Nucleic acids play an important role in the cell, ensuring its vitality and reproduction.These properties make it possible to call them the second most important after the biological molecules of proteins.Many researchers even render DNA and RNA in the first place, meaning their major importance in the development of life.Nonetheless, they are destined to take the second place after the proteins, because the foundation of life is just polipetidnaya molecule.
nucleic acids - this is a different level of life is much more complex and interesting because of the fact that each type of molecule has a specific job for her.This is necessary to understand in more detail.
concept of nucleic acids
all nucleic acids (DNA and RNA) are a heterogeneous biological polymers, which differ in the number of circuits.Double-stranded DNA is a polymer molecule that contains genetic information of eukaryotic organisms.Circular DNA molecules may contain genetic information of some viruses.This HIV and adenovirus.There is also a special type of DNA 2: mitochondrial and plastid (located in the chloroplasts).
RNA also has a lot more species that due to the different functions of nucleic acids.There are nuclear RNA, which contains the genetic information of bacteria and most viruses, the matrix (or messenger RNA), ribosomal and transport.All of them are involved in storing or genetic information, or gene expression.However, which functions in a cell operate nucleic acid is necessary to understand in greater detail.
double-stranded DNA molecule
This type of DNA - a perfect storage of genetic information.Double-stranded DNA molecule is a single molecule consisting of heterogeneous monomers.Their task is the formation of hydrogen bonds between nucleotides of the other chains.Himself monomer DNA consists of a nitrogenous base, balance and five-carbon monosaccharide orthophosphate deoxyribose.Depending on what type of nitrogenous base underlies a specific DNA monomer, it has the name.Types of DNA monomers:
- deoxyribose with residual orthophosphate and nitrogenous base adenine;
- thymidine nitrogenous base and a deoxyribose moiety orthophosphate;
- nitrogenous base cytosine, and the residue desoksiriboza orthophosphate;
- orthophosphate with deoxyribose and nitrogenous guanine residue.
In a letter to simplify the circuit structure of DNA adenylic remainder is designated as "A", guanine - "G", thymidine - "T", and cytosine - "C".Importantly, the genetic information is transferred to double-stranded DNA molecules on the messenger RNA.Differences her bit: here as the carbohydrate moiety has not deoxyribose and ribose, and instead thymidylic nitrogenous base uracil found in RNA.
Structure and function of DNA
DNA is built on the principle of biological polymer in which one chain is created in advance in a predetermined pattern, depending on the genetic information of the parent cell.Nukleodidy DNA are connected by covalent bonds.Then, on the basis of complementarity to the nucleotides of the single-stranded molecules joined by other nucleotides.If the single-stranded molecule is represented by the beginning of adenine nucleotide, in the second (complementary) circuit it will fit thymine.Guanine is complementary to cytosine.Thus, double-stranded DNA molecule is constructed.It is located in the nucleus and stores the hereditary information that is encoded codons - triplets of nucleotides.Features double-stranded DNA:
- saving resulting from the parent cell hereditary information;
- gene expression;
- obstacle to change the nature of the mutation.
value proteins and nucleic acids
believed that the function of proteins and nucleic acids common, namely, they are involved in gene expression.Nucleic acid itself - is their storage and protein - is the end result of reading information from a gene.Gene itself is an integral portion of one DNA molecule packaged in the chromosome, in which information is recorded by the nucleotides of the structure of a protein.One gene encodes the amino acid sequence of only one protein.It will implement the protein hereditary information.
Classification of RNA
functions of nucleic acids in the cell are very diverse.And they are most numerous in the case of RNA.However, this multifunctionality is still relative, because one type of RNA is responsible for one of the functions.At the same time, there are the following types of RNA:
- nuclear RNA viruses and bacteria;
- matrix (information) RNA;
- ribosomal RNA;
- messenger RNA plasmids (chloroplasts);
- chloroplast ribosomal RNA;
- mitochondrial ribosomal RNA;
- mitochondrial messenger RNA;
- transfer RNA.
functions of RNA
This classification includes several types of RNA, which are divided depending on location.However, in functional terms, they should be divided only 4 types: a nuclear, information, ribosomal and transport.Ribosomal RNA function is protein synthesis based on the nucleotide sequence of the mRNA.Thus amino acids "Tray" to ribosomal RNA "strung" on the messenger RNA, by means of transfer ribonucleic acid.Since synthesis occurs in any organism which has a ribosome.The structure and function of nucleic acids and provide preservation of the genetic material and the creation process of protein synthesis.
mitochondrial nucleic acid
If what functions in the cell perform nucleic acids located in the nucleus or cytoplasm of virtually all known, of the mitochondrial and plastid DNA information is not enough.It also found specific ribosomal and messenger RNA.Nucleic acids DNA and RNA are present here even the most autotrophic organisms.
Perhaps nucleic acid enters the cell by symbiogenesis.This path is considered by scientists as the most likely because of the lack of alternative explanations.The process is seen as follows: inside the cell in a certain period came symbiontic avtorofnaya bacterium.As a result, the nuclear-free cell lives inside the cell and provides it with energy, but gradually degrades.
In the initial stages of evolutionary development, probably nuclear-free symbiotic bacteria moved mutational processes in the nucleus of the host cell.This enabled the genes responsible for maintaining information about the structure of mitochondrial proteins, nucleic acid penetrate into the host cell.However, so far about what function within the cell, nucleic acid operate mitochondrial origin information is not much.
probably in the mitochondria of the synthesized proteins whose structure is not encoded nuclear DNA or RNA host.It is also likely that the mechanism of its own cell protein synthesis is needed because many of the proteins synthesized in the cytoplasm, can not get through the double membrane of the mitochondria.The data organelles produce energy, but because in the event of a specific channel or carrier for the protein it will be enough for the movement of molecules against a concentration gradient.
Plasmid DNA and RNA
plastids (chloroplasts) also has its own DNA, which is probably responsible for implementing similar functions as in the case of mitochondrial nucleic acids.There is also and its ribosomal, matrix, and transfer RNA.Wherein plastids, judging by the number of membranes, and not by the number of biochemical reactions that are more complicated.It happens that many plastids with 4 layers of membranes, which can be explained by scientists in different ways.
One thing is clear: the function of nucleic acids in the cell is not fully understood.It is not known how important mitochondrial protein synthesizing system and similar to her hloroplasticheskaya.It is also not clear why the cells need mitochondrial nucleic acids when proteins (obviously not all) already encoded in the nuclear DNA (or RNA, depending on the organism).Although some of the facts are forced to accept that the protein synthesizing system of mitochondria and chloroplasts is responsible for the same functions as the DNA of the nucleus and cytoplasm RNA.They preserve genetic information, reproduce and transmit it to daughter cells.
Summary
is important to understand what the function is performed in the cell nucleic acid nuclear, plastid and mitochondrial origin.This opens up many prospects for science, in fact symbiotic mechanism, according to which there were many autotrophic organisms that can be played today.This will provide a new type of cells, perhaps even human.Although the prospects for the implementation of mnogomembrannyh plastid organelles in cells too early to say.
much more important to understand that in the cell nucleic acids are responsible for virtually all processes.This protein biosynthesis and storing information about the structure of the cell.And more importantly, that the nucleic acids act as transfer of genetic material from parent cell to daughter cell.This ensures the further development of evolutionary processes.
