Nucleic acids.

Nucleic acids (NA) were first discovered in 1869 by the Swiss biochemist Friedrich Miescher.

NAs are linear, unbranched heteropolymers, the monomers of which are nucleotides linked by phosphodiester bonds.

The nucleotide consists of:

nitrogenous base

Purines (adenine (A) and guanine (G) - their molecules consist of 2 rings: 5 and 6 membered),

Pyrimidine (cytosine (C), thymine (T) and uracil (U) - one six-membered ring);

carbohydrate (5-carbon sugar ring): ribose or deoxyribose;

phosphoric acid residue.

There are 2 types of NK: DNA and RNA. NKs provide storage, reproduction and implementation of genetic (hereditary) information. This information is encoded in the form of nucleotide sequences. The nucleotide sequence reflects the primary structure of proteins. The correspondence between amino acids and the nucleotide sequences encoding them is called genetic code. Unit genetic code DNA and RNA are triplet– a sequence of three nucleotides.

Types of nitrogenous bases	A, G, C, T	A, G, C, U
Types of pentoses	β,D-2-deoxyribose	β,D-ribose
Secondary structure	Regular, consists of 2 complementary chains	Irregular, some parts of one chain form a double helix
Molecular weight (number of nucleotide units in the primary chain) or from 250 to 1.2x10 5 kDa (kilodalton)	About thousands, millions	On the order of tens and hundreds
Localization in the cell	Nucleus, mitochondria, chloroplasts, centrioles	Nucleolus, cytoplasm, ribosomes, mitochondria and plastids
	Storage, transmission and reproduction of hereditary information over generations	Implementation of hereditary information

DNA (deoxyribonucleic acid) is a nucleic acid whose monomers are deoxyribonucleotides; it is the maternal carrier of genetic information. Those. all information about the structure, functioning and development of individual cells and the entire organism is recorded in the form of DNA nucleotide sequences.

The primary structure of DNA is a single-stranded molecule (phages).

The further arrangement of the polymer macromolecule is called the secondary structure. In 1953, James Watson and Francis Crick discovered the secondary structure of DNA - the double helix. In this helix, the phosphate groups are on the outside of the helices and the bases are on the inside, spaced at 0.34 nm intervals. The chains are held together by hydrogen bonds between the bases and are twisted around each other and around a common axis.

The bases in antiparallel strands form complementary (mutually complementary) pairs due to hydrogen bonds: A = T (2 connections) and G ≡ C (3 connections).

The phenomenon of complementarity in the structure of DNA was discovered in 1951 by Erwin Chargaff.

Chargaff's rule: the number of purine bases is always equal to the number of pyrimidine bases (A + G) = (T + C).

The tertiary structure of DNA is the further folding of a double-stranded molecule into loops due to hydrogen bonds between adjacent turns of the helix (supercoiling).

The quaternary structure of DNA is chromatids (2 strands of chromosome).

X-ray diffraction patterns of DNA fibers, first obtained by Morris Wilkins and Rosalind Franklin, indicate that the molecule has a helical structure and contains more than one polynucleotide chain.

There are several families of DNA: A, B, C, D, Z-forms. The B form is usually found in cells. All shapes except Z are right-handed spirals.

Replication (self-duplication) of DNA - This is one of the most important biological processes that ensure the reproduction of genetic information. Replication begins with the separation of two complementary strands. Each strand is used as a template to form a new DNA molecule. Enzymes are involved in the process of DNA synthesis. Each of the two daughter molecules necessarily includes one old helix and one new one. The new DNA molecule is absolutely identical to the old one in nucleotide sequence. This method of replication ensures accurate reproduction in daughter molecules of the information that was recorded in the mother DNA molecule.

As a result of the replication of one DNA molecule, two new molecules are formed, which are an exact copy of the original molecule - matrices. Each new molecule consists of two chains - one of the parent and one of the sister. This mechanism of DNA replication is called semi-conservative.

Reactions in which one heteropolymer molecule serves as a template (form) for the synthesis of another heteropolymer molecule with a complementary structure are called matrix type reactions. If during a reaction molecules of the same substance that serve as the matrix are formed, then the reaction is called autocatalytic. If, during a reaction, molecules of another substance are formed on the matrix of one substance, then such a reaction is called heterocatalytic. Thus, DNA replication (i.e. DNA synthesis on a DNA template) is autocatalytic reaction matrix synthesis.

Matrix type reactions include:

DNA replication (DNA synthesis on a DNA template),

DNA transcription (RNA synthesis on a DNA template),

RNA translation (protein synthesis on an RNA template).

However, there are other template-type reactions, for example, RNA synthesis on an RNA template and DNA synthesis on an RNA template. The last two types of reactions are observed when cells are infected with certain viruses. DNA synthesis on an RNA template ( reverse transcription) is widely used in genetic engineering.

All matrix processes consist of three stages: initiation (beginning), elongation (continuation) and termination (end).

