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1. C R I T I C A L E L E M E N T I N T H E F U N C T I O N O F
A L L C E L L S
I R O N I S R E Q U I R E D B Y E V E R Y C E L L
IRON METABOLISM
1
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2. Ferrous (Fe2+) and ferric (Fe3+) forms
2
 Iron can interconvert
 Makes it a useful component of
 Oxygen-binding molecules (i.e., hemoglobin and
myoglobin)
 Cytochromes
 Many enzymes
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3. Free iron
3
 Highly toxic
 Can generate free radicals
 Catalyze the conversion of hydrogen peroxide to free-
radical ions
 Free-radical ions attack cellular membranes,
proteins, and DNA
 Proteins bind iron to reduce this toxic effect
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4. Main role of iron
4
 Carry oxygen
 Iron is part of the heme protein of hemoglobin
 Iron deficiency
 Hemoglobin synthesis is impaired
 Anemia - reduced oxygen delivery to tissue
 Iron overload
 Widespread organ damage and death
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5. How does iron circulate in blood?
5
 Bound to plasma transferrin
 Each transferrin molecule binds two atoms of
ferric iron
 Normally one-third saturated (35 %)
 Responsible for TIBC
 250-370 microgram/dl
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6. How do cells store iron?
6
 In the form of ferritin
 Up to 4500 atoms of iron can be stored in a
single ferritin molecule
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7. Storage form of iron (500-1500 mg)
7
 Iron is stored in
 Reticuloendothelial cells
 Hepatocytes
 Skeletal muscle cells
 Two-thirds stored as ferritin
 One-third as haemosiderin
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8. Reticuloendothelial macrophages
8
 Degrade hemoglobin in old erythrocytes
 Give it to transferrin for delivery to cells
 Provide most of the usable iron
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9. Pathway of internal iron exchange
9
RBC
RE
CELLS
PLASMA
Tf
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10. Unidirectional flow
10
 From plasma transferrin to the RBC to the
macrophage (RE cells) and back to plasma
transferrin
 80% of iron passing through the plasma
transferrin pool
 Recycled from broken-down red cells
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11. Storage iron
11
 Macrophages
 Liver
 Main site of storage
 Bone marrow
 Spleen
 Derived almost entirely from phagocytosis of
senescent erythrocytes or defective
developing red cells
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12. IRON CYCLE
12
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13. SUMMARY
13
 80% of iron passing through the plasma
transferrin pool is recycled from broken-
down red cells
 Storage iron in the macrophages of the liver,
bone marrow, and spleen is derived almost
entirely from phagocytosis of senescent
erythrocytes or defective developing red cells
 Macrophage takes up little iron from plasma
transferrin
 Hepatocyte may either donate iron to or
receive iron from plasma transferrin
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14. Most of the iron bound to transferrin comes from
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A. Iron absorbed by the intestine
B. Macrophages
C. Ferritin
D. Reticulocytes
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15. ANSWER
15
 B – Macrophages
 Most of the iron bound to transferrin comes from
macrophages in the reticuloendothelial system and
not from iron absorbed by the intestine
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