Iron Metabolism Flashcards

Flashcards about Iron Metabolism

What is the role of iron in the porphyrin ring of heme?

Stabilizes oxyhemoglobin and plays a role in oxygen transport

In what oxidation states does iron participate in oxidation-reduction reactions?

Ferrous (Fe2+) and Ferric (Fe3+)

What are cytochromes?

Enzymes that act as electron transfer agents in oxidation-reduction reactions

What is the role of peroxidase and catalase?

To decompose peroxides

What are the two forms of storage iron?

Ferritin and Hemosiderin

What is Ferritin?

A protein shell surrounding an iron core, found in nearly all cells

What is Hemosiderin?

Insoluble in aqueous solutions and found predominately in cells of the liver, spleen and bone marrow

What is Myoglobin?

The oxygen carrier in muscle cells.

What is Transferrin?

Apotransferrin + Fe3+ complex

What is the primary site of iron absorption?

Small intestine, primarily the duodenum and the jejunum

In what state must iron be in to be absorbed into the intestinal cells?

Ferrous (Fe2+)

Name reducing agents that reduce ferric (Fe3+) iron to ferrous (Fe2+).

Vitamin C or ferric reductases

What are the two forms of iron absorbed from the intestinal tract?

Heme iron and Non-Heme iron

How is iron present in the intestinal mucosal cell?

Result of passive diffusion

Once iron enters the mucosal cell in the ferrous (Fe2+) state, what happens?

Iron is quickly oxidized to the ferric (Fe3+) state and bound to a carrier molecule.

What is the labile storage pool of iron?

Located in the mucosal cell subject to loss at any time; iron can be distributed to apotransferrin from this pool

What organ produces apotransferrin?

The liver

Explain the first steop of cell uptake of iron

Iron-loaded transferrin (Fe2-Tf) binds to transferrin receptors (TfR) on the cell surface

How must iron coming from ferritin be processed for release into the bloodstream?

From ferritin, it must first be reduced to the ferrous (Fe2+) form.

What is hemosiderin?

Ferritin that has lost some of its apoferritin coating

Define Iron Deficiency

Diminished total body iron content

List causes for increased serum iron

Increased erythrocyte destruction, decreased utilization of iron, increased release from stores and defective iron storage

What is Grade I Iron Deficiency?

Decreased total body iron but enough to support all hemoglobin synthesis

What is Grade II Iron Deficiency?

Iron supply to erythropoiesis becomes insufficient resulting in iron-deficient erythropoiesis

What is Grade III Iron Deficiency?

Iron supply is no longer able to maintain normal hemoglobin levels (ex: iron deficiency anemia)

What causes abnormal iron metabolism in chronic disease?

Blockage of mobilization of iron storage sites in chronic inflammatory infections or neoplastic disorders.

What is the classic triad of symptoms for Hemochromatosis?

Bronzing of skin, cirrhosis, and diabetes

What is Pernicious Anemia?

Failure of gastric mucosa to produce intrinsic factor, which results in a lack of or greatly reduced B12 absorption

What does Serum Iron measure?

Measures iron that is bound to transferrin

What is TIBC?

Measurement of the total amount of iron that transferrin can bind; assess transferrin levels.

What is UIBC?

Amount of additional iron which transferrin can bind, above that which is already bound.

How is Percent Saturation calculated?

(serum iron/TIBC) X 100

What does Serum Ferritin measure?

Measure of the small amount of ferritin released directly into serum from iron storage cells

Why is Zinc Protoporphyrin (ZPP) measured instead of free erythrocyte protoporphyrin (FEP)?

When there is no iron to bind with protoporphyrin, zinc will take its place

When determining serum transferrin receptors (TfR), what is this useful in doing?

Determining the pathophysiology of anemia and detecting functional Fe deficiency