DNA replication is a complex process in which several dozen enzymes take part. The most important of them include DNA polymerases (several types), primases, topoisomerases, ligases and others. The main problem with DNA replication is that in different chains of one molecule, phosphoric acid residues are directed in different directions, but chain extension can only occur from the end that ends with an OH group. Therefore, in the replicated region, which is called replication fork, the replication process occurs differently on different chains. On one of the strands, called the leading strand, continuous DNA synthesis occurs on a DNA template. On the other chain, which is called the lagging chain, binding occurs first primer– a specific fragment of RNA. The primer serves as a primer for the synthesis of a DNA fragment called fragment of Okazaki. Subsequently, the primer is removed, and the Okazaki fragments are stitched together into a single strand of the DNA ligase enzyme. DNA replication is accompanied reparation– correcting errors that inevitably arise during replication. There are many repair mechanisms.

Replication occurs before cell division. Thanks to this ability of DNA, hereditary information is transferred from the mother cell to the daughter cells.

RNA (ribonucleic acid) is a nucleic acid whose monomers are ribonucleotides.

Within one RNA molecule there are several regions that are complementary to each other. Hydrogen bonds are formed between such complementary regions. As a result, double-stranded and single-stranded structures alternate in one RNA molecule, and the overall conformation of the molecule resembles a clover leaf.

The nitrogenous bases that make up RNA are capable of forming hydrogen bonds with complementary bases in both DNA and RNA. In this case, nitrogenous bases form pairs A=U, A=T and G≡C. Thanks to this, information can be transferred from DNA to RNA, from RNA to DNA and from RNA to proteins.

There are three main types of RNA found in cells that perform different functions:

1. Information, or matrix RNA (mRNA, or mRNA). Function: protein synthesis matrix. Makes up 5% of cellular RNA. Transfers genetic information from DNA to ribosomes during protein biosynthesis. In eukaryotic cells, mRNA (mRNA) is stabilized by specific proteins. This makes it possible for protein biosynthesis to continue even if the nucleus is inactive.

mRNA is a linear chain with several regions with different functional roles:

a) at the 5" end there is a cap (“cap”) - it protects the mRNA from exonucleases,

b) it is followed by an untranslated region, complementary to the rRNA section, which is part of the small subunit of the ribosome,

c) translation (reading) of mRNA begins with the initiation codon AUG, encoding methionine,

d) the start codon is followed by a coding part, which contains information about the sequence of amino acids in the protein.

2. Ribosomal, or ribosomal RNA (rRNA). Makes up 85% of cellular RNA. In combination with protein, it is part of ribosomes and determines the shape of the large and small ribosomal subunits (50-60S and 30-40S subunits). They take part in translation - reading information from mRNA in protein synthesis.

Subunits and their constituent rRNAs are usually designated by their sedimentation constant. S - sedimentation coefficient, Svedberg units. The S value characterizes the sedimentation rate of particles during ultracentrifugation and is proportional to their molecular weight. (For example, prokaryotic rRNA with a sedimentation coefficient of 16 Svedberg units is designated 16S rRNA).

Thus, several types of rRNA are distinguished, differing in the length of the polynucleotide chain, mass and localization in ribosomes: 23-28S, 16-18S, 5S and 5.8S. Both prokaryotic and eukaryotic ribosomes contain 2 different high-molecular-weight RNAs, one for each subunit, and one low-molecular-weight RNA - 5S RNA. Eukaryotic ribosomes also contain low molecular weight 5.8S RNA. For example, prokaryotes synthesize 23S, 16S and 5S rRNA, and eukaryotes synthesize 18S, 28S, 5S and 5.8S.

80S ribosome (eukaryotic)

Small 40S subunit Large 60S subunit

18SrRNA (~2000 nucleotides), - 28SrRNA (~4000 nt),

5.8SpRNA (~155 nt),

5SpRNA (~121 nt),

~30 proteins. ~45 proteins.

70S ribosome (prokaryotic)

Small 30S subunit Large 50S subunit

16SpRNA, - 23SpRNA,

~20 proteins. ~30 proteins.

A large molecule of highly polymeric rRNA (sedimentation constant 23-28S, localized in the 50-60S ribosomal subunits.

A small molecule of high-polymer rRNA (sedimentation constant 16-18S, localized in 30-40S ribosomal subunits.

In all ribosomes without exception, low-polymer 5S rRNA is present and is localized in the 50-60S ribosomal subunits.

Low-polymer rRNA with a sedimentation constant of 5.8S is characteristic only of eukaryotic ribosomes.

Thus, ribosomes contain three types of rRNA in prokaryotes and four types of rRNA in eukaryotes.

The primary structure of rRNA is one polyribonucleotide chain.

The secondary structure of rRNA is the spiralization of the polyribonucleotide chain onto itself (individual sections of the RNA chain form helical loops - “hairpins”).

Tertiary structure of high-polymer rRNA - interactions of helical elements of secondary structure.

3. Transport RNA (tRNA). Makes up 10% of cellular RNA. Transfers the amino acid to the site of protein synthesis, i.e. to ribosomes. Each amino acid has its own tRNA.

The primary structure of tRNA is one polyribonucleotide chain.

