Nucleic acids are large biomolecules that encode genetic information and help to produce functional and structural proteins from that information. They include the familiar DNA and the less familiar but related molecule, RNA. Nucleic acids are polymers, like many other large molecules, and consist of a series of monomers chemically bonded together.
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Monomers and Polymers
Monomer means "one unit," while polymer means "many units." In chemistry, many compounds are polymers, large molecules that consist of repeating identical or very similar units. One way to envision the difference between a monomer and a polymer is to imagine making a chain of paperclips. Each paperclip would be a monomer and the chain would be a polymer. Examples of polymers besides nucleic acids include starch and protein. Plastics, though not components of diet, also are polymers.
The monomers that make up nucleic acids are called nucleotides. Each nucleotide has three parts: a nitrogen-containing base, a sugar and a phosphate group, which is a phosphorus-containing particle. Each nucleotide has the same basic composition; the sugar is ring-shaped, with the nitrogen-containing base attached to one side of the ring and the phosphate group attached farther around the ring, nearly across from the nitrogen-containing base. There are five different nitrogen-containing bases.
The nucleic acids are DNA, which stands for deoxyribonucleic acid, and RNA, or ribonucleic acid. DNA encodes genetic information and is stored in a cell's nucleus, explains Dr. Lauralee Sherwood in her book "Human Physiology." RNA has both structural and functional roles. There actually are several kinds of RNA, but they work together to produce proteins from the information contained in a cell's DNA. They shuttle information out of the nucleus and work to assemble building blocks into protein.
Nucleic Acid Structure
While DNA and RNA are both made of nucleotides, the nucleotides are somewhat different. In the case of DNA, the central sugar is called deoxyribose, while in RNA the central sugar is ribose, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry." Another difference is the overall shape of the polymer; the DNA polymer is ladder-shaped, with two "backbones" of sugar and phosphate and "rungs" made of nitrogen-containing bases. RNA, on the other hand, has a single phosphate and sugar backbone.