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Vitamin B12

life science Maturity 11-13 Next article →

Vitamin B12 is a vital nutrient known as cobalamin or extrinsic factor. It belongs to a group of eight B vitamins. This vitamin is essential for metabolism, which is how our bodies process energy. It acts as a cofactor, meaning it is required for certain enzyme-catalyzed reactions to occur.

Cobalamin-general-structure-color
Cobalamin-general-structure-color

Without this cofactor, many biological processes would stop. B12 is the most chemically complex of all known vitamins.

At its core, B12 is a coordination complex. It features a cobalt atom at its center. This cobalt atom sits inside a structure called a corrin ligand. The complex is also bound to a benzimidazole ligand and an adenosyl group.

B12 methylcobalamin
B12 methylcobalamin

Because of this structure, B12 can perform many different tasks. It serves as a vital helper in DNA synthesis. It also aids in the metabolism of fatty acids and amino acids. These processes keep our cells functioning and growing correctly.

There are several different forms of this vitamin, called vitamers. Each form has a specific structure based on what is attached to the cobalt. For example, methylcobalamin has a methyl group attached. This form works in the cytosol, which is the fluid inside cells. Adenosylcobalamin has an adenosyl group and works in the mitochondria.

Folate methionine cycle
Folate methionine cycle

Cyanocobalamin is a manufactured form where a cyanide group is attached. This form is very stable and is often used in food fortification and supplements. Because it is stable, it does not break down easily.

B12 is produced exclusively by certain bacteria and archaea. Animals must consume B12 through their diet to survive. Plants do not require B12 because they use different enzymatic pathways. Natural sources for humans include meat, poultry, fish, shellfish, eggs, and dairy.

Methylcobalamin tablets
Methylcobalamin tablets

Many breakfast cereals also include B12 through food fortification. People can also take B12 as dietary supplements or pharmaceutical medicines. These are often taken orally, but doctors may use intramuscular injections for treatment.

Deficiency in B12 can lead to serious health issues. One major problem is megaloblastic anemia. This happens when the body cannot perform proper DNA synthesis. This inhibition affects the production of purines and thymidine.

Propionate pathway
Propionate pathway

Another serious issue is damage to the nervous system. B12 supports the synthesis of myelin, which is the protective coating on nerves. A lack of B12 can cause neuropathy or even irreversible nerve damage. Symptoms can include fatigue, memory problems, and even psychosis.

Certain groups are at a higher risk for deficiency. Vegans are at risk because plant foods do not provide enough B12. In Hong Kong and India, roughly 80% of vegans have been found to be deficient. Vegetarians are also at risk, with studies showing 40% to 80% deficiency in those who do not use supplements. The elderly are also vulnerable. This is often due to achlorhydria, which is a reduction in stomach acid. Less acid makes it harder for the body to absorb the vitamin.

B12 is especially critical during pregnancy and childhood. Low maternal levels increase the risk of miscarriage and preterm birth. The placenta works to concentrate B12 for the developing fetus.

Hydroxocobalamin Injection
Hydroxocobalamin Injection

If a mother is deficient, her breast milk may also have low levels. This can lead to developmental delays or anemia in infants. In children, untreated deficiency can cause involuntary movements and poor physical growth. Maintaining proper levels is vital for long-term neurological health.

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🖼️ Images & Media (7)
File:Hydroxocobalamin Injection.jpg
Hydroxocobalamin Injection.jpg
File:Methylcobalamin tablets.jpg
Methylcobalamin tablets.jpg
File:B12 methylcobalamin.jpg
B12 methylcobalamin.jpg
File:Cobalamin-general-structure-color.png
Cobalamin-general-structure-color.png
File:Propionate pathway.svg
Propionate pathway.svg
File:Folate methionine cycle.svg
Folate methionine cycle.svg
File:Complex human TCII-Vitamin B12.jpg
Complex human TCII-Vitamin B12.jpg
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