For a detailed understanding of the essence of the PCR diagnostic method, it is necessary to make a short digression into the school biology course.
Even from school textbooks, we know that deoxyribonucleic acid (DNA) is a universal carrier of genetic information and hereditary traits in all organisms that exist on Earth. The only exceptions are some microorganisms, for example, viruses - their universal carrier of genetic information is RNA - single-stranded ribonucleic acid.
The structure of the DNA molecule
The discovery of the DNA molecule occurred in 1953. Francis Crick and James Watson discovered the structure of the DNA double helix, and their work was subsequently awarded the Nobel Prize.
DNA is a double strand twisted into a helix. Each strand consists of "bricks" - of sequentially connected nucleotides. Each DNA nucleotide contains one of the four nitrogenous bases - guanine (G), adenine (A) (purines), thymine (T) and cytosine (C) (pyrimidines), associated with deoxyribose, to the latter, in turn, a phosphate group is attached . Between themselves, adjacent nucleotides are connected in a chain by a phosphodiester bond formed by 3'-hydroxyl (3'-OH) and 5'-phosphate groups (5'-PO3). This property determines the presence of polarity in DNA, i.e., the opposite direction, namely the 5'- and 3'-ends: the 5'-end of one strand corresponds to the 3'-end of the second strand.
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DNA structure
The primary structure of DNA is the linear sequence of DNA nucleotides in a chain. The sequence of nucleotides in the DNA chain is written in the form of a DNA letter formula: for example - AGTCATGCCAG, the record is from the 5'- to the 3'-end of the DNA chain.
The secondary structure of DNA is formed due to the interactions of nucleotides (mostly nitrogenous bases) with each other, hydrogen bonds. A classic example of the secondary structure of DNA is the DNA double helix. The DNA double helix is the most common form of DNA in nature, consisting of two polynucleotide strands of DNA. The construction of each new DNA chain is carried out according to the principle of complementarity, i.e., each nitrogenous base of one DNA chain corresponds to a strictly defined base of the other chain: in a complementary pair, opposite A is T, and opposite G is C, etc.
Synthesis of DNA. replication
The unique property of DNA is its ability to duplicate (replicate). In nature, DNA replication occurs as follows: with the help of special enzymes (gyrazes), which serve as a catalyst (substances that accelerate the reaction), the helix is untwisted in the cell in the area where replication (doubling of DNA) should occur. Further, the hydrogen bonds that bind the threads are broken and the threads diverge.
In the construction of a new chain, a special enzyme, DNA polymerase, acts as an active “builder”. DNA duplication also requires a stratum block or "foundation", which is a small double-stranded DNA fragment. This starting block, or rather, the complementary section of the parent DNA chain, interacts with the primer, a single-stranded fragment of 20–30 nucleotides. DNA replication or cloning occurs simultaneously on both strands. Two DNA molecules are formed from one DNA molecule, in which one strand is from the parent DNA molecule, and the second, the daughter, is newly synthesized.
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Thus, the process of DNA replication (doubling) includes three main stages:
- Unwinding the DNA helix and separating the strands
- Attachment of primers
- Formation of a new DNA strand of a daughter strand
PCR analysis is based on the principle of DNA replication - DNA synthesis, which modern scientists have been able to artificially recreate: in the laboratory, doctors cause DNA doubling, but not the entire DNA chain, but its small fragment.
Functions of DNA
A human DNA molecule is a carrier of genetic information, which is written in the form of a sequence of nucleotides using the genetic code. As a result of the DNA replication described above, the transfer of DNA genes from generation to generation occurs.
Changes in the sequence of nucleotides in DNA (mutations) can lead to genetic disorders in the body.
At the end of the 19th century, an event occurred in Switzerland that determined the course of science for many decades to come: in the course of his research, the scientist F. Miescher discovered previously unknown molecules in lymphocytes.
The isolated molecules were subsequently found in all biological species and received the name under which they known today: "nucleic acids". The functions of nucleic acids in the cell are to store and transmit hereditary information.
