Nucleotides are a class of chemicals in the body with several important functions. These chemicals help form the blueprints of the cell -- DNA. DNA is transcribed, or copied, into a similar code on RNA, which is also made of nucleotides. DNA and RNA are both types of nucleic acids. In addition, nucleotides help carry and deliver energy, as well as help some enzymes to function.
Types of Nuceotides
There are a number of functional nucleotides, plus some that are metabolic by-products. Gaunine and adenosine are a class of nucleotides known as purines. Another class of nucleotides includes the pyrimidines: thymine, cytosine and uracil. Purines and pyrimidines are found in DNA and RNA.
Nucleic Acids
DNA is composed of the nucleotides adenine, cytosine, gaunine and thymine. DNA resembles a ladder that is twisted into a spiral; this structure is called a double helix. In DNA, adenine binds to thymine and gaunine binds to cytosine. These nucleotides are arranged in sequence, forming a code. Every three nucleotides is called a codon, and a sequence of codons tells the cell which amino acids to use in building a protein. In order for this to occur, DNA is transcribed onto RNA, and the RNA is translated into proteins for use by the cells.
Functions
As described, purines and pyrimidines help construct DNA and RNA. In addition, the purines adenine and guanine carry energy when bound to phosphate, as the chemicals ATP and GTP. Other modifications make these nucleotides into the chemicals cAMP and cGMP, which help modify cell functions.
Disorders
There are many disorders involving nucleotides. In gout, a metabolic waste product of purines called uric acid builds up in the body. High levels of the chemical can crystallize in the joint, causing inflammation and pain. Problems with purine and pyrimidine metabolism can lead to nerve damage and developmental delay.
References
- "Lehninger Principles of Biochemistry," 4th Ed.; David L. Nelson, et al.; 2004
- "Molecular Biology of the Cell," 4th Ed.; Bruce Alberts, et al.; 2002
- "Robbins and Cotran Pathologic Basis of Disease," 8th Ed.; Vinay Kumar, et al.; 2009
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