Cobalamin: Absorption and Metabolism

The video tutorial explores Vitamin B12, also known as cobalamin, highlighting its unique structure with cobalt at its center. It discusses the limited but crucial roles of B12 in human metabolism, specifically in methionine synthase and methylmalonyl CoA mutase reactions. The video addresses the common deficiency of B12, especially among vegetarians and those consuming processed foods, and explains the complex absorption and metabolism process of B12 in the human body. The importance of B12 in DNA methylation and gene expression is also emphasized.

What is the correct name for Vitamin B12?

• Hydroxocobalamin

• Cyanocobalamin

• Cobalamin

• Methylcobalamin

Which two reactions in humans notably require Vitamin B12?

• Methionine synthase and methylmalonyl CoA mutase

• DNA polymerase and RNA synthase

• Lactate dehydrogenase and pyruvate kinase

• Hexokinase and phosphofructokinase

Why is Vitamin B12 deficiency more common in vegetarians and vegans?

• B12 is synthesized by plants

• B12 is primarily found in animal products

• B12 is destroyed by cooking

• B12 is only found in processed foods

What is the primary source of Vitamin B12 for humans?

• Algae

• Animal products

• Plant-based foods

• Fungi

What element is at the center of the macrocyclic structure of Vitamin B12?

• Cobalt

• Magnesium

• Iron

• Zinc

What role does the R group play in the structure of Vitamin B12?

• It determines the vitamin's properties and reactions

• It binds to intrinsic factor

• It is responsible for DNA methylation

• It stabilizes the vitamin in the stomach

What is the function of intrinsic factor in B12 absorption?

• It transports B12 to the liver

• It neutralizes stomach acid

• It releases B12 from dietary protein

• It binds to B12 for absorption in the ileum

How is Vitamin B12 absorbed in the small intestine?

• Through receptor-mediated endocytosis

• By passive diffusion

• Via active transport

• Through osmosis

What is the role of methionine synthase in the body?

• It transports B12 in the blood

• It breaks down fatty acids

• It uses B12 to convert homocysteine to methionine

• It synthesizes DNA

Why is Vitamin B12 essential for DNA methylation?

• It stabilizes the DNA structure

• It binds to DNA methyltransferase

• It directly methylates DNA

• It is required for the production of SAM