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Nucleic acids are classified according to the presence in their composition of one of the varieties five-carbon sugar (pentose). Deoxyribonucleic acid, or DNA, contains deoxyribose, while ribonucleic acid (RNA) contains ribose.
Briefly, their interaction can be expressed as follows: RNA is synthesized from DNA, and protein is synthesized from RNA. There are many similarities in the structure of nucleic acids.
Let us analyze in more detail in which part of the cell nucleic acids are located, what functions they perform, what are the features of their structure and what types of nucleic acids exist.
DNA
The DNA molecule can be compared to a ladder that is twisted into a spiral towards the right. Steps or "lintels" on it formed by pairs of nitrogenous bases:
- adenine (A);
- guanine (G);
- thymine (T);
- cytosine (C).
Each base pairs with the other using the principle of complementarity, where adenine pairs exclusively with thymine (AT) and guanine pairs with cytosine (GC). Therefore, the randomness of the bonds between them is only apparent - the structure of nucleic acids subject to strict and unchanging laws.
Depending on the combinations of DNA nucleotides and the nitrogenous bases in them, our individual characteristics appear (color of skin, eyes, hair, height, etc.). DNA molecules are located in the nuclei of cells, as well as in chloroplasts and (less than 1%).
DNA molecule structure
A DNA molecule is a biopolymer, in which the main monomer or structural unit is a nucleotide. The following components are part of nucleotides: a phosphoric acid residue combines with a five-carbon sugar - deoxyribose and is built into a nitrogenous base. Between themselves, the monomers are combined into long chains, forming in end up double helix.
The helices are connected to each other by hydrogen bonds. Adenine combines with thymine with two, and cytosine with guanine with three hydrogen bonds. The nitrogenous base, sugar and phosphate group are mandatory in nucleotides.
The molecular width ranges from 2.2 to 2.4 nm, and the length of each monomer in the chain is 0.33 nm.
Each chain of deoxyribonucleic acid has a specific orientation. Two chains in opposite direction are called antiparallel.
Due to the principle of complementarity, all information in one chain is duplicated in another. The combination of adenine and guanine is a purine base, and thymine with cytosine is a pyrimidine base. In this case, it is necessary to know that in the DNA molecule the number of purine bases always equal to the number of pyrimidines.
DNA connection in gene transfer
We often hear accusations against genes when it comes to the bad tendencies and habits of a person. Let's try to figure out what genes are and what role DNA plays in transmission of hereditary data whether she carries negative information. What are the functions of nucleic acids in a cell?
A gene is a special section of the DNA molecule, formed from unique combinations of nucleotides. Each type of gene is located in a specially designated section of the DNA helix without migrating anywhere. The number of nucleotides in genes is constant. For example, the gene responsible for the synthesis of insulin has 60 base pairs in its composition.
Also in the DNA chain are the so-called. "non-coding sequences". Their role in the transfer of genetic material is not fully established. It is assumed that these sequences are responsible for the order in the work of genes and "twist" the chromosomes.
The entire volume of genes in the body is called. It, in turn, is evenly distributed in 46 pairs of DNA molecules. Each such pair is called a chromosome. Hence, The human body is made up of 46 pairs of chromosomes., in which all genetic information is embedded, from appearance to predisposition to various diseases.
Chromosomes differ in their morphology and size. There are two main forms - X and Y. The human body contains paired chromosomes, i.e. each has its exact copy. Thus, normally we have 23 paired chromosomes. Each chromosome pair performs its function, being responsible for specific features. 22 pairs of chromosomes are responsible for somatic characteristics and only one for sex. The combination of XX chromosomes means that a girl will be born, and the combination of XY means a boy.
DNA mutations
Damage to DNA molecules can be caused by many factors, among which most often have a mutagenic effect the following:
- Radiation. This is X-ray or ultraviolet radiation in high doses.