The secondary structure of tRNA is a “cloverleaf” model, in this structure there are 4 double-stranded and 5 single-stranded regions.

The tertiary structure of tRNA is stable; the molecule folds into an L-shaped structure (2 helices almost perpendicular to each other).

All types of RNA are formed as a result of template synthesis reactions. In most cases, one of the DNA strands serves as the template. Thus, RNA biosynthesis on a DNA template is a heterocatalytic reaction of the template type. This process is called transcription and is controlled by certain enzymes - RNA polymerases (transcriptases).

RNA synthesis (DNA transcription) involves copying information from DNA to mRNA.

Differences between RNA synthesis and DNA synthesis:

Asymmetry of the process: only one DNA strand is used as a template.

Conservative process: the DNA molecule returns to its original state upon completion of RNA synthesis. During DNA synthesis, the molecules are half renewed, which makes replication semi-conservative.

RNA synthesis does not require any primer to begin, but DNA replication requires an RNA primer.

1. DNA doubling

2. rRNA synthesis

3. synthesis of starch from glucose

4. protein synthesis in ribosomes

3. Genotype is

1. set of genes in sex chromosomes

2. a set of genes on one chromosome

3. a set of genes in a diploid set of chromosomes

4. set of genes on the X chromosome

4. In humans, a recessive sex-linked allele is responsible for hemophilia. In the marriage of a woman who is a carrier of the hemophilia allele and a healthy man

1. the probability of giving birth to boys and girls with hemophilia is 50%

2. 50% of boys will be sick, and all girls are carriers

3. 50% of boys will be sick, and 50% of girls will be carriers

4. 50% of girls will be sick, and all boys are carriers

5. Sex-linked inheritance is the inheritance of characteristics that are always

1. appear only in males

2. appear only in sexually mature organisms

3. determined by genes located on sex chromosomes

4. are secondary sexual characteristics

In humans

1. 23 clutch groups

2. 46 clutch groups

3. one clutch group

4. 92 clutch groups

Carriers of the color blindness gene, in whom the disease does not manifest itself, may be

1. only women

2. only men

3. both women and men

4. only women with the XO set of sex chromosomes

In the human embryo

1. notochord, ventral nerve cord and gill arches are formed

2. notochord, gill arches and tail are formed

3. notochord and ventral nerve cord are formed

4. the ventral nerve cord and tail are formed

In the human fetus, oxygen enters the blood through

1. gill slits

4. umbilical cord

The twin research method is carried out by

1. crossing

2. Pedigree research

3. observations of research objects

4. artificial mutagenesis

8) Basics of immunology

1. Antibodies are

1. phagocyte cells

2. protein molecules

3. lymphocytes

4. cells of microorganisms that infect humans

If there is a risk of contracting tetanus (for example, if wounds are contaminated with soil), the person is given anti-tetanus serum. It contains

1. antibody proteins

2. weakened bacteria that cause tetanus

3. antibiotics

4. antigens of tetanus bacteria

Mother's milk provides the baby with immunity thanks to

1. macronutrients

2. lactic acid bacteria

3. microelements

4. antibodies

Enters the lymphatic capillaries

1. lymph from lymphatic ducts

2. blood from arteries

3. blood from veins

4. intercellular fluid from tissues

Phagocyte cells are present in humans

1. in most tissues and organs of the body

2. only in lymphatic vessels and nodes

3. only in blood vessels

4. only in the circulatory and lymphatic system

6. During which of the listed processes is ATP synthesized in the human body?

1. breakdown of proteins into amino acids

2. breakdown of glycogen to glucose

3. breakdown of fats into glycerol and fatty acid

4. oxygen-free oxidation of glucose (glycolysis)

7. In your own way physiological role most vitamins are

1. enzymes

2. activators (cofactors) of enzymes

3. an important source of energy for the body

4. hormones

Violation twilight vision and dry corneas may be a sign of vitamin deficiency

This special category chemical reactions occurring in the cells of living organisms. During these reactions, polymer molecules are synthesized according to the plan laid down in the structure of other polymer matrix molecules. An unlimited number of copy molecules can be synthesized on one matrix. This category of reactions includes replication, transcription, translation, and reverse transcription.

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Structure and functions of ATP nucleic acids

Nucleic acids include highly polymeric compounds that decompose during hydrolysis into purine and pyrimidine bases, pentose and phosphorus.. cell theory types of cell.. eukaryotic cell structure and functions of organelles..

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All topics in this section:

Structure and functions of DNA
DNA is a polymer whose monomers are deoxyribonucleotides. A model of the spatial structure of the DNA molecule in the form of a double helix was proposed in 1953 by J. Watson and F.

