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RNA and DNA. RNA is what? RNA: structure, functions, types

The time in which we live is marked by tremendous changes, tremendous progress, when people get answers to more and more new questions. Life is rapidly moving forward, and what only recently seemed impossible, begins to be realized. It is possible that today is a story from the fantasy genre, soon it will also acquire the features of reality.

One of the most important discoveries in the second half of the twentieth century were the nucleic acids RNA and DNA, thanks to which the person approached the clues to the secrets of nature.

Nucleic acids

Nucleic acids are organic compounds that have high molecular weight properties. They include hydrogen, carbon, nitrogen and phosphorus.

They were discovered in 1869 by F. Micher, who examined pus. However, then his discovery was not given much importance. Only later, when these acids were found in all animal and plant cells, came the understanding of their enormous role.

There are two kinds of nucleic acids: RNA and DNA (ribonucleic and deoxyribonucleic acids). This article is devoted to ribonucleic acid, but for a general understanding, we will also consider what DNA is itself.

What is deoxyribonucleic acid?

DNA is a nucleic acid consisting of two strands that are connected according to the complementarity law by hydrogen bonds of nitrogenous bases. Long chains are twisted into a spiral, one turn contains almost ten nucleotides. The diameter of the double helix is two millimeters, the distance between nucleotides is about half a nanometer. The length of one molecule sometimes reaches several centimeters. The DNA length of the nucleus of the human cell is almost two meters.

The DNA structure contains all the genetic information. DNA has replication, which means a process in which two exactly identical children are formed from one molecule.

As already noted, the chain consists of nucleotides consisting, in turn, of nitrogenous bases (adenine, guanine, thymine and cytosine) and the residue of phosphorus acid. All nucleotides differ in nitrogen bases. The hydrogen bond does not arise between all bases, adenine, for example, can only be combined with thymine or guanine. Thus, the adenyl nucleotides in the body are as much as the thymidyl nucleotides, and the number of guanyls is equal to cytidyl (Chargaff's rule). It turns out that the sequence of one chain predetermines the sequence of the other, and the chains seem to mirror each other. This pattern, where the nucleotides of two chains are arranged in an orderly manner, and also are selectively connected, is called the principle of complementarity. In addition to hydrogen compounds, the double helix interacts and hydrophobic.

The two chains are multidirectional, that is, they are located in opposite directions. Therefore, opposite the three-end of one is the five-end of the other chain.

Externally , the DNA molecule resembles a screw staircase, the rail of which is a sugar-phosphate backbone, and the steps are complementary nitrogen bases.

What is ribonucleic acid?

RNA is a nucleic acid with monomers called ribonucleotides.

By chemical properties, it is very similar to DNA, since both are nucleotide polymers that are a phosphorylated N-glycoside that is built on the residue of pentose (five-carbon sugar), with the phosphate group of the fifth carbon atom and the nitrogen base at the first carbon atom.

It is a single polynucleotide chain (other than viruses), which is much shorter than DNA.

One RNA monomer is the remains of the following substances:

  • Nitrogen bases;
  • A five-carbon monosaccharide;
  • Acid phosphorus.

RNAs have pyrimidine (uracil and cytosine) and purine (adenine, guanine) bases. Ribose is a monosaccharide of the nucleotide RNA.

Differences between RNA and DNA

Nucleic acids differ from each other in the following properties:

  • The amount of it in the cell depends on the physiological state, age and organ;
  • DNA contains carbohydrate deoxyribose, and RNA - ribose;
  • The nitrogenous base in DNA is thymine, and in RNA - uracil;
  • Classes perform different functions, but are synthesized on a DNA matrix;
  • DNA consists of a double helix, and RNA - from a single chain;
  • For her, the rules of Chargaff acting on DNA are uncharacteristic;
  • In RNA more minor bases;
  • The chains differ substantially in length.

Study history

The RNA cell was first discovered by the biochemist from Germany R. Altman in the study of yeast cells. In the middle of the twentieth century, the role of DNA in genetics was proved. Only then did they describe the types of RNA, functions, and so on. Up to 80-90% of the mass in the cell is accounted for by r-RNA, forming together with the ribosome proteins and participating in protein biosynthesis.