- Oxidant. These types of mutagens include all free radicals, nitric oxide and hydrogen peroxide.
- Carcinogenic. The factor is represented by an extensive list of substances, where the most common are benzopyrene, aflatoxin and ethidium bromide.
The vast majority of mutagens penetrate between two pairs of nitrogenous compounds, disrupting the structure of the nucleic acid molecule. The most dangerous inclusions of mutagenic components are double-stranded. Such disorders often lead to the death of entire fragments of chromosomes and various translocations.
Important! Human DNA is daily attacked by many aggressive factors that cause damage to the structure and break the helix itself. However, this molecule is distinguished by its ability to regenerate, which makes it possible to prevent mutations even at the stage of their formation.
RNA
The principle of the structure of RNA is fundamentally the same as the structure of DNA, but with the difference that ribonucleic acid is formed in the form of a single helix, in its composition thymine is replaced by uracil, and ribose takes the place of deoxyribose.
Due to the strictly sequential arrangement of nucleotides, RNA molecules are able to encode hereditary information.
However, unlike DNA, the functions of ribonucleic acids are different, more broad, due to the fact that there are three subtypes of molecules.
Types of RNA
There are 3 types of ribonucleic acid:
- Transport (tRNA). The tRNAs that make up the cytoplasm are the smallest molecules of ribonucleic acid. Their shape is similar to the shape of a clover leaf. tRNA is responsible for transporting specific amino acids directly to the site where protein synthesis occurs in order to initiate the formation of peptide bonds.
- Informational or matrix (mRNA, mRNA). It is part of the cell nucleus and cytoplasm. It transports information about the structure of a protein from DNA to ribosomes, which are the site of its biosynthesis.
- Ribosomal (rRNA). It is formed in the nucleolus and, as the name implies, is the main component of ribosomes. The largest type of RNA. Combines with messenger RNA to form protein
There is also a special kind. It is found in some viruses, bacteria and microorganisms. Acts simultaneously as tRNA and mRNA. Its main function is protein processing.
Structure of the RNA molecule
The structural formula of RNA is characterized by the presence of a hydroxyl group in the ribose position. Many types of ribonucleic acid, such as rRNA and mRNA, function in combination with proteins. Such compounds are called ribonucleotides.
The structure of the RNA nucleotide is similar to the structure of the DNA monomer. Nitrogenous bases also combine with each other according to the principle of complementarity. However, instead of thymine, uracil is present here, and the five-carbon sugar is represented by ribose.
Nucleotides in an RNA chain are connected via phosphodiester bonds.
protein synthesis
What substances can store information about the cell, its functions, biological and chemical properties? Of course, squirrels. They are unique components of any living organism. Biochemical protein synthesis is a rather complex microprocess. It goes through three main stages:
- Transcription. This process takes place in the nucleus, and information RNA is responsible for it. Transcription consists in reading data about the future protein from genes located in DNA and transferring this data to messenger RNA. The mRNA then transports the information to the cytoplasm. Deoxyribonucleic acid is not directly related to protein biosynthesis, but only stores and transmits information. During transcription, the DNA chains “unwind”, and the genetic material is read into RNA, taking into account paired complexes of nitrogenous bases.
- Broadcast. This is the final stage in the formation of a protein molecule. Messenger RNA enters the ribosomes through the cytoplasm, where the biochemical synthesis itself takes place.
- Various modifications of the polypeptide chain. Occur as a result of the completed translation.
DNA and RNA
Differences between DNA and RNA
Nucleic acids are characterized not only by similar, but also by distinctive features. Common signs include the following:
- Contains two base pairs.
- Responsible for the transmission of information.
- "Built" from nucleotide bonds, which are formed in accordance with the principle of complementarity.
- In the composition of a biological cell, both acids play a complementary role.
But considering both of these acids, significant differences can be found.
Curious facts
- The only cell type that does not contain DNA is red blood cells.
