|MadSci Network: Molecular Biology|
As heterotrophs (organisms which get their building materials from the consumption of others), humans get much of their nucleotides from their diet, by breaking down the DNA and RNA in the cells of the organisms we digest. However, this is not always suf ficient to supply or cells with enough nucleotides to function, so all cells in the human body have the ability to synthesize nucleotides from other raw materials. In fact, the de novo synthesis of nucleotides in most humans is sufficient to make dietary intake of nucleotides unnecessary. The syntheses of the purine and pyrimidine nucleotides are carried out by several enzymes in the cytoplasm of the cell, not within a specific organelle.
There are some people who are born with a genetic deficiency in one of the enzymes necessary for the metabolism of nucleotides. Lesch-Nyhan Syndrome is an X-linked genetic disor der affecting guanine metabolism, which results in retardation and other nervous system disorders. SCID (for severe combined immunodeficiency) is a genetic disorder affecting adenine metabolism, which results in the loss of all lymphocytes from the body. If you look through the pathways in some of the above links, you will see that many of the precursors of nucleotides are the products of glycolysis and amino acid metabolism, which also occur in the cytoplasm.
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