how does the body metabolize benzene?

Question

for chemistery

Answer 1

Cytochrome P4502E1, and perhaps other cytochromes P450, can generate H2O2 when acting as oxidases of nicotinamide adenine dinucleotide phosphate (NADPH). The hydroxyl radical formed from H2O2 can hydroxylate benzene to yield phenol. An alternative mechanism for phenol formation is seen in Figure 2, which is designed to reflect on the fate of the benzene oxide-oxepin system. When benzene oxide is the first product, it can rearrange nonenzymatically to form phenol. Alternatively, benzene oxide can be hydrated via epoxide hydrolase to yield 1,2-benzene dihydrodiol, which can in turn be oxidized via dihydrodiol dehydrogenase to form catechol. The reaction of benzene oxide with glutathione catalyzed by glutathione S-transferase leads to the formation of the premercapturic acid. It is likely that benzene oxide or its oxepin are precursors to ring opening (12). Phenol can be further hydroxylated to form hydroquinone or catechol. In theory, 1,2,4-benzenetriol may be formed by the hydroxylation of either hydroquinone or catechol; but Inoue et al. (13) suggested that catechol is not a precursor of 1,2,4-benzenetriol in humans.

For a graphical presentation, see the source link.

Answer 2

Ok, the body uses an enzyme in the liver to form an epoxide between two carbons of the benzene ring. Then, this epoxide is attacked by an amino acid while DNA replicates. Because the amino acid is corrupted, the DNA can no longer replicate properly. This leads to a point-mutation.

If you are unlucky, the point mutation will occur at an oncogene, turning the cell cancerous. Usually a number of mechanisms will kill these cells. However, there is a possibility that the body will not. In these cases, a cancer develops.

Answer 3

There are specific enzymes (namely cytochrome P450) which metabolize aromatic compounds by epoxidation of the double bonds. These epoxides are further metabolized by epoxide hydrolases, which yield more polar diols. These diols undergo further metabolism to lead to quinone compounds, which can be easily degraded.

Answer 4

My understanding is that it doesn't. It bioaccumulates in fat cells. Benzene is very stable and not overly reactive it is not soluble in water and is thus very difficult for the body to remove.

Compare this with toluene. The body can apparently grab hold of the CH3 group and oxidise it to benzoic acid. This is water soluble and can be removed by the kidneys.

Answer 5

It cannot, benzene is a carcinogen, it causes cancer.