Medicine Quiz-5:
Megaloblastic Anemia

Megaloblastic Anemia

Which of the following is major natural cobalamin?

Correct! Wrong!

Forms of cobalamin -


• Adenosylcobalamin • Cyanocobalamin • Hydroxocobalamin • Methylcobalamin

Which of the following helps in protection of the acid-sensitive vitamin B12 while it moves through the stomach?

Correct! Wrong!

Essential function of haptocorrin is protection of the acid-sensitive vitamin B12 while it moves through the stomach

Cobalamin requires Intrinsic Factor for absorption in ------------ cases

Correct! Wrong!

Cobalamin requires IF for absorption - 99%. Free cobalamin is absorbed passively in the terminal ileum -1%. This why oral replacement with large vitamin is required in pernicious anemia

Cobalamin is synthesized by -

Correct! Wrong!

Cobalamin is synthesized solely by microorganisms.

Methylmalonyl coenzyme A mutase uses -------------- to convert L-methylmalonyl-CoA to succinyl-CoA, an important step in the catabolic breakdown of some amino acids into succinyl-CoA.

Correct! Wrong!

Methylmalonyl coenzyme A mutase (MUT) is an isomerase enzyme which uses the Adenosylcobalamin form to convert L-methylmalonyl-CoA to succinyl-CoA, an important step in the catabolic breakdown of some amino acids into succinyl-CoA, which then enters energy production via the citric acid cycle.


Methylmalonyl-CoA mutase (MCM) [mitochondrial] also known as methylmalonyl-CoA isomerase
Methylmalonyl-CoA mutase is a vitamin B12-dependent enzyme that catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA in humans. This functionality is lost in vitamin B12 deficiency, and can be measured clinically as an increased serum methylmalonic acid (MMA) concentration.

Intrinsic Factor for Vitamin -B12 is produced by which cells?

Correct! Wrong!

IF is produced in the gastric parietal cells of the fundus and body of the stomach, and its secretion parallels that of hydrochloric acid.


Gastric cells -
Cells found in the gastric glands include -
-Foveolar cells - also called mucous neck cells - produce mucus
-Chief cells - Zymogen cells/ peptic cells - zymogens – pepsinogen (precursor to pepsin) and prorennin [in childhood only ]
-Parietal cells - oxyntic cells -secrets : HCl , castle's intrinsic factor
-G cells - secret : gastrin hormone
-D-cells - secret : somatostatin
-Enterochromaffin- like cells (ECLs) - release serotonin and histamine

Bioactive forms of vitamin B12 in mitochondria?

Correct! Wrong!

Bioactive forms of vitamin B12 -


• Methylcobalamin in cytosol
• Adenosylcobalamin in mitochondria

Which of the following has a cobalt atom at the center of a corrin ring?

Correct! Wrong!

Vitamin B12 - has a cobalt atom at the center of a corrin ring.

Cubilin receptors are present in -

Correct! Wrong!

Cubilin receptors are present in -


- Ileum - helps to absorb Vitamin B12 - IF Complex
- Yolk sac
- Renal proximal tubular epithelium

Transcobalamin-1 [Haptocorrin] is derived primarily from -

Correct! Wrong!

Transcobalamin-1 [Haptocorrin] is derived primarily from the specific granules in neutrophils.

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