In the sixties of the last century, it was first suggested that there should be a kind that carries genetic information for protein synthesis. After that, it was scientifically established that there are informational ribonucleic acids representing complementary copies of genes. They are also called matrix RNAs.

The decoding of the information recorded in them involves so-called transport acids.

Later, methods were developed to detect the sequence of nucleotides and establish the structure of RNA in the space of the acid. So it was discovered that some of them, which are called ribozymes, can split the polyribonucleotide chains. As a consequence, it was assumed that at the time when life on the planet was born, RNA acted without DNA and proteins. At the same time, all transformations were made with her participation.

The structure of the ribonucleic acid molecule

Almost all RNA are single chains of polynucleotides, which, in turn, consist of monoribonucleotides - purine and pyrimidine bases.

Nucleotides are designated by the initial letters of the bases:

  • Adenine (A), A;
  • Guanine (G), G;
  • Cytosine (C), C;
  • Uracil (U), U.

They are linked together by three- and five-phosphodiester bonds.

The most diverse number of nucleotides (from several tens to tens of thousands) is included in the structure of RNA. They can form a secondary structure, consisting mainly of short double-stranded strands, which are formed by complementary bases.

Structure of a molecule of ribonucleic acid

As already mentioned, the molecule has a single-stranded structure. RNA gets a secondary structure and shape as a result of the interaction of nucleotides with each other. It is a polymer whose monomer is a nucleotide consisting of sugar, a phosphorus acid residue and a nitrogen base. Externally, the molecule is similar to one of the strands of DNA. Nucleotides adenine and guanine, which are part of RNA, are purine. Cytosine and uracil are pyrimidine bases.

Synthesis process

For the RNA molecule to be synthesized, the matrix is a DNA molecule. It happens, however, and the reverse process, when new molecules of deoxyribonucleic acid are formed on the ribonucleic matrix. This occurs when certain types of viruses are replicated.

The basis for biosynthesis can also serve other molecules of ribonucleic acid. In its transcription, which occurs in the nucleus of the cell, many enzymes participate, but the most significant of them is RNA polymerase.

Kinds

Depending on the type of RNA, its functions also differ. There are several types:

  • Information and RNA;
  • Ribosomal p-RNA;
  • Transport tRNA;
  • Minor;
  • Ribozymes;
  • Virus.

Information ribonucleic acid

Such molecules are also called matrix molecules. They make up about two percent of the total in the cell. In eukaryotic cells, they are synthesized in nuclei on DNA matrices, then passing to the cytoplasm and binding to the ribosomes. Further, they become matrices for protein synthesis: they are joined by transport RNAs that carry amino acids. This is the process of transforming information, which is realized in a unique protein structure. In some viral RNAs, it is also a chromosome.

Jacob and Mano are the discoverers of this species. Not having a rigid structure, its chain forms curved loops. Without working, i-RNA gathers into folds and folds into a tangle, and in working order unfolds.

And-RNA carries information about the sequence of amino acids in the protein that is synthesized. Each amino acid is encoded in a specific place with the help of genetic codes that are characteristic of:

  • Triplet - from four mononucleotides it is possible to build sixty-four codons (genetic code);
  • Non-overlapping - information moves in one direction;
  • Continuity - the principle of operation is reduced to the fact that one i-RNA is a single protein;
  • Universality - this or that kind of amino acid is coded in all living organisms equally;
  • Degeneracy - twenty amino acids are known, and codons are sixty-one, that is, they are encoded by several genetic codes.

Ribosomal ribonucleic acid

Such molecules constitute the vast majority of cellular RNAs, namely from eighty to ninety percent of the total. They combine with proteins and form ribosomes - these are organoids that perform protein synthesis.

Ribosomes consist of sixty-five percent of r-RNA and thirty-five percent of protein. This polynucleotide chain is easily bent along with the protein.

The ribosome consists of the amino acid and peptide sites. They are located on contacting surfaces.

Ribosomes move freely in the cell, synthesizing proteins in the right places. They are not very specific and can not only read information from i-RNA, but also form a matrix with them.

