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Questions and Answers
Which of the following are hypotheses that explain the control of intestinal iron absorption? (Select all that apply)
What is iron absorption regulated by according to the mucosal block hypothesis?
Apoferritin
The form in which iron is transferred to the liver for storage is known as ______.
transferrin
The active transport hypothesis suggests that iron absorption is not affected by anaerobic conditions.
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Match the following causes of anemia with their descriptions:
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Iron chelate hypothesis does not require metabolic energy for iron movement.
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What two requirements must an iron compound meet for replacement or supplemental therapy?
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Which iron compound is usually compared as a standard for other iron salts?
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Study Notes
Iron Absorption
- Three hypotheses explain regulation of Iron absorption:
- Mucosal Block Hypothesis: Iron absorption is regulated by the cell's apoferritin levels. Ferrous iron is absorbed into the mucosal cell, oxidized, and forms ferritin. Ferritin is then released into the blood and transported to the liver for storage and the bone marrow for heme synthesis.
- Active Transport Hypothesis: Iron absorption is regulated by an active transport system. This system requires ATP to move iron across the serosal membrane.
- Iron Chelate Hypothesis: Iron absorption is regulated by endogenous or exogenous ligands (chelating agents). These ligands bind to iron and form low molecular weight complexes that passively diffuse across the mucosal membrane. Iron is then either stored as ferritin or transferred to other ligands.
Iron Deficiency Anemia
- Iron deficiency anemia is a condition where circulating red blood cells are deficient in number or total hemoglobin content.
- This deficiency results in lower oxygen-carrying capacity of blood.
- Iron deficiency can be caused by:
- Excessive blood loss: bleeding ulcers, hemorrhaging, heavy menstrual flow.
- Blood destruction: hemolytic agents like drugs, infections, toxins, or defective hemoglobin like sickle cell anemia and thalassemia.
- Decreased blood formation: deficiencies in cobalamin, folic acid, pyridoxine, and iron, infections, renal insufficiency, malignancy, or marrow failure.
Iron Supplements
- Iron compounds used for supplemental therapy need to be:
- Biologically available
- Non-irritating
- Water-soluble ferrous sulfate is the standard reference for iron salts.
- Sustained release iron formulations are used to minimize the irritant properties of iron.
- Parenteral iron preparations are indicated for cases where oral iron is ineffective or contraindicated.
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Description
This quiz explores the mechanisms of iron absorption and the condition of iron deficiency anemia. It covers three hypotheses explaining the regulation of iron absorption and discusses the implications of iron deficiency on red blood cell counts and hemoglobin levels. Test your knowledge on this essential topic in human nutrition.
