Proteins, unlike nucleic acids 1. participate in the formation of the plasma membrane 2. are part of chromosomes 3. are accelerators chemical reactions 4. carry out a transport function 5. perform a protective function 6. transfer hereditary information from the nucleus to the ribosomes
Answers:
135! tRNA also performs a transport function in protein biosynthesis. And at 6 this function is performed by tRNA
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Nucleoproteins are one of the most important groups of proteins, consisting of simple proteins associated with nucleic acids. These proteins play a primary role in the storage and transmission of genetic information and protein biosynthesis and are found mainly in the nuclei of cells. Deoxyribonucleoproteins contain deoxyribonucleic acid (DNA). Ribonucleoproteins contain ribonucleic acid (RNA)
Phosphoproteins - These proteins contain organically bound, labile phosphate, which is absolutely necessary for the cell to perform a number of biological functions. In addition, they are a valuable source of energy and plastic material during the growth and development of embryos and young growing organisms. The most studied phosphoproteins are milk casein, egg yolk vitellin, fish roe ichtulin. Along with protein, metalloproteins contain ions of a metal or several metals. Metalloproteins have different functions. For example, the protein transferrin (contains iron) serves as a physiological carrier of iron in the body. Other metalloproteins are biological catalysts-enzymes - amylases (contain Ca 2+) hydrolyze starch, carbonic anhydrose (Zn 2+) breaks down carbonic acid, ascorbinotoxidase (Cu 2+) destroys vitamin C, etc.
2. NUCLEIC ACIDS
Nucleic acids were discovered in 1868. Swiss physician F. Mischer. The biological function of this substance remained unknown for almost a century, and only in the 40s of the last century Avery, MacLeod and McCarthy established that nucleic acids are responsible for storage, replication (reproduction), transcription (transmission) and translation (reproduction on protein) genetic (hereditary) information. In short, it is nucleic acids that determine the type, shape, chemical composition and functions of a living cell and the whole organism as a whole.
In 1953, Watson and Crick reported on the deciphering of the molecular structure of DNA. There are two types of nucleic acids in every living organism: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). At the same time, viruses contain only one type of nucleic acid: either RNA or DNA.
Nucleic acids are high molecular weight compounds that vary greatly in size. Molar mass the transport RNA is 25,000, while individual DNA molecules have a mass of 1,000,000 to 1,000,000,000.
The quantitative content of DNA in cells of one and the same organism is constant and is calculated by several picograms, however, in cells different types living organisms, there are significant quantitative differences in the DNA content. DNA is predominantly concentrated in the nucleus, mitochondria, and chloroplasts. RNA is mostly contained in the cytoplasm of cells. The RNA content is usually 5-10 times that of DNA. The RNA / DNA ratio in cells is the higher, the more intense the protein synthesis in them.
Nucleic acids are highly acidic and carry a high negative charge at physiological pH values. In this regard, in the cells of organisms, they easily interact with various cations and, first of all, with basic proteins, forming nucleoproteins.
Nucleic acid composition
Nucleic acids, when completely hydrolyzed, break down into three types of substances - nitrogenous bases (purine and pyrimidine bases), sugars (pentoses) and phosphoric acid.
The nucleic acid pentoses are represented by D-ribose or 2-D-deoxyribose. Both of these sugars are contained in the composition of nucleic acids in the furanose form and have the -configuration:
Nucleic acid is called ribonucleic acid (RNA) if it contains ribose, or deoxyribonucleic acid (DNA) if it contains deoxyribose. Recently, it was established that ribose and deoxyribose are not the only carbohydrates that make up nucleic acids: glucose has been found in a number of phage DNA and RNA of some types of cancer cells.
The nitrogenous bases that are commonly found in nucleic acids are purine derivatives adenine (A) and guanine (G) and pyrimidine derivatives cytosine (C ), thymine (T) and uracil (U). Purine and pyrimidine themselves are not included in the nucleic acids.
The structure of the main nitrogenous bases-components of nucleic acids:
Cytosine, adenine, guanine are found in both types of nucleic acids, uracil is only a part of RNA, and thymine is in DNA.
For guanine, cytosine, thymine, and uracil, keto-enol tautomerism is known; however, the keto structures are much more stable and dominate under physiological conditions.
Tautomerism
In nucleic acids, all oxo-containing nitrogenous bases are present in the keto form.
DNA and RNA contain so-called unusual or "minor" nitrogenous bases. These include, for example, 5-methylcytosine, 4-thiouracil, dihydrouracil, etc.
5-methylcytosine - thiouracil dihydrouracil
(in DNA) (in tRNA) (in tRNA)
The considered purine and pyrimidine bases, as well as some other derivatives of purine and pyrimidine, which are not part of nucleic acids, are often found in plants in significant amounts in a free state. Hypoxanthine (6-hydroxyoxypurine) found in the seeds of mustard and lupine is most often found in a free state in plants. Xanthine (2,6-dihydroxyoxypurine) and allontoin are very widespread in plants. In the form of these bases, as well as in the form of amino acid amides, nitrogen is stored and transported in plants.
hypoxanthine xanthine allantoin
Purines and pyrimidines absorb electromagnetic energy in the ultraviolet (UV) range, with each compound having a characteristic absorption spectrum, however, for all these compounds, the absorption maximum is observed near 260 nm. Nucleic acids also absorb in the UV region. Methods for the quantitative determination of nucleic acids are based on this property.