DNA replication (reduplication)
DNA replication is a process of self-duplication, the main property of the DNA molecule. Replication belongs to the category of matrix synthesis reactions and occurs with the participation of enzymes. Under the influence of enzyme

Structure and functions of RNA
RNA is a polymer whose monomers are ribonucleotides. Unlike DNA,

Structure and functions of ATP
Adenosine triphosphoric acid (ATP) is a universal source and main energy accumulator in living cells. ATP is found in all plant and animal cells. The amount of ATP in the medium

Creation and basic principles of cell theory
Cell theory- the most important biological generalization, according to which all living organisms are composed of cells. The study of cells became possible after the invention of the microscope. First

Types of Cellular Organization
There are two types of cellular organization: 1) prokaryotic, 2) eukaryotic. What is common to both types of cells is that the cells are limited by the membrane, the internal contents are represented by the cytop

Endoplasmic reticulum
Endoplasmic reticulum(ER), or endoplasmic reticulum (ER), is a single-membrane organelle. It is a system of membranes that form “cisterns” and channels

Golgi apparatus
The Golgi apparatus, or Golgi complex, is a single-membrane organelle. It consists of stacks of flattened “cisterns” with widened edges. Associated with them is the chalk system

Lysosomes
Lysosomes are single-membrane organelles. They are small bubbles (diameter from 0.2 to 0.8 microns) containing a set of hydrolytic enzymes. Enzymes are synthesized on rough

Vacuoles
Vacuoles are single-membrane organelles that are “containers” filled aqueous solutions organic and inorganic substances. EPS take part in the formation of vacuoles

Mitochondria
Mitochondria structure: 1 - outer membrane; 2 - internal membrane; 3 - matrix; 4

Plastids
Structure of plastids: 1 - outer membrane; 2 - internal membrane; 3 - stroma; 4 - thylakoid; 5

Ribosomes
Structure of the ribosome: 1 - large subunit; 2 - small subunit. Ribos

Cytoskeleton
The cytoskeleton is formed by microtubules and microfilaments. Microtubules are cylindrical, unbranched structures. The length of microtubules ranges from 100 µm to 1 mm, the diameter is

Cell center
Cell center includes two centrioles and a centrosphere. The centriole is a cylinder, the wall of which is formed by nine groups of t

Organoids of movement
Not present in all cells. Organelles of movement include cilia (ciliates, epithelium respiratory tract), flagella (flagellates, spermatozoa), pseudopods (rhizopods, leukocytes), myofibers

Structure and functions of the nucleus
As a rule, a eukaryotic cell has one nucleus, but there are binucleate (ciliates) and multinucleated cells (opaline). Some highly specialized cells are secondarily

Chromosomes
Chromosomes are cytological rod-shaped structures that represent condensed

Metabolism
Metabolism - most important property living organisms. The set of metabolic reactions occurring in the body is called metabolism. Metabolism consists of p

Protein biosynthesis
Protein biosynthesis is the most important process of anabolism. All characteristics, properties and functions of cells and organisms are ultimately determined by proteins. Squirrels are short-lived, their lifetime is limited

Genetic code and its properties
Genetic code is a system for recording information about the sequence of amino acids in a polypeptide by the sequence of nucleotides of DNA or RNA. Currently this recording system is considered

Eukaryotic gene structure
A gene is a section of a DNA molecule that encodes the primary sequence of amino acids in a polypeptide or the sequence of nucleotides in transport and ribosomal RNA molecules. DNA one

Transcription in eukaryotes
Transcription is the synthesis of RNA on a DNA template. Carried out by the enzyme RNA polymerase. RNA polymerase can only attach to a promoter that is located at the 3" end of the template DNA strand

Broadcast
Translation is the synthesis of a polypeptide chain on an mRNA matrix. The organelles that ensure translation are ribosomes. In eukaryotes, ribosomes are found in some organelles - mitochondria and plastids (7

Mitotic cycle. Mitosis
Mitosis is the main method of division of eukaryotic cells, in which duplication first occurs, and then uniform distribution between daughter cells hereditary material

Mutations
Mutations are persistent, sudden changes in the structure of hereditary material at various levels of its organization, leading to changes in certain characteristics of the organism.

Gene mutations
Gene mutations are changes in the structure of genes. Since a gene is a section of a DNA molecule, then gene mutation represents changes in the nucleotide composition of this site

Chromosomal mutations
These are changes in the structure of chromosomes. Rearrangements can be carried out both within one chromosome - intrachromosomal mutations (deletion, inversion, duplication, insertion), and between chromosomes - inter

Genomic mutations
A genomic mutation is a change in the number of chromosomes. Genomic mutations occur as a result of disruption of the normal course of mitosis or meiosis. Haploidy - y

Tertiary structure of RNA

Secondary structure of RNA

A ribonucleic acid molecule is made up of a single polynucleotide chain. Individual sections of the RNA chain form spiralized loops - “hairpins”, due to hydrogen bonds between complementary nitrogenous bases A-U and G-C. Parts of the RNA chain in such helical structures are antiparallel, but not always completely complementary; they contain unpaired nucleotide residues or even single-stranded loops that do not fit into the double helix. The presence of helical regions is characteristic of all types of RNA.

Single-stranded RNAs are characterized by a compact and ordered tertiary structure, which arises through the interaction of helical elements of the secondary structure. Thus, it is possible to form additional hydrogen bonds between nucleotide residues that are sufficiently distant from each other, or bonds between the OH groups of ribose residues and bases. The tertiary structure of RNA is stabilized by divalent metal ions, for example Mg 2+ ions, which bind not only to phosphate groups, but also to bases.

