The basis of cell activity of living organisms are a function of biological polymers, nucleic acids, carbohydrates, proteins and lipids.Biopolymers consist of monomers, hydrocarbon structures which include nitrogen, oxygen, sulfur and phosphorus.
In the 19th century began to study the structure of substances that make up living cells, but the function of DNA, proteins, RNA, and their structures were determined definitively in the 20th century.
Friedrich Miescher in 1868 isolated from cell nuclei of leukocytes phosphorous and called it nukleina.Then Richard Altman in 1889 determined that this substance consists of special acids and protein.Then for the first time and heard about the term "nucleic acid".However, to establish the function of nucleic acids was still far off.
DNA - deoxyribonucleic acid - is the largest biological polymers consisting of hundreds of monomers - deoxyribonucleotides.In their composition, except for sugar (deoxyribose), includes 4 types of nucleotides: adenine - A, thymidine - T, cytosine - C, guanine - G.
first time DNA was considered a nucleic acid of animal origin, as it was isolated from the thymus of animalsand RNA was isolated from wheat germ - vegetable.It was believed that at last found a biochemical difference between plant and animal cells.However, in the mid-twentieth century they found that RNA and DNA are included in all cells.
structure of nucleic acids immediately began studying Erwin Chargaff, who in 1953 found that the nucleotides that make up the homonymous acids are paired with strict regularity.
in connection enter always the pyrimidine and purine bases one, T = C, A = T. That is, adenine binds to thymidine, and guanine - with cytosine.
and the function of DNA is essential that the connection in the first case, provide two pairs of hydrogen, while the second - three.
Chargaff's rules proved the foundation on which Watson and Crick built a double-helix structure of DNA.
In this molecule, like a protein molecule distinguishes primary, secondary and tertiary structures.
primary structure - a linear sequence of monomers in a chain.
Of course, in the nature of the DNA in a single chain does not occur, but here we are talking about the primary structure of the biopolymer, which defines all of its properties.
Secondary structure - a spatial characteristic of the biopolymer.In the case of DNA, it is a two polynucleotide chains, each of which is twisted into a spiral to the right, and both are simultaneously twisted in a clockwise direction around the common axis.These chains are held close by the hydrogen bonds.The tertiary structure of the DNA helix is ​​determined by further molecules.
giant step forward was taken with the discovery that the function of DNA is to transfer and storage of genetic information.DNA contains the genetic program of the structure of proteins specific to each organism.These RNA molecules with the genetic information is transmitted from organism to organism.The function of DNA also includes implementation of genetic information.They are involved in the processes of transcription, translation and replication, thus ensuring the synthesis of various proteins.