In the process of metabolism in animals and plants, purine bases form products such as uric acid, caffeine, theobromine, the latter are used as drugs.
Nucleosides
A nitrogenous base with a carbohydrate residue attached to it is called a nucleoside. In nucleosides, a covalent bond is formed by the C 1 -atom of the sugar and N 1 - a pyrimidine atom or N 9 - a purine atom, such a bond is called a glycosidic bond. To avoid confusion in numbering, the atoms of the carbohydrate part are distinguished by a prime. For the most common nucleosides, trivial names are adopted: adenosine, guanosine, uridine, and cytidine. Deoxyribonucleosides are called deoxyadenosine, deoxyguanosine, deoxycytidine, and thymidine.
For instance:
Pyrimidine Purine
ribonucleoside deoxyribonucleoside
Nucleosides are a fragment of the structure of nucleotides; however, many nucleosides are found in a free state. Some of them have medicinal properties. Various microorganisms secrete arabinosylcytosine and arabinosyladenin, which contain-D-arabinose instead of ribose. These substances are used as powerful antiviral and antifungal agents and against certain types of cancer. Mechanism of action of ara -A and ara -C is based on inhibition of DNA biosynthesis.
Nucleotides
Nucleotides are phosphorus esters of nucleosides. The 5 1 -carbon atom of pentose is involved in bond formation. Depending on the structure of the pentose, all nucleotides can be divided into ribonucleotides and deoxyribonucleotides.
Depending on the number of available phosphoric acid residues, nucleoside monophosphates, nucleoside diphosphates and nucleoside triphosphates are distinguished. All three types of nucleotides are constantly present in cells.
Figure 3 - mono-, di- and triphosphonucleotides (5 1) of adenosine.
The names of individual nucleotides are often denoted by abbreviated capital first letters of the names of the corresponding bases. Below are the nucleotides that make up the nucleic acids, and their abbreviations are given.
Table 2 - Abbreviated names of individual nucleotides
Nucleotides are strong acids, since the phosphoric acid residue in their composition is highly ionized.
The main function of nucleotides in a cell is that they are constituents of nucleic acids.
All nucleoside diphosphates and nucleoside triphosphates contain high-energy bonds (indicated by the “” symbol). During the hydrolysis of this bond, from 30 to 50 kJ / mol of energy is released, while during the hydrolysis of a conventional phosphate ester bond, an energy of 8-12 kJ / mol is released.
Under the influence of appropriate enzymes, phosphate groups containing high-energy bonds can be transferred to other substances. Thus, the energy accumulated in high-energy compounds can be used further in the metabolism. For example: ADP and ATP are involved in protein biosynthesis. Uridine diphosphate (U TF) and uridine diphosphate (U DP) are necessary for the action of enzymes that catalyze the conversion and synthesis of sugars (SDP and STF), cytidine diphosphate and cytidine triphosphate are involved in the biosynthesis of phospholipids.
Cyclic nucleotides were isolated in 1959. Sutherland (laureate Nobel Prize 1971) in the study of the mechanism of action of some hormones in the regulation of carbohydrate metabolism. In cyclic nucleotides, phosphoric acid binds two oxygen atoms of a pentose residue in the same nucleotide. There are three known cyclic nucleotides - cyclic adenosine monophosphate (with AMP), cyclic guanosine monophosphate (with G MF) and cyclic cytosine monophosphate (with CMP).
These nucleotides are formed from the corresponding nucleoside tri-phosphates by the action of the enzymes adenylate cyclase and guanylate cyclase. In biological processes, they act as an intermediate mediator for the regulatory action of hormones. acid... Structure proteins, functions proteins in the cell, amino acids. Nucleic acid... Lesson type - learning new material. ...
Protein, amino acids. Nucleic acid ATP, ADP, DNA self-doubling, RNA types
Lesson summary \u003e\u003e BiologyProtein, amino acids. Nucleic acid... ATP, ADP, self-doubling ... (ribose) - three phosphoric residues acidconnected by a macroergic bond. Refers to ... accompanied by the cleavage of 1-2 phosphoric residues acidwhich results in a discharge from ...
Protein, lipids and carbohydrates of viruses
Abstract \u003e\u003e ChemistrySpecific viral proteins and the process of self-assembly of these proteins from nucleic acid into new viral ... or when interacting with nucleic
Like proteins, nucleic acids are biopolymers, and their function is to store, implement, and transmit genetic (hereditary) information in living organisms.
There are two types of nucleic acids - deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleotides serve as monomers in nucleic acids. Each of them contains a nitrogenous base, a five-carbon sugar (deoxyribose in DNA, ribose in RNA) and a phosphoric acid residue.
DNA includes four types of nucleotides that differ in the nitrogenous base in their composition - adenine (A), guanine (G), cytosine (C) and thymine (T). The RNA molecule also contains 4 types of nucleotides with one of the nitrogenous bases - adenine, guanine, cytosine and uracil (U). Thus, DNA and RNA differ both in the content of sugar in the nucleotides and in one of the nitrogenous bases.