Matrix synthesis reactions produce polymers, the structure of which is completely determined by the structure of the matrix. Template synthesis reactions are based on complementary interactions between nucleotides.

Replication (reduplication, duplication of DNA)

Matrix– mother strand of DNA
Product– newly synthesized daughter DNA chain
Complementarity between the nucleotides of the mother and daughter DNA strands

The DNA double helix unwinds into two single strands, then the enzyme DNA polymerase completes each single strand into a double strand according to the principle of complementarity.

Transcription (RNA synthesis)

Matrix– DNA coding strand
Product– RNA
Complementarity between cDNA and RNA nucleotides

In a certain section of DNA, hydrogen bonds are broken, resulting in two single strands. On one of them, mRNA is built according to the principle of complementarity. Then it detaches and goes into the cytoplasm, and the DNA chains are again connected to each other.

Translation (protein synthesis)

Matrix– mRNA
Product- protein
Complementarity between the nucleotides of the mRNA codons and the nucleotides of the tRNA anticodons that bring amino acids

Inside the ribosome, tRNA anticodons are attached to the mRNA codons according to the principle of complementarity. The ribosome connects the amino acids brought by the tRNA together to form a protein.

7. Formation of a polypeptide chain from sequentially delivered to mRNA tRNA with corresponding amino acids occurs on ribosomes(Fig. 3.9).

Ribosomes are nucleoprotein structures that include three types of rRNA and more than 50 specific ribosomal proteins. Ribosomes consist of small and large subunits. Initiation of polypeptide chain synthesis begins with the attachment of the small ribosomal subunit to the binding center on mRNA and always occurs with the participation of a special type of methionine tRNA, which binds to the methionine codon AUG and attaches to the so-called P-site large ribosomal subunit.

Rice. 3.9. Synthesis of a polypeptide chain on a ribosome The transcription of mRNA and its transfer through the nuclear membrane into the cell cytoplasm are also shown.

Next mRNA codon, located after the AUG initiation codon, falls into the A region of the large subunit ribosomes, where it is “substituted” for interaction with amino-acyl-tRNA, which has the corresponding anticodon. After the appropriate tRNA has bound to the codon of the mRNA located in the A-site, a peptide bond is formed with the help of peptidyl transferase, which is part of the large subunit of the ribosome, and the aminoacyl-tRNA is converted into peptidyl-tRNA. This causes the ribosome to advance one codon, move the resulting peptidyl-tRNA to the P-site and release the A-site, which occupies the next codon of the mRNA, ready to combine with an aminoacyl-tRNA that has a suitable anticodon (Fig. 3.10).

The polypeptide chain grows due to repeated repetition of the described process. Ribosome moves along the mRNA, releasing its initiating site. At the initiation site, the next active ribosomal complex is assembled and the synthesis of a new polypeptide chain begins. Thus, several active ribosomes can join one mRNA molecule to form a polysome. Synthesis of the polypeptide continues until one of the three stop codons appears in the A region. The stop codon is recognized by a specialized termination protein, which stops synthesis and promotes the separation of the polypeptide chain from the ribosome and from mRNA.

Rice. 3.10. Synthesis of a polypeptide chain on a ribosome. A detailed diagram of the addition of a new amino acid to a growing polypeptide chain and the participation in this process of sections A and P of the large subunit of the ribosome.

Ribosome and mRNA also disconnect and are ready to begin a new synthesis of the polypeptide chain (see Fig. 3.9). It remains only to recall that proteins are the main molecules that ensure the vital activity of cells and organisms. They are enzymes that ensure the entire complex metabolism, and structural proteins that make up the skeleton of the cell and form intercellular substance, and transport proteins of many substances in the body, such as hemoglobin, which transports oxygen and channel proteins that ensure the penetration into and removal of various compounds from the cell.

a) The ribosomes of the granular EPS synthesize proteins that are then

Either they are removed from the cell (export proteins),
or are part of certain membrane structures (membranes themselves, lysosomes, etc.).

b) In this case, the peptide chain synthesized on the ribosome penetrates with its leader end through the membrane into the ER cavity, where the entire protein then ends up and its tertiary structure is formed.

2. Here (in the lumen of the EPS tanks) modification of proteins begins - binding them to carbohydrates or other components.

8. Mechanisms of cell division.

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1. Template synthesis reactions

In living systems, reactions occur that are unknown in inanimate nature - reactions of matrix synthesis.

The term “matrix” in technology refers to a mold used for casting coins, medals, and typographic fonts: the hardened metal exactly reproduces all the details of the mold used for casting. Matrix synthesis is like casting on a matrix: new molecules are synthesized in exact accordance with the plan laid down in the structure of existing molecules.

The matrix principle underlies the most important synthetic reactions of the cell, such as the synthesis of nucleic acids and proteins. These reactions ensure the exact, strictly specific sequence of monomer units in the synthesized polymers.

