NUCLEIC ACID

Nucleic acid

Nucleic acid

Nucleic acids

Nucleic acids are macromolecules , polymers formed by repetition of monomers called nucleotides linked by phosphodiester bonds . Form, so long chains or polynucleotides, which makes some of these molecules will finally reach giant sizes (in millions of nucleotides long).

The discovery of nucleic acids is caused by Friedrich Miescher , who in 1869 isolated from cell nuclei an acidic substance which he called nuclein, a name later changed to nucleic acid. Later, in 1953, James Watson and Francis Crick were responsible for the design of DNA .

Types of nucleic acids

There are two types of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), which differ:

On the carbohydrate ( pentose ) containing: the deoxyribose in DNA and ribose in RNA;

For the nitrogenous bases they contain: adenine , guanine , cytosine and thymine in DNA, adenine, guanine, cytosine and uracil in RNA;

In organisms eukaryotes, the structure of DNA is double stranded, while RNA is single stranded structure, but can occur in extended form, such as mRNA , or folded shape, such as tRNA and rRNA .

The molecular mass : the DNA is usually greater than that of RNA.

Nucleosides and Nucleotides

The units that form the nucleic acids are nucleotides . Each nucleotide is a molecule consisting of the union of three units: a monosaccharide five carbons (a pentose , ribose in RNA and deoxyribose in DNA ), a nitrogenous base purine ( adenine , guanine ) or pyrimidine ( cytosine , thymine or uracil ) and one or more phosphate groups ( phosphoric acid ). Both the nitrogenous base and phosphate groups are attached to the pentose (Wolfram ,1984).

The union formed by the pentose and nitrogenous base called nucleoside . When carrying a phosphate unit joined the 5 'carbon of ribose or deoxyribose and the phosphate serves as a liaison between nucleotides, joining the 3' carbon of the next nucleotide, called nucleotide-monophosphate (eg AMP ) where a single phosphate group , nucleotide diphosphate (like ADP ) if it takes two and nucleotide triphosphate (as ATP ) if takes three.

The chemical structure

Nucleic acids are chains of nucleotides as members. The central part of a nucleotide sugar is the ring-shaped molecule (gray in the picture: the ribose). They numbered the carbon atoms of the sugar clockwise from 1-5, so at the C1, a nucleic base (Fig. 1: red, green, yellow and blue) through a glycosidic bond built on. At the C3 has ...