A DNA molecule can contain a huge number of nucleotides - from several thousand to hundreds of millions. Structurally, it is a double helix of polynucleotide chains, connected by hydrogen bonds between nitrogenous bases of nucleotides. Due to this, the polynucleotide chains are firmly held one next to the other.
RNA molecules are usually single-stranded (unlike DNA) and contain significantly fewer nucleotides.
The following nucleic acids are involved in protein biosynthesis:
1. DNA - it encodes a sequence of amino acid residues in a protein and serves as a template for the synthesis of mRNA.
2. Messenger RNA transfers information from DNA to ribosomes.
3. Ribosomal RNA - is a structural component of ribosomes, which are "machines" that collect protein from individual amino acids in strict accordance with the mRNA code.
4. Transport RNA - participates in codon recognition (three nucleotides per mRNA encoding 1 amino acid) and transports the required amino acids to the site of protein synthesis.
Proteins, unlike nucleic acids,
1) participate in the formation of the plasma membrane
2) are part of chromosomes
3) are accelerators of chemical reactions
4) carry out the transport function
5) perform a protective function
6) transfer hereditary information from the nucleus to the ribosome
Choose one answer: a. mitochondria and plastids b. plasma membrane c. shellless nuclear matter d. many large lysosomes The supply and movement of substances in the cell are involved Choose one or more answers: a. endoplasmic reticulum b. ribosomes c. liquid part of the cytoplasm d. plasma membrane e. centrioles of the cell center Ribosomes are Choose one answer: a. two diaphragm cylinders b. rounded membrane bodies c. microtubule complex d. two non-membrane subunits A plant cell, unlike an animal, has Choose one answer: a. mitochondria b. plastids c. plasma membrane d. Golgi apparatus Large molecules of biopolymers enter the cell through the membrane Choose one answer: a. by pinocytosis b. by osmosis c. by phagocytosis d. by diffusion When the tertiary and quaternary structure of the protein molecules in the cell is disrupted, they stop functioning Choose one answer: a. enzymes b. carbohydrates c. ATP d. lipids Question text
What is the relationship between plastic and energy metabolism
Choose one answer: a. energy metabolism supplies oxygen for plastic b. plastic metabolism supplies organic matter for energy c. plastic exchange supplies ATP molecules for energy d. plastic metabolism supplies minerals for energy
How many ATP molecules are stored during glycolysis?
Choose one answer: a. 38 b. 36 c. 4 d. 2
The reactions of the dark phase of photosynthesis involve
Choose one answer: a. molecular oxygen, chlorophyll and DNA b. carbon dioxide, ATP and NADPH2 c. water, hydrogen and tRNA d. carbon monoxide, atomic oxygen and NADP +
The similarity between chemosynthesis and photosynthesis is that in both processes
Choose one answer: a. solar energy is used to form organic matter b. the formation of organic substances uses the energy released during oxidation inorganic substances c. organic matter is formed from inorganic d. the same exchange products are formed
Information about the sequence of amino acids in a protein molecule is rewritten in the nucleus from a DNA molecule to a molecule
Choose one answer: a. rRNA b. mRNA c. ATP d. tRNA Which sequence correctly reflects the way the genetic information is realized Choose one answer: a. trait -\u003e protein -\u003e mRNA -\u003e gene -\u003e DNA b. gene -\u003e DNA -\u003e trait -\u003e protein c. gene -\u003e mRNA -\u003e protein -\u003e trait d. mRNA -\u003e gene -\u003e protein -\u003e trait
The whole set of chemical reactions in the cell is called
Choose one answer: a. fermentation b. metabolism c. chemosynthesis d. photosynthesis
The biological meaning of heterotrophic nutrition is
Choose one answer: a. consumption is not organic compounds b. synthesis of ADP and ATP c. obtaining building materials and energy for cells d. synthesis of organic compounds from inorganic
All living organisms in the process of life use energy that is stored in organic substances created from inorganic
Choose one answer: a. plants b. animals c. mushrooms d. viruses
In the process of plastic exchange
Choose one answer: a. more complex carbohydrates are synthesized from less complex b. fats are converted to glycerin and fatty acids c. proteins are oxidized to form carbon dioxide, water, nitrogen-containing substances d. energy is released and ATP is synthesized
The principle of complementarity underlies interaction
Choose one answer: a. nucleotides and the formation of a double-stranded DNA molecule b. amino acids and the formation of the primary structure of the protein c. glucose and the formation of a fiber polysaccharide molecule d. glycerol and fatty acids and the formation of fat molecules
The importance of energy metabolism in cellular metabolism is that it provides synthesis reactions
Choose one answer: a. nucleic acids b. vitamins c. enzymes d. ATP molecules
Enzymatic breakdown of glucose without the participation of oxygen is
Choose one answer: a. plastic exchange b. glycolysis c. preparatory stage exchange d. biological oxidation
The breakdown of lipids to glycerol and fatty acids occurs in
Choose one answer: a. oxygen stage of energy metabolism b. the process of glycolysis c. the course of plastic exchange d. preparatory stage energy exchange
