Podcast
Questions and Answers
What is the reactive center of the vitamin B12 molecule attached to in cyanocobalamin?
What is the reactive center of the vitamin B12 molecule attached to in cyanocobalamin?
How is vitamin B12 mainly combined in the stomach for absorption?
How is vitamin B12 mainly combined in the stomach for absorption?
What directs the endocytosis of the cubilin IF–B12 complex into the ileal cell for absorption?
What directs the endocytosis of the cubilin IF–B12 complex into the ileal cell for absorption?
Which protein is responsible for releasing dietary B12 for binding to intrinsic factor (IF) in the stomach?
Which protein is responsible for releasing dietary B12 for binding to intrinsic factor (IF) in the stomach?
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What is the maximum amount of B 12 that can be absorbed from a single oral dose via the IF–cubam mechanism?
What is the maximum amount of B 12 that can be absorbed from a single oral dose via the IF–cubam mechanism?
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What is the characteristic abnormality seen in the bone marrow erythroblasts in megaloblastic anaemias?
What is the characteristic abnormality seen in the bone marrow erythroblasts in megaloblastic anaemias?
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Which vitamin deficiency is most commonly associated with defective DNA synthesis causing megaloblastic anaemias?
Which vitamin deficiency is most commonly associated with defective DNA synthesis causing megaloblastic anaemias?
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What may cause an elevated MCV as an artefact reported by an automated cell counter in macrocytic anaemia?
What may cause an elevated MCV as an artefact reported by an automated cell counter in macrocytic anaemia?
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What is the underlying defect responsible for the asynchronous maturation of the nucleus in megaloblastic anaemias?
What is the underlying defect responsible for the asynchronous maturation of the nucleus in megaloblastic anaemias?
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Apart from vitamin deficiencies, what else may cause an identical haematological appearance to megaloblastic anaemias?
Apart from vitamin deficiencies, what else may cause an identical haematological appearance to megaloblastic anaemias?
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What is the main plasma-binding protein responsible for delivering Vitamin B12 to the bone marrow and other tissues?
What is the main plasma-binding protein responsible for delivering Vitamin B12 to the bone marrow and other tissues?
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Where does Vitamin B12 become attached to the plasma-binding protein transcobalamin (TC)?
Where does Vitamin B12 become attached to the plasma-binding protein transcobalamin (TC)?
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What is the characteristic abnormality seen in the bone marrow erythroblasts in megaloblastic anemias?
What is the characteristic abnormality seen in the bone marrow erythroblasts in megaloblastic anemias?
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Study Notes
Vitamin B12 and Absorption
- In cyanocobalamin, the reactive center of the vitamin B12 molecule is attached to a cyanide group.
- Vitamin B12 is mainly combined with intrinsic factor (IF) in the stomach for absorption.
- The cubilin receptor directs the endocytosis of the cubilin-IF-B12 complex into the ileal cell for absorption.
Vitamin B12 Release and Absorption
- Gastric acid and pepsin release dietary B12 from food for binding to intrinsic factor (IF) in the stomach.
- The maximum amount of B12 that can be absorbed from a single oral dose via the IF-cubam mechanism is 1.5-2.0 μg.
Megaloblastic Anemias
- The characteristic abnormality seen in the bone marrow erythroblasts in megaloblastic anemias is asynchronous maturation of the nucleus.
- Vitamin B12 deficiency is most commonly associated with defective DNA synthesis, causing megaloblastic anemias.
- Apart from vitamin deficiencies, other conditions like inherited disorders of DNA synthesis may cause an identical hematological appearance to megaloblastic anemias.
Vitamin B12 Transport
- The main plasma-binding protein responsible for delivering Vitamin B12 to the bone marrow and other tissues is transcobalamin (TC).
- Vitamin B12 becomes attached to the plasma-binding protein transcobalamin (TC) in the ileal cells.
Macrocytic Anemia
- In macrocytic anemia, an elevated MCV may be reported as an artefact by an automated cell counter due to the presence of cytoplasmic fragments or Howell-Jolly bodies.
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Description
Learn about the causes of macrocytic anaemia and the different types, including megaloblastic and non-megaloblastic anaemias. Understand the factors that can result in an elevated mean corpuscular volume (MCV) and how it may be an artefact reported by an automated cell counter.
