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Questions and Answers
Which of the following is NOT a facilitator of iron absorption?
Which of the following is NOT a facilitator of iron absorption?
Which of the following is the primary storage form of iron in the body?
Which of the following is the primary storage form of iron in the body?
What is the primary form of iron that can be absorbed by the intestines?
What is the primary form of iron that can be absorbed by the intestines?
What is the function of Hephaestin in iron metabolism?
What is the function of Hephaestin in iron metabolism?
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What is the role of ferric reductase (Dcytb1) in iron metabolism?
What is the role of ferric reductase (Dcytb1) in iron metabolism?
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What is the difference between transferrin and apotransferrin?
What is the difference between transferrin and apotransferrin?
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What is the primary function of divalent metal transporter 1 (Dmt1) in iron metabolism?
What is the primary function of divalent metal transporter 1 (Dmt1) in iron metabolism?
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What is the role of ferroportin in iron metabolism?
What is the role of ferroportin in iron metabolism?
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How many iron ions can a single transferrin molecule bind?
How many iron ions can a single transferrin molecule bind?
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Which of the following is NOT a function of iron in the body?
Which of the following is NOT a function of iron in the body?
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What happens to transferrin levels when iron stores become low?
What happens to transferrin levels when iron stores become low?
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What is the difference between ferritin and hemosiderin?
What is the difference between ferritin and hemosiderin?
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What is the main difference in absorption between heme iron and non-heme iron?
What is the main difference in absorption between heme iron and non-heme iron?
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Where is ferritin primarily stored in the body?
Where is ferritin primarily stored in the body?
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Which of these is NOT a test used to assess iron levels in the blood?
Which of these is NOT a test used to assess iron levels in the blood?
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In which condition would you expect to see an increased total iron-binding capacity (TIBC)?
In which condition would you expect to see an increased total iron-binding capacity (TIBC)?
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What is the relationship between Total Iron-Binding Capacity (TIBC) and Transferrin?
What is the relationship between Total Iron-Binding Capacity (TIBC) and Transferrin?
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How is TIBC calculated?
How is TIBC calculated?
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In cases of iron deficiency anemia, what would you expect to see in terms of serum iron and TIBC levels?
In cases of iron deficiency anemia, what would you expect to see in terms of serum iron and TIBC levels?
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Which of the following is NOT a cause of iron overload (Hemosiderosis)?
Which of the following is NOT a cause of iron overload (Hemosiderosis)?
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Which of the following laboratory findings is characteristic of iron overload (Hemochromatosis)?
Which of the following laboratory findings is characteristic of iron overload (Hemochromatosis)?
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Study Notes
Iron Metabolism Overview
- Iron is a trace element essential for proper growth, development, and physiology.
- It's the most important trace element.
Distribution of Iron in the Body
- 66% is in hemoglobin
- 6% is in myoglobin
- <1% is in Heme enzymes.
- 26% is in transport and storage forms.
- <1% is in iron-sulfur clusters
Biochemical Functions of Iron
- Essential for hemoglobin and myoglobin synthesis.
- Crucial for cytochromes (electron transport chain).
- Necessary for peroxidase synthesis (phagocytosis).
- Important for synthesizing non-heme iron compounds like succinate dehydrogenase and iron-sulfur proteins.
- Associated with effective immune function.
Iron Requirements
- Daily requirement is 15-20 mg.
- Only 2 mg of iron is normally absorbed.
Iron Sources
- Best sources: meat, eggs, salmon, tuna, liver, poultry.
- Lesser amounts are in dark leafy greens, fruits (apples), and whole grains.
- Animal sources are better absorbed than plant sources.
Iron Absorption
- Factors influencing absorption:
- Facilitators: reducing agents (ascorbic acid, citrate), hydrochloric acid (HCl) in the stomach.
- Inhibitors: phytates (in cereals), oxalates, tannic acid, antacids.
- Competitors: calcium, manganese, zinc
Iron Metabolism (Cellular Level)
- Non-heme iron is reduced to ferrous form (Fe2+) for absorption.
- This is facilitated by ferric reductase enzymes like Dcytb1.
- It is then transported into the enterocyte using DMT1.
- Some iron is stored as ferritin within the enterocyte.
- Hephaestin converts Fe2+ to Fe3+ at the basal surface.
- Fe3+ binds to transferrin for transport out of the enterocyte.
Iron Storage Forms
- Transferrin: protein carrier in circulation (e.g., from gut to bone marrow).
- Apotransferrin: transferrin not bound to iron.
- Ferritin: storage form in hepatocytes and enterocytes.
- Hemosiderin: aggregated ferritin overloaded with iron.
Iron Transport
- Iron is carried in Fe3+ form bound to transferrin.
- Transferrin is a plasma glycoprotein synthesized in the liver; it can carry two Fe3+ ions.
- Normally, 1/3 of circulating transferrin is fully saturated with iron.
- The transferrin-iron complex enters cells via specific receptors, and iron is released for metabolic functions.
Iron Levels in Blood
- Measuring iron and iron-binding capacity is crucial to diagnose deficiencies or overload.
- Serum iron alone isn't conclusive.
- Total Iron Binding Capacity (TIBC), and unsaturated iron-binding capacity (UIBC) are necessary tests.
Ferritin
- Primary iron storage protein in intestinal mucosa, liver, spleen, and bone marrow.
- Apoferritin can bind up to 4000 iron atoms to form ferritin.
- Has the ability to gain and release iron based on body's iron stores.
Hemosiderin
- Formed by partial degradation of ferritin due to iron overload.
- Found in liver, spleen, and bone marrow.
- Accumulates as brown aggregates in tissues when iron levels are high.
Iron Disorders
- Iron deficiency anemia: Causes: inadequate intake, impaired absorption, chronic blood loss, increased demand. Lab findings: decreased serum iron, increased TIBC.
- Iron overload (Hemosiderosis/Hemochromatosis): Causes: repeated attacks of hemolysis, repeated blood transfusions. Lab findings: increased serum iron, decreased TIBC, and increased ferritin.
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Description
Test your knowledge on iron metabolism, its essential role in the body, and how it is distributed among various components. This quiz covers the biochemical functions of iron, daily requirements, and dietary sources necessary for optimal health. Assess your understanding of this crucial trace element with engaging questions.