Option 1 1. Give an example of the biocenotic level of life organization A) May lily of the valley B) Cod school C) Nucleic acid D) Pine forest 2.The largest systematic unit A) Kingdom B) Division C) Class D) Family 3. Eukaryotic cells include a cell A) Fungi B) Bacteria C) Cyanobacteria D) Viruses 4. Nitrogen base adenine, ribose and three phosphoric acid residues are part of A ) DNA B) RNA C) ATP D) protein 5. Ribosomes are A) A complex of microtubules B) A complex of two rounded membrane bodies C) Two membrane cylinders D) Two non-membrane subunits of a mushroom shape 6. A bacterial cell, like a plant cell, has A) Nucleus B) Golgi complex C) Endoplasmic reticulum D) Cytoplasm 7. Organoid, in which organic substances are oxidized to carbon dioxide and water A) Mitochondria B) Chloroplast C) Ribosome D) Golgi complex. 8. Chloroplasts in the cell do not perform the function of A) Synthesis of carbohydrates B) ATP synthesis C) Absorption of solar energy D) Glycolysis 9. Hydrogen bonds between CO and NH-groups in a protein molecule give it the shape of a spiral, which is characteristic of the structure of A) Primary B) Secondary C) Tertiary D) Quaternary 10. Unlike tRNA, mRNA molecules A) Deliver amino acids to the site of protein synthesis B) Serve as a matrix for tRNA synthesis C) Deliver hereditary information about the primary structure of the protein from the nucleus to the ribosome D) transfer enzymes to the assembly site of protein molecules. 11. The main source of energy in the cell A) Vitamins B) Enzymes C) Fats D) Carbohydrates 12. The process of primary synthesis of glucose takes place A) In the nucleus B) In chloroplasts C) Ribosomes D) Lysosomes 13. A source of oxygen released by cells during photosynthesis , is A) Water B) Glucose C) Ribose D) Starch 14. How many cells and with what set of chromosomes are formed after meiosis? 15. The divergence of chromatids to the poles of the cell occurs in A) Anaphase B) Telophase C) Prophase D) Metaphase 16. The biological meaning of mitosis. 17. Benefits of asexual reproduction.
Question 38. Nucleic acids and proteins
1. Functions of viral nucleic acids
2. Viral proteins
3. The processes of interaction of a virus with a cell of a macroorganism
1.Function of viral nucleic acidsregardless of their type is the storage and transmission of genetic information.Viral DNA can be linear (like in eukaryotes) or circular (like in prokaryotes), but unlike the DNA of both, it must be a single-stranded molecule. Viral RNAs have a different organization (linear, circular, fragmented, single-stranded and double-stranded), they are represented by plus or minus strands. Plus-threadsfunctionally identical to i-RNA, that is, they are able to translate the genetic information encoded in them to the ribosomes of the host cell.
Minus threadscannot function like i-RNA, and for the translation of the genetic information they contain, synthesis of the complementary plus-strand is required. RNA of plus-stranded viruses, in contrast to RNA of minus-stranded viruses, have specific formations necessary for recognition by ribosomes. In both double-stranded DNA and RNA viruses, information is usually recorded in only one strand, thereby saving genetic material. 2. Viral proteins by localization in virioneshare:
‣‣‣ capsid;
‣‣‣ proteins of the supercapsid membrane;
‣‣‣ genomic.
Capsid coat proteins in nucleocapsid viruses perform protective function -protect viral nucleic acid from adverse effects - and receptor (anchor) function, ensuring the adsorption of viruses on host cells and penetration into them.
Supercapsid coat proteins, like capsid coat proteins, perform protectiveand receptor function.These are complex proteins - lipo- and glycoproteins. Some of these proteins can form morphological subunits in the form of spiny processes and have the properties hemagglutinins(cause agglutination of red blood cells) or neyrami-nidases(destroy neuraminic acid, which is part of the cell walls).
A separate group is made up of genomic proteins, they covalently linkedwith the genome and form with the viral nucleic acid ribo- or deoxyribonucleoproteins. The main function of genomic proteins is participation in the replication of nucleic acid and the implementation of the genetic information contained in it, these include RNA-dependent RNA polymerase and reverse transcriptase.
Unlike proteins of the capsid and supercapsid membranes, these are not structural but functional proteins. All viral proteins also function as antigens, since they are products of the viral genome and, accordingly, foreign to the host organism. Kingdom representatives Viraaccording to the type of nucleic acid, they are divided into 2 subkingdoms - ribovirus and deoxyribovirus. Families, genera and species are distinguished in subkingdoms. Belonging of viruses to a particular family (there are 19 in total):
‣‣‣ the structure and structure of the nucleic acid;
‣‣‣ the type of nucleocapsid symmetry;
‣‣‣ the presence of a supercapsid shell. Belonging to a particular genus and species is associated with other biological properties of viruses:
‣‣‣ the size of virions (from 18 to 300 nm);
‣‣‣ the ability to reproduce in tissue cultures and chicken embryos;
‣‣‣ the nature of changes in cells under the influence of viruses;
‣‣‣ antigenic properties;
‣‣‣ ways of transmission;
‣‣‣ a circle of susceptible hosts.
Viruses - causative agents of human diseasesrefer to 6 DNAcontaining families (poxviruses, herpesviruses, hepadnaviruses, adenoviruses, papovaviruses, parvoviruses) and 13 families of RNA-containing viruses (reoviruses, togaviruses, flaviruses, coronaviruses, paramyxoviruses, orthomyxoviruses, rhabdoviruses-retroviruses, picovirus , filoviruses).