Here there is a directed contraction of monomers to a specific place in the cell - onto molecules that serve as a matrix where the reaction takes place. If such reactions occurred as a result of random collisions of molecules, they would proceed infinitely slowly. The synthesis of complex molecules based on the template principle is carried out quickly and accurately.

The role of the matrix in matrix reactions is played by macromolecules of nucleic acids DNA or RNA.

The monomeric molecules from which the polymer is synthesized - nucleotides or amino acids - in accordance with the principle of complementarity, are located and fixed on the matrix in a strictly defined, specified order.

Then the monomer units are “crosslinked” into a polymer chain, and the finished polymer is released from the matrix.

After this, the matrix is ​​ready for the assembly of a new polymer molecule. It is clear that just as on a given mold only one coin or one letter can be cast, so on a given matrix molecule only one polymer can be “assembled”.

Matrix reaction type -- specific feature chemistry of living systems. They are the basis of the fundamental property of all living things - its ability to reproduce its own kind.

Matrix synthesis reactions include:

1. DNA replication - the process of self-duplication of a DNA molecule, carried out under the control of enzymes. On each of the DNA strands formed after the rupture of hydrogen bonds, a daughter DNA strand is synthesized with the participation of the enzyme DNA polymerase. The material for synthesis is free nucleotides present in the cytoplasm of cells.

The biological meaning of replication lies in the accurate transfer of hereditary information from the mother molecule to the daughter molecules, which normally occurs during the division of somatic cells.

A DNA molecule consists of two complementary strands. These chains are held together by weak hydrogen bonds that can be broken by enzymes.

The molecule is capable of self-duplication (replication), and on each old half of the molecule a new half is synthesized.

In addition, an mRNA molecule can be synthesized on a DNA molecule, which then transfers the information received from DNA to the site of protein synthesis.

Information transfer and protein synthesis proceed according to the matrix principle, comparable to the work printing press in the printing house. Information from DNA is copied many times. If errors occur during copying, they will be repeated in all subsequent copies.

True, some errors when copying information with a DNA molecule can be corrected - the process of eliminating errors is called repair. The first of the reactions in the process of information transfer is the replication of the DNA molecule and the synthesis of new DNA chains.

2. transcription - synthesis of i-RNA on DNA, the process of removing information from a DNA molecule, synthesized on it by an i-RNA molecule.

I-RNA consists of a single chain and is synthesized on DNA in accordance with the rule of complementarity with the participation of an enzyme that activates the beginning and end of the synthesis of the i-RNA molecule.

The finished mRNA molecule enters the cytoplasm onto ribosomes, where the synthesis of polypeptide chains occurs.

3. translation - protein synthesis into mRNA; the process of translating the information contained in the nucleotide sequence of mRNA into the sequence of amino acids in the polypeptide.

4. synthesis of RNA or DNA from RNA viruses

Thus, protein biosynthesis is one of the types of plastic exchange, during which hereditary information encoded in DNA genes is implemented into a specific sequence of amino acids in protein molecules.

Protein molecules are essentially polypeptide chains made up of individual amino acids. But amino acids are not active enough to combine with each other on their own. Therefore, before connecting with each other and forming a protein molecule, amino acids must be activated. This activation occurs under the action of special enzymes.

As a result of activation, the amino acid becomes more labile and, under the action of the same enzyme, binds to t-RNA. Each amino acid corresponds to a strictly specific t-RNA, which finds “its” amino acid and transfers it to the ribosome.

Consequently, various activated amino acids enter the ribosome, connected to their tRNAs. The ribosome is like a conveyor for assembling a protein chain from various amino acids entering it.

Simultaneously with the t-RNA, on which its amino acid “sits,” the ribosome receives a “signal” from the DNA, which is contained in the nucleus. In accordance with this signal, one or another protein is synthesized in the ribosome.

The directing influence of DNA on protein synthesis is not carried out directly, but with the help of a special intermediary - matrix or messenger RNA (m-RNA or i-RNA), which is synthesized in the nucleus under the influence of DNA, so its composition reflects the composition of DNA. The RNA molecule is like a cast of the DNA form. The synthesized mRNA enters the ribosome and, as it were, conveys to this structure a plan - in what order the activated amino acids entering the ribosome should be connected to each other in order for a specific protein to be synthesized. Otherwise, the genetic information encoded in DNA is transferred to mRNA and then to protein.

The mRNA molecule enters the ribosome and stitches it. That segment of it that is in this moment in the ribosome, defined by a codon (triplet), interacts quite specifically with a triplet that matches it in structure (anticodon) in the transfer RNA, which brought the amino acid into the ribosome.

Transfer RNA with its amino acid approaches a specific codon of the mRNA and connects with it; another t-RNA with a different amino acid is added to the next neighboring section of i-RNA, and so on until the entire chain of i-RNA is read, until all the amino acids are reduced in the appropriate order, forming a protein molecule.

And the tRNA, which delivered the amino acid to a certain part of the polypeptide chain, is freed from its amino acid and leaves the ribosome. matrix cell nucleic gene

Then, again in the cytoplasm, the desired amino acid can join it and again transfer it to the ribosome.

