Chemistry - Vitamin B12 - Research Paper Example

The cobalt ? position, which is the region below the corrin ring plane, may either be open or could be occupied by a side chain of a heterocyclic nitrogen or the solvent (Combs 55). Methyl, nitro, aqua, sulfato, sulfito, hydroxo, 5-deoxyadenosyl, Br-, CN- or a Cl- group may occupy the cobalt ? position, which is the region above the corrin ring plane (Combs 55). The molecule is an octahedral complex, which apart from the corrin ring, also contains a nucleotide along with another cobalt bound group.

The corrin ring is formed of four pyrrole rings, three of which are linked with methylene bridges and one with a direct bond. The cobalt atom (Co3+) at the center of the corrin ring is triply ionized and is bound to the nitrogen atoms of the four pyrrole rings (Combs 56). Chemistry Removal of the central cobalt atom of the molecule results in loss of biological activity. Like all corrinoids, vitamin B12 is a crystalline substance with absorption spectra above 300 nm due to ?-? transitions in the corrin ring (Combs 56).

It is yellow, red or red-orange in color, is soluble in water, fairly heat stable, and decomposes above 210°C (Combs 57). . Functions and Mechanism Vitamin B12 has a key role in the metabolism of folate in the human body (Insel et al. 452). It transfers a methyl group from the folate coenzyme Tetrahydrofolic acid (THFA) converting THFA to its methylene form. In absence of the vitamin, THFA cannot transform into its methylene form, which is its active form that is involved in many metabolic pathways (Insel et al. 452). As THFA is involved in folate metabolism, deficiency of vitamin B12 results in the deficiency of folate because of absence of active form of THFA.

Therefore, vitamin B12 deficiency amounts to folate deficiency, which in turn leads to megaloblastic anemia. Several enzymes that convert homocysteine to methionine are also dependant on vitamin B12 and THFA. Conversion of homocysteine to methionine reduces the levels of homocysteine in the blood, thereby lowering the risk of heart diseases. This mechanism is affected in case of vitamin B12 deficiency (Insel et al. 453). Vitamin B12 also functions in the maintenance of the myelin sheath, which is a protective coat surrounding nerve fibres (Insel et al. 453). Moreover, some fatty acid chains require rearrangement of their carbon atoms in order to enter the citric acid cycle.

This function is also performed by vitamin B12 (Insel et al. 453). Vitamin B12 is stored in the liver and can last for about 2 years, while the symptoms of its deficiency may not be apparent for up to almost 12 years (Insel et al. 454). Anemia is the major outcome of vitamin B12 deficiency. In absence of vitamin B12 and in turn, folate, megaloblasts are formed instead of red blood cells, leading to megaloblastic anemia. Vitamin B12 deficiency also results in cognitive defects by causing