3. Interaction of a virus with a cell - this is a complex process, the results of which vary. On this basis(final result) can be distinguished 4 types of interaction between viruses and cells:
% / productive viral infection- this is a type of interaction between the virus and the cell, in which viruses reproduce, and the cell dies(for bacteriophages, this type of interaction with the cell is called lytic). A productive viral infection lies in the basis of acute viral diseases, as well as in the basis of conditional latent infections, in which not all cells of the affected organ die, but only a part, and the rest of the intact cells of this organ compensate for its functions, as a result of which the disease does not manifest itself for some time until decompensation occurs;
‣‣‣ abortive viral infection -this is a type of interaction between the virus and the cell, in which the reproduction of viruses does not occur, and the cell gets rid of the virus,at the same time, its functions are not violated, since this occurs only during the reproduction of the virus;
‣‣‣ latent viral infection -this is this type of virus interaction fromcage, in which both viruses and cellular components are reproduced, but the cell does not die;at the same time, cellular syntheses prevail, and in this regard, the cell retains its functions for a rather long time - this mechanism lies at the base of unconditioned latent viral infections;
‣‣‣ virus-induced transformations -this is a type of interaction between the virus and the cell, in which cells affected by the virus acquire new properties that were not previously inherent in them.The genome of the virus or part of it is integrated into the genome of the cell, and the viral genes are converted into a group of cellular genes. This viral genome integrated into the chromosome of the host cell is usually called provirus,and this state of cells is denoted as virogeny.
For any of the indicated types of interaction between viruses and cells, processes can be distinguished aimed at delivering viral nucleic acid into the cell, providing conditions andmechanisms of its replication and implementation of the genetic information contained in it.
Q 39.Features of the reproduction of viruses
1. Periods of productive viral infection
2. Virus replication
3. Broadcast
1.Productive viral infection carried out in 3 periods:
‣‣‣ initial periodincludes the steps of adsorption of the virus on the cell, penetration into the cell, disintegration (deproteinization) or "undressing" of the virus. The viral nucleic acid was delivered to the appropriate cellular structures and, under the action of lysosomal enzymes, the cells are freed from the protective protein membranes. As a result, a unique biological structure is formed: an infected cell contains 2 genomes (intrinsic and viral) and 1 synthetic apparatus (cellular);
‣‣‣ then starts second groupvirus reproduction processes, including middleand final periods,during which there is repression of the cellular and expression of the viral genome. Repression of the cellular genome is provided by low molecular weight regulatory proteins such as histones, synthesized in any cell. With a viral infection, this process intensifies, now the cell is a structure in which the genetic apparatus is represented by the viral genome, and the synthetic apparatus is represented by the synthetic systems of the cell.
2. The further course of events in the cell is directed on viral nucleic acid replication (synthesis of genetic material for new virions) and implementation of the genetic information contained in it (synthesis of protein components for new virions). In DNA-containing viruses, both in prokaryotic and eukaryotic cells, viral DNA replication occurs with the participation of cellular DNA-dependent DNA polymerase. In this case, single-stranded DNA-containing viruses first form complementarythread - the so-called replicative form, which serves as a matrix for daughter DNA molecules.
3. Realization of the genetic information of the virus contained in the DNA, happens as follows:with the participation of DNA-dependent RNA-polymerase, i-RNA are synthesized, which enter the ribosomes of the cell, where virus-specific proteins are synthesized. In double-stranded DNA viruses, the genome of which is transcribed in the cytoplasm of the host cell, this is its own genomic protein. Viruses whose genomes are transcribed in the nucleus of the cell use the cellular DNA-dependent RNA polymerase contained therein.
Have RNA virusesprocesses replicationtheir genome, transcription and translation of genetic information are carried out in other ways. Replication of viral RNAs, both minus and plus strands, is carried out through the replicative form of RNA (complementary to the original one), the synthesis of which is provided by RNA-dependent RNA polymerase, a genomic protein that all RNA-containing viruses have. The replicative form of RNA of minus-strand viruses (plus-strand) serves not only as a matrix for the synthesis of daughter molecules of viral RNA (minus-strands), but also performs the functions of i-RNA, i.e. goes to ribosomes and ensures the synthesis of viral proteins (broadcast).
Have plus-threadRNA-containing viruses perform the translation function by its copies, the synthesis of which is carried out through the replicative form (minus-strand) with the participation of viral RNA-dependent RNA polymerases.
Some RNA viruses (reoviruses) have a completely unique transcription mechanism. It is provided by a specific viral enzyme - revertase (reverse transcriptase)and is commonly called reverse transcription. Its essence is that, first, a transcript is formed on the viral RNA template with the participation of reverse transcription, which is a single strand of DNA. On it, with the help of cellular DNA-dependent DNA polymerase, the second strand is synthesized and a double-stranded DNA transcript is formed. From it, in the usual way, through the formation of i-RNA, the information of the viral genome is realized.
The result of the described processes of replication, transcription and translation is the formation daughter moleculesviral nucleic acid and viral proteins,encoded in the genome of the virus.
After that comes third, final periodinteractions of the virus and cells. New virions are assembled from the structural components (nucleic acids and proteins) on the membranes of the cytoplasmic reticulum of the cell. A cell whose genome has been repressed (suppressed) usually dies. Newly formed virions passively(as a result of cell death) or actively(by budding) leave the cell and end up in its environment.
Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, synthesis of viral nucleic acids and proteins and assembly of new virionsoccur in a certain sequence (dissociated in time) and in different structures of the cell (dissociated in space), in connection with which the method of reproduction of viruses was called disjunctive(disunited). In an abortive viral infection, the process of interaction of the virus with the cell is interrupted for one reason or another before the suppression of the cellular genome occurs. It is obvious that in this case genetic information the virus will not be realized and the reproduction of the virus does not occur, and the cell retains its functions unchanged.
With a latent viral infection in a cell, both genomes function simultaneously, and with virus-induced transformations, the viral genome becomes part of the cellular genome, functions and is inherited along with it.
Q 40.Culturing viruses in tissue cultures
1. Tissue culture characteristics
2. Cytopathic action of viruses
1.For the cultivation of viruses use a number of techniques.it cultivation of experimental animals in the organism,developing chicken vibrios and tissue cultures (more often embryonic tissues or tumor cells). To grow tissue culture cells, multicomponent nutrient media are used (medium 199, Eagle's medium, etc.). Οʜᴎ contain an indicator for measuring the pH of the medium and antibiotics to suppress possible bacterial contamination.
Tissue cultureare experiencingin which the viability of cells can be maintained only temporarily, and growing,in which cells not only maintain vital activity, but also actively divide.
IN rollertissue cultures are fixed on a dense base (glass) - more often in one layer (single-layer), and insuspended- weighed in a liquid medium. By the number of passages sustained by a growing tissue culture, among them are distinguished:
‣‣‣ primary(primary-trypsinized) tissue cultures that withstand no more than 5-10 passages;
‣‣‣ semi-transplantabletissue cultures that are supported in no more than 100 generations;
‣‣‣ transplantedtissue cultures that are maintained indefinitely innumerous generations.
Most often, single-layer primary transplantableand transplantable tissue cultures.
2. The multiplication of viruses in tissue culture can be judged by qi-topatic action (CPA):
‣‣‣ cell destruction;
‣‣‣ changing their morphology;
‣‣‣ formation of multi-core symplastsor synthiaas a result of cell fusion.
‣‣‣ In the cells of tissue culture during the multiplication of viruses, inclusions can form - structures that are not characteristic of normal cells.
Inclusions are detected in stained by Romanovsky-Giemsasmears from infected cells. Οʜᴎ are eosinophilicand basophilic.
By localization in the cagedistinguish between:
‣‣‣ cytoplasmic;
‣‣‣ nuclear;
‣‣‣ mixed inclusions.
Characteristic nuclear inclusions form in cells infected with herpes viruses (Caudry body),cytomegaly and polyoma, adenoviruses, and cytoplasmic inclusions - smallpox viruses (bodies of Guarnieri and Pashen),rabies (the little body of Babesha-Negri)and etc.
The multiplication of viruses in tissue culture can also be judged by the method of "plaques" (negative colonies). When viruses are cultured in a cell monolayer under an agar coating, in place of the affected cells, zones of destruction of monosom- so called sterile stainsor plaques.This makes it possible not only to determine the number of virions in 1 ml of medium (it is believed that one plaque is the offspring of one virion), but also to differentiate viruses among themselves by the phenomenon of plaque formation.
The next method, which makes it possible to judge the multiplication of viruses (only hemagglutinating) in tissue culture, can be considered hemadsorption reaction. When cultivating viruses with hemagglutting activity,excessive synthesis of hemagglutinins may occur. These molecules are expressed on the surface of tissue culture cells, and tissue culture cells acquire the ability to adsorb red blood cells on themselves - the phenomenon of hemadsorption.Hemagglutinin molecules also accumulate in the cultivation medium, which leads to the fact that the culture fluid (new virions accumulate in it) will acquire the ability to cause hemagglutination.
The most common method for assessing viral replication in tissue culture is method of "color test".When propagated in a nutrient medium with an indicator of uninfected
cells of tissue culture due to the formation of acidic metabolic products, it changes its color. During the reproduction of the virus, normal cell metabolism is disrupted, acidic products are not formed, the medium retains its original color.
Q 41.Antiviral defense mechanisms of macroorgan ism
/. Non-specific mechanisms
2. Specific mechanisms
3. Interferons
1. The existence of viruses in 2 (extracellularand intracellular) forms predetermineand features of immunity in viral infections.INthe same nonspecific and specific mechanisms of antimicrobial resistance operate in relation to extracellular viruses as in relation to bacteria. Cellular unresponsiveness - one of nonspecific protection factors.It is due lack of receptors on cellsfor viruses, making them immune to viral infection. The same group of protective factors include a febrile reaction, excretory mechanisms (sneezing, coughing, etc.). In defense against extracellular virus involved:
‣‣‣ complement system;
‣‣‣ properdin system;
‣‣‣ NK cells (natural killer cells);
‣‣‣ viral inhibitors.
Phagocytic defense mechanismineffective inagainst the extracellular virus, but enough active against cells already infected with the virus.Expression on the surface of such viral proteins makes them an object of macrophage phagocytosis. Since viruses are a complex of antigens, when they enter the body, an immune response develops and specific defense mechanisms are formed - antibodies and effector cells.