In the process of protein synthesis, not one, but several ribosomes - polyribosomes - are involved simultaneously.

The main stages of the transfer of genetic information:

synthesis on DNA as an mRNA template (transcription)

synthesis of a polypeptide chain in ribosomes according to the program contained in mRNA (translation).

The stages are universal for all living beings, but the temporal and spatial relationships of these processes differ in pro- and eukaryotes.

In eukaryotes, transcription and translation are strictly separated in space and time: the synthesis of various RNAs occurs in the nucleus, after which the RNA molecules must leave the nucleus by passing through the nuclear membrane. The RNAs are then transported in the cytoplasm to the site of protein synthesis—ribosomes. Only after this comes the next stage - broadcasting.

In prokaryotes, transcription and translation occur simultaneously.

Thus, the place of synthesis of proteins and all enzymes in the cell are ribosomes - these are like protein “factories”, like an assembly shop, which receives all the materials necessary for assembling the polypeptide chain of protein from amino acids. The nature of the synthesized protein depends on the structure of i-RNA, on the order of arrangement of nucleoids in it, and the structure of i-RNA reflects the structure of DNA, so that ultimately the specific structure of the protein, i.e., the order of arrangement of various amino acids in it, depends on the order of arrangement nucleoids in DNA, from the structure of DNA.

The stated theory of protein biosynthesis is called matrix theory. This theory is called matrix because nucleic acids play the role of matrices in which all the information regarding the sequence of amino acid residues in a protein molecule is recorded.

The creation of the matrix theory of protein biosynthesis and deciphering the amino acid code is the largest scientific achievement XX century, the most important step towards elucidating the molecular mechanism of heredity.

Algorithm for solving problems.

Type 1. Self-copying of DNA. One of the DNA chains has the following nucleotide sequence: AGTACCGATACCTGATTTACG... What is the nucleotide sequence of the second chain of the same molecule? To write the nucleotide sequence of the second strand of a DNA molecule, when the sequence of the first strand is known, it is enough to replace thymine with adenine, adenine with thymine, guanine with cytosine, and cytosine with guanine. Having made such a replacement, we get the sequence: TACTGGCTTATGAGCTAAAATG... Type 2. Protein coding. The chain of amino acids of the ribonuclease protein has the following beginning: lysine-glutamine-threonine-alanine-alanine-alanine-lysine... What sequence of nucleotides does the gene corresponding to this protein begin with? To do this, use the genetic code table. For each amino acid, we find its code designation in the form of the corresponding triple of nucleotides and write it down. By arranging these triplets one after another in the same order as the corresponding amino acids, we obtain the formula for the structure of a section of messenger RNA. As a rule, there are several such triplets, the choice is made according to your decision (but only one of the triplets is taken). Accordingly, there may be several solutions. ААААААААЦУГЦГГЦУГЦГААГ Type 3. Decoding of DNA molecules. What sequence of amino acids does a protein begin with, if it is encoded by the following sequence of nucleotides: ACGCCCATGGCCGGT... Using the principle of complementarity, we find the structure of the section of messenger RNA formed on a given segment of the DNA molecule: UGCGGGUACCCGGCC... Then we turn to the table of the genetic code and for each triple of nucleotides, starting with the first, we find and write out the corresponding amino acid: Cysteine-glycine-tyrosine-arginine-proline-...

2. Notes on biology in grade 10 “A” on the topic: Protein biosynthesis

Purpose: To introduce the processes of transcription and translation.

Educational. Introduce the concepts of gene, triplet, codon, DNA code, transcription and translation, explain the essence of the process of protein biosynthesis.

Developmental. Development of attention, memory, logical thinking. Spatial imagination training.

Educational. Fostering a work culture in the classroom and respect for the work of others.

Equipment: Whiteboard, tables on protein biosynthesis, magnetic board, dynamic model.

Literature: textbooks Yu.I. Polyansky, D.K. Belyaeva, A.O. Ruvinsky; “Fundamentals of Cytology” O.G. Mashanova, “Biology” V.N. Yarygina, “Genes and Genomes” Singer and Berg, school notebook, N.D.Lisova studies. Manual for grade 10 “Biology”.

Methods and methodological techniques: story with elements of conversation, demonstration, testing.

