Iron physiology Flashcards

1
Q

what is Ferrous iron and can you absorb it?

A

Fe2+
-absorbable iron

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2
Q

What is Ferric iron and can you absorb it?

A

Fe3+
-not absorbable

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3
Q

what form is iron in when digested?

A

Fe3+
-ferric
-not absorbable

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4
Q

where does iron absorption occur?

A

duodenum

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5
Q

what enhances absorption of iron?

A

-Ascorbic acid
-Alcohol
-Haem (from meat) iron easier to absorb than non haem

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6
Q

what inhibits absorption of iron?

A

-Calcium
-Tannins e.g. tea
-Phytates e.g. cereals, bran, nuts and seeds

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7
Q

where are Duodenal cytochrome B found?

A

luminal surface of duodenum

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8
Q

role of Duodenal cytochrome B?

A

reduced ferric (Fe3+) iron to ferrous (Fe2+) form

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9
Q

what transports ferrous iron into the duodenal erythrocyte?

A

DMT-1
-divalent metal transporter 1

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10
Q

role of ferroportin?

A

-facilitates iron export from the enterocyte
-passed on to transferrin to transport elsewhere

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11
Q

what is the major negative regulator of iron uptake?

A

Hepcidin

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12
Q

where is hepcidin produced?

A

-in the liver

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13
Q

how does Hepcidin work?

A

-Major negative regulator of iron uptake
-Produced in liver in response to increased iron load and inflammation
-Bind to ferroportin and causes its degredation
-Iron therefore ‘trapped’ in duodenal cells and macrophages
-Hepcidin levels decrease when iron deficient

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14
Q

what is apotransferrin?

A

transferrin not bound to anything

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15
Q

explain the mechanism of how non haem iron is taken up?

A
  1. Iron digested and presents in Fe3+
  2. Fe3+ converted to Fe2+ by duodenal cytochrome B on the lumen of duodenum
  3. Fe2+ and H+ transported into the duodenal enterocyte by DMV-1 (divalent metal transporter 1)
  4. Some iron is stored as ferritin
  5. Fe2+ leaves the cell through ferroportin
  6. Hephaestin converts Fe2+ to Fe3+ (Iron needs to be in Fe3+ form to travel)
  7. Transferrin binds to Fe3+ and allows it to travel through the body

75% transferrin goes to bone marrow for erythropoieisis, they bind to tranferrin receptors on RBC

10-20% taken to the liver and stored as ferritin in the liver

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16
Q

how is haem iron taken up?

A

directly by a haemoglobin transporter