serum Iron Levels are low
Serum Ferritin levels are elevated
Total Iron Binding Capacity = High
Cytokines inhibit mobilization of iron from ferritin thus ferritin levels remain high.

Question 13

Total Iron Binding Capacity is an indirect measure of

Answer 13

Serum Tansferrin