- The structure of nucleic acids is so similar that Western scientists have put forward the theory that in the early stages of the evolutionary history of mankind, the responsibility for storing information transmitted over inheritance, carried RNA.
- The structural formula of the DNA molecule was calculated by D. Utson and F. Crick back in 1953. And only 9 years later, these scientists were awarded the Nobel Prize in Medicine.
- Responsible for differences between people less than 1% of all DNA molecules included in the human genome. Therefore, the expression "we are all from the same test" has a scientific justification.
- The similarity between human and chimpanzee DNA reaches 98%, and human and pig DNA match 96%.
- Complete transcript of the human genome b was completed in 2003.
- It would take you 17 years to type the complete letter code of the human genome on a keyboard, given that you will have to tap the keys for days on end.
- human genome makes up 100% of the genes, of which 50% comes from the mother and 50% from the father.
Structure and functions of nucleic acids, biology lesson
How are DNA and RNA different
Conclusion
For almost two centuries, scientists have been trying to unravel all the secrets of tiny spirals, to completely decipher the structure of nucleic acids. But even to date, not all discoveries have been made that can shed light on these keepers of genetic information. Perhaps soon we will find out what else not the function known to us is performed by DNA.
To nucleic acids include high-polymer compounds that decompose during hydrolysis into purine and pyrimidine bases, pentose and phosphoric acid. Nucleic acids contain carbon, hydrogen, phosphorus, oxygen and nitrogen. There are two classes of nucleic acids: ribonucleic acids (RNA) and deoxyribonucleic acids (DNA).
Structure and functions of DNA
DNA- a polymer whose monomers are deoxyribonucleotides. The 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. Crick (to build this model, they used the work of M. Wilkins, R. Franklin, E. Chargaff).
DNA molecule formed by two polynucleotide chains, spirally twisted around each other and together around an imaginary axis, i.e. is a double helix (exception - some DNA-containing viruses have single-stranded DNA). The diameter of the DNA double helix is 2 nm, the distance between adjacent nucleotides is 0.34 nm, and there are 10 pairs of nucleotides per turn of the helix. The length of the molecule can reach several centimeters. Molecular weight - tens and hundreds of millions. The total length of DNA in the human cell nucleus is about 2 m. In eukaryotic cells, DNA forms complexes with proteins and has a specific spatial conformation.
DNA monomer - nucleotide (deoxyribonucleotide)- consists of residues of three substances: 1) a nitrogenous base, 2) a five-carbon monosaccharide (pentose) and 3) phosphoric acid. The nitrogenous bases of nucleic acids belong to the classes of pyrimidines and purines. Pyrimidine bases of DNA(have one ring in their molecule) - thymine, cytosine. Purine bases(have two rings) - adenine and guanine.
The monosaccharide of the DNA nucleotide is represented by deoxyribose.
The name of the nucleotide is derived from the name of the corresponding base. Nucleotides and nitrogenous bases are indicated by capital letters.
A polynucleotide chain is formed as a result of nucleotide condensation reactions. In this case, between the 3 "-carbon of the deoxyribose residue of one nucleotide and the phosphoric acid residue of the other, phosphoether bond(belongs to the category of strong covalent bonds). One end of the polynucleotide chain ends with a 5 "carbon (it is called the 5" end), the other ends with a 3 "carbon (3" end).
Against one chain of nucleotides is a second chain. The arrangement of nucleotides in these two chains is not random, but strictly defined: thymine is always located opposite the adenine of one chain in the other chain, and cytosine is always located opposite guanine, two hydrogen bonds arise between adenine and thymine, three hydrogen bonds between guanine and cytosine. The pattern according to which the nucleotides of different DNA strands are strictly ordered (adenine - thymine, guanine - cytosine) and selectively connect to each other is called the principle of complementarity. It should be noted that J. Watson and F. Crick came to understand the principle of complementarity after reading the works of E. Chargaff. E. Chargaff, having studied a huge number of samples of tissues and organs of various organisms, found that in any DNA fragment the content of guanine residues always exactly corresponds to the content of cytosine, and adenine to thymine ( "Chargaff's rule"), but he could not explain this fact.