2. Antibodiesact only on the extracellular virus,preventing its interaction with the cells of the body and are ineffective against the intracellular virus. Some viruses (influenza virus, adenoviruses) are inaccessible to antibodies circulating in the blood serum and can persist in the human body for a long time, sometimes for life.
In viral infections, antibodies of the IgG and IgM classes are produced, as well as secretory antibodies of the IgA class. The latter provide local immunity of the mucous membranes at the entrance gate, which can be of decisive importance in the development of viral infections of the gastrointestinal tract and respiratory tract. Antibodies of the IgM class appear on the 3-5th day of illness and disappear after a few weeks, therefore their presence in the serum of the subject reflects acuteor freshly transferredinfection. Immunoglobulins G appear later and last longer than immunoglobulins M. Οʜᴎ are detected only 1-2 weeks after the onset of the disease and circulate in the blood for a long time, thereby providing protection against re-infection.
An even more important role than humoral immunity plays in all viral infections cellular immunity, which is due to the fact that cells infected with the virus become a target for cytolyticactions of T-killers. Among other things, a feature of the interaction of viruses with the immune system is the ability of some of them (the so-called lymphotropic viruses) directly affect the cells of the immune system, which leads to the development immunodeficiency states.
All of the listed "defense mechanisms (excluding phagocytosis of infected cells) are active only against the extracellular virus. Once in the cell, virions become inaccessible neither for antibodies, nor for complement, nor for other defense mechanisms. To protect against the intracellular virus during evolution, cells acquired the ability produce a special protein - interferon.
3. Interferon - this is a natural protein that has antiviral activity against intracellular forms of the virus.is he disrupts the translation of i-RNAon the ribosomes of cells infected with the virus, which leads to the cessation of viral protein synthesis. Proceeding from this universal mechanism of action, interferon suppresses the reproduction of any viruses, that is, it does not have specificity, the specificity of interferonin. It is of a specific nature, that is, human interferon inhibits the reproduction of viruses in human cells, mouse interferon inhibits the reproduction of mice, etc.
Interferon has and antitumor action,which is indirect evidence of the role of viruses in the occurrence of tumors. The formation of interferon in the cell begins already 2 hours after infection with the virus, i.e. much earlier than its reproduction, and is ahead of the mechanism antibody formation. Interferon is formed by any cellsbut its most active producers are leukocytes and lymphocytes. Currently, bacteria (Escherichia coli) have been created by genetic engineering methods, into the genome of which genes (or their copies) are introduced, which are responsible for the synthesis of interferon in leukocytes. The genetically engineered interferon thus obtained is widely used for the treatment and passive prevention of viral infections and some types of tumors. IN last years a wide range of drugs has been developed - inducers of endogenous interferon.Their use is preferable to the introduction exogenous interferon.Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, interferon is one of the important factors of antiviral immunity͵ but, unlike antibodies or effector cells, it provides not protein, but genetic homeostasis.
Q 42.Viral infections and methods for their diagnosis
1. Human viral infections
2. Laboratory diagnostics of viral infections
1.Today viral infections make up the predominant part of human infectious pathology.The most common among them remain acute respiratory infections (ARVI)and other viral infections transmitted by airborne droplets,whose pathogens belong to completely different families, most often they are RNA-containing viruses (influenza A, B, C virus, mumps virus, parainfluenza viruses, measles, rhinoviruses, etc.).
No less common are intestinal viral infectious diseases caused by viruses that also belong to different families of RNA and DNA viruses (enteroviruses, hepatitis A virus, rotaviruses, calicinoviruses, etc.).
Viral infectious diseases such as viral hepatitis,especially hepatitis B, transmitted by vector and sexually transmitted diseases. Their causative agents - hepatitis A, B, C, D, E, G, TT viruses - belong to different taxonomic groups (picornaviruses, hepadnaviruses, etc.), have different transmission mechanisms, but all have tropism for liver cells.
One of the most famous viral infections is HIV infection (often called AIDS - acquired immunodeficiency syndrome͵ which is its inevitable outcome). Human Immunodeficiency Virus (HIV) - the causative agent of HIV infection - belongs to the family of RNA viruses Retroviridae,the genus of lentiviruses.
Most of them - RNA containing,belong to the families -toga-, flavi-, bunyaviruses and are the causative agents of encephalitis and hemorrhagic fevers. The causative agents of severe forms of hemorrhagic fevers (Ebola, Marburg fever, etc.) are phylo-, adenoviruses. But the transmissible route of infection in these infectious diseases is not the only one. The above infections are mainly endemic diseases, but severe outbreaks of some of these diseases (Crimean hemorrhagic fever, West Nile fever) occurred in the Rostov and Volgograd regions in the summer of 1999 ᴦ.
In addition to infectious human pathology, the role of viruses in the development of some tumors of animals and humans has been proven. (oncogenic, or oncoviruses). Among the known viruses with oncogenic action, there are representatives of both DNA-containing (from the family of papovaviruses, herpes viruses, adenoviruses, poxviruses) and RNA-containing (from the family of retrorviruses, the genus of picornoviruses) viruses.
2. For laboratory diagnostics viral infections various methods are used.
Virological research (light microscopy)allows you to detect characteristic viral inclusions, and electron microscopy -the virions themselves and, according to the peculiarities of their structure, diagnose the corresponding infection (for example, rotavirus).