Transport ribonucleic acid

T-RNA are the most studied. They make up ten percent of cellular ribonucleic acid. These types of RNA bind to amino acids thanks to a special enzyme and are delivered to the ribosomes. In this case, amino acids are transported by transport molecules. However, it happens that the amino acid is encoded by different codons. Then they will be transported by several transport RNAs.

It folds into a glomerulus, when it is inactive, but functions as a clover leaf.

It distinguishes the following areas:

  • The acceptor stem, which has the nucleotide sequence of ATSTS;
  • A site serving to join the ribosome;
  • An anticodon encoding an amino acid that is attached to this tRNA.

Minor type of ribonucleic acid

Recently, RNA species have replenished with a new class, the so-called small RNAs. They are most likely universal regulators that turn genes on or off in embryonic development, and also control processes inside cells.

Ribozymes are also newly discovered, they actively participate when the RNA acid is fermented, being a catalyst.

Viral types of acids

The virus can contain either ribonucleic acid or deoxyribonucleic acid. Therefore, with the corresponding molecules, they are called RNA-containing. When a virus enters this cell, reverse transcription occurs - new DNA is created on the basis of ribonucleic acid, which are embedded in the cells, ensuring the existence and reproduction of the virus. In the other case, the formation of complementary RNA occurs. Protein viruses, vital activity and reproduction go without DNA, but only on the basis of information contained in the RNA of the virus.

Replication

In order to improve the general understanding, it is necessary to consider the replication process, which results in the appearance of two identical nucleic acid molecules. This is how cell division begins.

It involves DNA polymerases, DNA-dependent, RNA polymerases and DNA ligases.

The replication process consists of the following steps:

  • Despiralization - there is a gradual unwinding of the maternal DNA, which captures the entire molecule;
  • The breaking of the hydrogen bonds, in which the chains diverge, and a replicative fork appears;
  • Adjustment of dNTP to the liberated bases of the mother circuits;
  • The removal of pyrophosphates from dNTP molecules and the formation of phosphoric-dinether bonds due to the evolving energy;
  • Respiration.

After the formation of a daughter molecule, the nucleus, the cytoplasm and the rest are divided. Thus, two daughter cells are formed, fully received all the genetic information.

In addition, the primary structure of proteins is encoded, which are synthesized in the cell. DNA in this process takes an indirect part, and not a direct one, that it is the DNA that is involved in the synthesis of proteins and RNA. This process is called transcription.

Transcription

Synthesis of all molecules occurs during transcription, that is, rewriting genetic information from a specific DNA operon. The process at some points is similar to replication, but in others it differs significantly from it.

The similarities are the following parts:

  • Beginning comes with DNA despiralization;
  • There is a break in the hydrogen bonds between the bases of the chains;
  • Complementary to them are NTFs;
  • The formation of hydrogen bonds takes place.

Differences from replication:

  • During transcription, only the DNA portion corresponding to the transcripton is unraveled, while during the replication the entire molecule undergoes a cleavage;
  • When transcribed, tunable NTFs contain ribose, and instead of thymine, uracil;
  • Information is written off only from a certain site;
  • After the molecule is formed, the hydrogen bonds and the synthesized chain break, and the chain slides off the DNA.

For normal functioning, the primary structure of RNA should consist only of decommissioned DNA from exon sites.

The newly formed RNA begins the maturation process. Silent sections are cut out, and informative ones are sewn together, forming a polynucleotide chain. Further, each species has its own transformations.

In i-RNA, attachment to the initial end occurs. The polyadenylate is added to the final site.

In the tRNA, bases are modified to form minor species.

In r-RNA, separate bases are also methylated.

Protect from destruction and improve transport to the cytoplasm of proteins. RNA in a mature state is connected with them.

The value of deoxyribonucleic and ribonucleic acids

Nucleic acids are of great importance in the life of organisms. In them is stored, transferred to the cytoplasm and transmitted by inheritance to daughter cells information about proteins synthesized in each cell. They are present in all living organisms, the stability of these acids plays a crucial role for the normal functioning of both cells and the whole organism. Any changes in their structure will lead to cellular changes.

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