From the principle of complementarity, it follows that the nucleotide sequence of one chain determines the nucleotide sequence of another.
DNA strands are antiparallel (opposite), i.e. nucleotides of different chains are located in opposite directions, and, therefore, opposite the 3 "end of one chain is the 5" end of the other. The DNA molecule is sometimes compared to a spiral staircase. The "railing" of this ladder is the sugar-phosphate backbone (alternating residues of deoxyribose and phosphoric acid); "steps" are complementary nitrogenous bases.
Function of DNA- storage and transmission of hereditary information.
Replication (reduplication) of DNA
- the process of self-doubling, the main property of the DNA molecule. Replication belongs to the category of matrix synthesis reactions and involves enzymes. Under the action of enzymes, the DNA molecule unwinds, and around each strand acting as a template, a new strand is completed according to the principles of complementarity and antiparallelism. Thus, in each daughter DNA, one strand is the parent strand, and the second strand is newly synthesized. This kind of synthesis is called semi-conservative.
The "building material" and source of energy for replication are deoxyribonucleoside triphosphates(ATP, TTP, GTP, CTP) containing three phosphoric acid residues. When deoxyribonucleoside triphosphates are included in the polynucleotide chain, two terminal residues of phosphoric acid are cleaved off, and the released energy is used to form a phosphodiester bond between nucleotides.
The following enzymes are involved in replication:
- helicases ("unwind" DNA);
- destabilizing proteins;
- DNA topoisomerases (cut DNA);
- DNA polymerases (select deoxyribonucleoside triphosphates and complementarily attach them to the DNA template chain);
- RNA primases (form RNA primers, primers);
- DNA ligases (sew DNA fragments together).
With the help of helicases, DNA is untwisted in certain regions, single-stranded DNA regions are bound by destabilizing proteins, and replication fork. With a discrepancy of 10 pairs of nucleotides (one turn of the helix), the DNA molecule must complete a complete revolution around its axis. To prevent this rotation, DNA topoisomerase cuts one DNA strand, allowing it to rotate around the second strand.
DNA polymerase can only attach a nucleotide to the 3" carbon of the deoxyribose of the previous nucleotide, so this enzyme is able to move along template DNA in only one direction: from the 3" end to the 5" end of this template DNA. Since the chains in maternal DNA are antiparallel , then on its different chains the assembly of the daughter polynucleotide chains occurs in different ways and in opposite directions. On the 3 "-5" chain, the synthesis of the daughter polynucleotide chain proceeds without interruption; this daughter chain will be called leading. On the chain 5 "-3" - intermittently, in fragments ( fragments of Okazaki), which, after completion of replication by DNA ligases, are fused into one strand; this child chain will be called lagging (lagging behind).
A feature of DNA polymerase is that it can start its work only with "seeds" (primer). The role of "seeds" is performed by short RNA sequences formed with the participation of the RNA primase enzyme and paired with template DNA. RNA primers are removed after the completion of the assembly of polynucleotide chains.
Replication proceeds similarly in prokaryotes and eukaryotes. The rate of DNA synthesis in prokaryotes is an order of magnitude higher (1000 nucleotides per second) than in eukaryotes (100 nucleotides per second). Replication begins simultaneously in several regions of the DNA molecule. A piece of DNA from one origin of replication to another forms a unit of replication - replicon.
Replication occurs before cell division. Thanks to this ability of DNA, the transfer of hereditary information from the mother cell to the daughter cells is carried out.
Reparation ("repair")
reparations is the process of repairing damage to the nucleotide sequence of DNA. It is carried out by special enzyme systems of the cell ( repair enzymes). The following steps can be distinguished in the process of DNA structure repair: 1) DNA-repairing nucleases recognize and remove the damaged area, resulting in a gap in the DNA chain; 2) DNA polymerase fills this gap by copying information from the second (“good”) strand; 3) DNA ligase “crosslinks” the nucleotides, completing the repair.