Virological research is aimed at virus isolation and identification.Infection of laboratory animals, chicken embryos or tissue culture is used to isolate viruses.
Primary identification of the isolated virus up to the family levelcan be done with:
‣‣‣ determining the type of nucleic acid (sample with bromodeoxyuridone);
‣‣‣ features of its structure (electron microscopy);
‣‣‣ virion size (filtration through membrane filters with pores 50 and 100 nm in diameter);
‣‣‣ the presence of a supercapsid shell (test with ether);
‣‣‣ hemagglutinins (hemagglutination reaction);
‣‣‣ type of symmetry nucleocapsid(electron microscopy).
The results are assessed by contamination of the tissue culture with an appropriately processed sample and then taking into account the results of contamination by a color filter sample. The study of viruses is also essential for identifying viruses (before the genus, species, within a species). antigenic structure,ĸᴏᴛᴏᴩᴏᴇ held in virus neutralization reactionswith the corresponding immune sera. The essence of this reaction is that after treatment with homologous antibodies, the virus loses its biological activity (neutralized) and the host cell develops in the same way as an uninfected virus. This is judged by the absence of cytopathic action, color test, the results of the hemagglutination inhibition reaction (RTGA), the absence of changes during infection of chicken embryos, and the survival rate of sensitive animals.
Virological research- this is "gold standard"virology and should be carried out in a specialized virological laboratory. It is used today
practically only in conditions of an epidemic outbreak of a viral infectious disease.
They are widely used for the diagnosis of viral infections immunodiagnostic methods (serodiagnostics and immunoindication). Οʜᴎ are realized in a wide variety of immune reactions:
‣‣‣ radioisotope immune analysis (RIA);
‣‣‣ enzyme immunoassay (ELISA);
‣‣‣ immunofluorescence reaction (REEF);
‣‣‣ complement fixation reaction (CSC);
‣‣‣ passive hemagglutination reaction (RPHA);
‣‣‣ reactions of inhibition of hemagglutination (RTGA), etc.
When using methods serodiagnosticsmandatory is study of paired sera.Wherein 4-fold increase in antibody titerin the second serum, in most cases, it serves as an indicator of an ongoing or freshly transferred infection. When examining one serum taken in the acute stage of the disease, the detection of antibodies of the class IgM,indicative of an acute infection.
A great achievement of modern virology is the introduction into the practice of diagnosing viral infections molecular genetic methods(DNA probing, polymerase chain reaction - PCR).First of all, with their help, persistent ^ viruses are detected that are in clinical material, hardly detectable or not detectable by other methods.
Q 43.Prevention and treatment of viral infections
1. Methods for the prevention of viral infections
2. Antiviral chemotherapy drugs
1. For active artificial prevention of viral infections. inincluding planned, widely used live viral vaccines. Οʜᴎ stimulate resistance at the site of the entrance gate of infection, the formation of antibodies and effector cells, as well as the synthesis of interferon. The main types of live viral vaccines:
‣‣‣ influenza, measles;
‣‣‣ poliomyelitis (Seibina-Smorodintseva-Chumakova);
‣‣‣ mumps, against rubella;
‣‣‣ antirabies, against yellow fever;
‣‣‣ genetically engineered vaccine against hepatitis B - Engerix B. To prevent viral infections used and killed vaccines:
‣‣‣ against tick-borne encephalitis;
‣‣‣ Omsk hemorrhagic fever;
‣‣‣ poliomyelitis (Salk);
‣‣‣ hepatitis A (Harviks 1440);
‣‣‣ antirabies (CDSV, Pasteur Merrier);
‣‣‣ as well as chemical - influenza.
For passive prevention andmmunotherapyproposed the following antibody preparations:
‣‣‣ anti-influenza gamma globulin;
‣‣‣ antirabies gamma globulin;
‣‣‣ measles gamma globulin for children under 2 years of age (in outbreaks) and for weakened older children;
‣‣‣ anti-influenza serum with sulfonamides.
Universal remedypassive prophylaxis of viral infections are interferon and endogenous interferon inducers.
2. Most known chemotherapy drugs do not have antiviralactivity,since the mechanism of action of most of them is based on suppressing microbial metabolism, and viruses do not have their own metabolic systems.
Antibiotics and sulfonamides for viral infections are used only for the purpose preventionbacterial complications. Nevertheless, currently being developed and applied chemotherapeutic agents with antiviral activity.
The first group - abnormal nucleosides.In structure, they are close to the nucleotides of viral nucleic acids, but included in the nucleic acid, they do not ensure its normal functioning. These drugs include azidothymidine, a drug that is active against the human immunodeficiency virus (HIV). The disadvantage of these drugs is their high toxicity for the cells of the macroorganism.
The second group of drugs disrupts the processes virus absorptionon the cells. Οʜᴎ less toxic, highly selective and very promising. These are thios-emicarbosone and its derivatives, acyclovir (zovirax) - herpes infection, remantadine and its derivatives - influenza A, etc.
Interferon is a universal means of therapy, as well as prevention of viral infections.
Question 38. Nucleic acids and proteins - concept and types. Classification and features of the category "Question 38. Nucleic acids and proteins" 2017, 2018.