	Test based on the material covered. Distribute sheets of paper and test options. All notebooks and textbooks are closed. 1 mistake with the 10th question completed is 10, with the 10th question not completed - 9, etc.
	Write down the topic of today's lesson: Protein biosynthesis. The entire DNA molecule is divided into segments that encode the amino acid sequence of one protein. Write down: a gene is a section of a DNA molecule that contains information about the sequence of amino acids in one protein.
	DNA code. We have 4 nucleotides and 20 amino acids. How can we compare them? If 1 nucleotide encoded 1 a/k, => 4 a/k; if there are 2 nucleotides - 1 a/k - (how many?) 16 amino acids. Therefore, 1 amino acid encodes 3 nucleotides - a triplet (codon). Count how many combinations are possible? - 64 (3 of them are punctuation marks). Enough and even in excess. Why excess? 1 a/c can be encoded with 2-6 triplets to increase the reliability of information storage and transmission. Properties of the DNA code. 1) The code is triplet: 1 amino acid encodes 3 nucleotides. 61 triplets encode a/k, with one AUG indicating the beginning of the protein, and 3 indicating punctuation marks. 2) The code is degenerate - 1 a/c encodes 1,2,3,4,6 triplets 3) The code is unambiguous - 1 triplet only 1 a/k 4) The code is not overlapping - from 1 to the last triplet the gene encodes only 1 protein 5) The code is continuous - there are no punctuation marks inside the gene. They are only between genes. 6) The code is universal - all 5 kingdoms have the same code. Only in mitochondria the 4 triplets are different. Think at home and tell me why?
	All information is contained in DNA, but DNA itself does not take part in protein biosynthesis. Why? The information is copied onto mRNA, and on it, in the ribosome, the synthesis of a protein molecule occurs. DNA RNA protein. Tell me if there are organisms that reverse order: RNA DNA?
	Biosynthesis factors: The presence of information encoded in a DNA gene. The presence of an messenger mRNA for transmitting information from the nucleus to ribosomes. Presence of an organelle - ribosome. Availability of raw materials - nucleotides and a/c Presence of tRNA to deliver amino acids to the assembly site Presence of enzymes and ATP (Why?)
	Biosynthesis process. Transcription.(show on model) Rewriting the nucleotide sequence from DNA to mRNA. The biosynthesis of RNA molecules proceeds to DNA according to the principles: Matrix synthesis Complementarities DNA and RNA The DNA is unlinked using a special enzyme, and another enzyme begins to synthesize mRNA on one of the strands. The size of mRNA is 1 or several genes. I-RNA leaves the nucleus through nuclear pores and goes to the free ribosome.
	Broadcast. Synthesis of polypeptide chains of proteins carried out on the ribosome. Having found a free ribosome, the mRNA is threaded through it. I-RNA enters the ribosome as a triplet AUG. Only 2 triplets (6 nucleotides) can be present in a ribosome at a time. We have nucleotides in the ribosome, now we need to somehow deliver the a/c there. Using what? - t-RNA. Let's consider its structure. Transfer RNAs (tRNAs) consist of approximately 70 nucleotides. Each tRNA has an acceptor end, to which an amino acid residue is attached, and an adapter end, which carries a triplet of nucleotides complementary to any codon of the mRNA, which is why this triplet is called an anticodon. How many types of tRNA are needed in a cell? T-RNA with the corresponding a/k tries to join the mRNA. If the anticodon is complementary to the codon, then a bond is added and formed, which serves as a signal for the movement of the ribosome along the mRNA strand by one triplet. The a/c attaches to the peptide chain, and t-RNA, freed from the a/c, enters the cytoplasm in search of another similar a/c. The peptide chain thus lengthens until translation ends and the ribosome jumps off the mRNA. One mRNA can contain several ribosomes (in the textbook, figure in paragraph 15). The protein chain enters the ER, where it acquires a secondary, tertiary or quaternary structure. The whole process is depicted in the textbook, Fig. 22 - at home, find the error in this picture - get 5) Tell me, how do these processes occur in prokaryotes if they do not have a nucleus?
	Regulation of biosynthesis. Each chromosome in linear order divided into operons consisting of a regulator gene and a structural gene. The signal for the regulator gene is either the substrate or the end products.
	1. Find the amino acids encoded in the DNA fragment. T-A-C-G-A-A-A-A-T-C-A-A-T-C-T-C-U-A-U- Solution: A-U-G-C-U-U-U-U-A-G-U-U-A-G-A-G-A-U-A- MET LEY LEY VAL ARG ASP It is necessary to compose a fragment of mRNA and break it into triplets. 2. Find the anticodons of the tRNA to transfer the indicated amino acids to the assembly site. Meth, three, hairdryer, arg.
	Homework paragraph 29.

The sequence of matrix reactions during protein biosynthesis can be represented as a diagram:

Option 1

1. The genetic code is

a) a system for recording the order of amino acids in a protein using DNA nucleotides

b) a section of a DNA molecule consisting of 3 neighboring nucleotides, responsible for the placement of a specific amino acid in a protein molecule

c) the property of organisms to transmit genetic information from parents to offspring

d) genetic information reading unit

40. Each amino acid is encoded by three nucleotides - this

a) specificity

b) triplet

c) degeneracy

d) non-overlapping

41. Amino acids are encrypted by more than one codon - this is

a) specificity

b) triplet

c) degeneracy

d) non-overlapping

42. In eukaryotes, one nucleotide is included in only one codon - this

a) specificity

b) triplet

c) degeneracy

d) non-overlapping

43. All living organisms on our planet have the same genetic code - this

a) specificity

b) universality

c) degeneracy

d) non-overlapping

44. The division of three nucleotides into codons is purely functional and exists only at the time of the translation process

a) code without commas

b) triplet

c) degeneracy

d) non-overlapping

45. Number of sense codons in the genetic code

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