Three repair mechanisms have been studied the most: 1) photoreparation, 2) excise or pre-replicative repair, 3) post-replicative repair.
Changes in the structure of DNA occur constantly in the cell under the influence of reactive metabolites, ultraviolet radiation, heavy metals and their salts, etc. Therefore, defects in repair systems increase the rate of mutation processes and are the cause of hereditary diseases (xeroderma pigmentosa, progeria, etc.).
Structure and functions of RNA
is a polymer whose monomers are ribonucleotides. Unlike DNA, RNA is formed not by two, but by one polynucleotide chain (exception - some RNA-containing viruses have double-stranded RNA). RNA nucleotides are capable of forming hydrogen bonds with each other. RNA chains are much shorter than DNA chains.
RNA monomer - nucleotide (ribonucleotide)- consists of residues of three substances: 1) a nitrogenous base, 2) a five-carbon monosaccharide (pentose) and 3) phosphoric acid. The nitrogenous bases of RNA also belong to the classes of pyrimidines and purines.
The pyrimidine bases of RNA are uracil, cytosine, and the purine bases are adenine and guanine. The RNA nucleotide monosaccharide is represented by ribose.
Allocate three types of RNA: 1) informational(matrix) RNA - mRNA (mRNA), 2) transport RNA - tRNA, 3) ribosomal RNA - rRNA.
All types of RNA are unbranched polynucleotides, have a specific spatial conformation and take part in the processes of protein synthesis. Information about the structure of all types of RNA is stored in DNA. The process of RNA synthesis on a DNA template is called transcription.
Transfer RNAs usually contain 76 (from 75 to 95) nucleotides; molecular weight - 25,000-30,000. The share of tRNA accounts for about 10% of the total RNA content in the cell. tRNA functions: 1) transport of amino acids to the site of protein synthesis, to ribosomes, 2) translational mediator. About 40 types of tRNA are found in the cell, each of them has a nucleotide sequence characteristic only for it. However, all tRNAs have several intramolecular complementary regions, due to which tRNAs acquire a conformation that resembles a clover leaf in shape. Any tRNA has a loop for contact with the ribosome (1), an anticodon loop (2), a loop for contact with the enzyme (3), an acceptor stem (4), and an anticodon (5). The amino acid is attached to the 3' end of the acceptor stem. Anticodon- three nucleotides that "recognize" the mRNA codon. It should be emphasized that a particular tRNA can transport a strictly defined amino acid corresponding to its anticodon. The specificity of the connection of amino acids and tRNA is achieved due to the properties of the enzyme aminoacyl-tRNA synthetase.
Ribosomal RNA contain 3000-5000 nucleotides; molecular weight - 1,000,000-1,500,000. rRNA accounts for 80-85% of the total RNA content in the cell. In combination with ribosomal proteins, rRNA forms ribosomes - organelles that carry out protein synthesis. In eukaryotic cells, rRNA synthesis occurs in the nucleolus. rRNA functions: 1) a necessary structural component of ribosomes and, thus, ensuring the functioning of ribosomes; 2) ensuring the interaction of the ribosome and tRNA; 3) initial binding of the ribosome and the mRNA initiator codon and determination of the reading frame; 4) formation of the active center of the ribosome.
Information RNA varied in nucleotide content and molecular weight (from 50,000 to 4,000,000). The share of mRNA accounts for up to 5% of the total RNA content in the cell. Functions of mRNA: 1) transfer of genetic information from DNA to ribosomes, 2) a matrix for the synthesis of a protein molecule, 3) determination of the amino acid sequence of the primary structure of a protein molecule.
The structure and functions of ATP
Adenosine triphosphoric acid (ATP) is a universal source and main accumulator of energy in living cells. ATP is found in all plant and animal cells. The amount of ATP averages 0.04% (of the raw mass of the cell), the largest amount of ATP (0.2-0.5%) is found in skeletal muscles.
ATP consists of residues: 1) a nitrogenous base (adenine), 2) a monosaccharide (ribose), 3) three phosphoric acids. Since ATP contains not one, but three residues of phosphoric acid, it belongs to ribonucleoside triphosphates.
For most types of work occurring in cells, the energy of ATP hydrolysis is used. At the same time, when the terminal residue of phosphoric acid is cleaved, ATP is converted into ADP (adenosine diphosphoric acid), when the second phosphoric acid residue is cleaved, it becomes AMP (adenosine monophosphoric acid). The yield of free energy during the elimination of both the terminal and the second residues of phosphoric acid is 30.6 kJ each. Cleavage of the third phosphate group is accompanied by the release of only 13.8 kJ. The bonds between the terminal and the second, second and first residues of phosphoric acid are called macroergic (high-energy).
ATP reserves are constantly replenished. In the cells of all organisms, ATP synthesis occurs in the process of phosphorylation, i.e. addition of phosphoric acid to ADP. Phosphorylation occurs with different intensity during respiration (mitochondria), glycolysis (cytoplasm), photosynthesis (chloroplasts).
ATP is the main link between processes accompanied by the release and accumulation of energy, and processes that require energy. In addition, ATP, along with other ribonucleoside triphosphates (GTP, CTP, UTP), is a substrate for RNA synthesis.
Go to lectures №3“The structure and function of proteins. Enzymes»
Go to lectures number 5"Cell Theory. Types of cellular organization»
1. Select examples of the functions of proteins that they carry out at the cellular level of life.
1) provide transport of ions through the membrane
2) are part of the hair, feathers
3) form the skin
4) antibodies bind antigens
5) store oxygen in the muscles
6) ensure the work of the division spindle
2. Select the features of RNA.
1) found in ribosomes and nucleolus
2) capable of replication
3) consists of one chain
4) is contained in chromosomes
5) set of nucleotides ATHC
6) a set of nucleotides AGCU
3. What are the functions of lipids in the body of animals?
1) enzymatic
2) storage
3) energy
4) structural
5) contractile
6) receptor
4. What are the functions of carbohydrates in the body of animals?
1) catalytic
2) structural
3) storage
4) hormonal
5) contractile
6) energy
5. Proteins, unlike nucleic acids,
1) participate in the formation of the plasma membrane
2) are part of the chromosomes
3) participate in humoral regulation
4) carry out the transport function
5) perform a protective function
6) transfer hereditary information from the nucleus to the ribosome
6. Which of the following proteins cannot be found inside a muscle cell?
2) hemoglobin
3) fibrinogen
5) RNA polymerase
6) trypsin
7. Select the features of the structure of protein molecules.
1) are made up of fatty acids
2) consist of amino acids
3) the monomers of the molecule are held by peptide bonds
4) consist of monomers of the same structure
5) are polyhydric alcohols
6) the quaternary structure of molecules consists of several globules
8. Choose three functions that are unique to proteins.
1) energy
2) catalytic
3) motor
4) transport
5) structural
6) storage
9. What are the functions of carbohydrate and lipid molecules in the cell?
1) information
2) catalytic
3) construction
4) energy
5) storage
6) motor
10. All of the following chemical elements, except for two, are organogens. Identify two features that “fall out” of the general list, and write down in response the numbers under which they are indicated.
1) hydrogen
5) oxygen
11. All of the following chemical elements, except for two, are macronutrients. Identify two features that “fall out” of the general list, and write down in response the numbers under which they are indicated.
12. Choose THREE functions of DNA in a cell
1) an intermediary in the transfer of hereditary information
2) storage of hereditary information
3) amino acid coding
4) template for mRNA synthesis
5) regulatory
6) chromosome structuring
13. DNA molecule
1) a polymer whose monomer is a nucleotide
2) a polymer whose monomer is an amino acid
3) double-chain polymer
4) single chain polymer
5) contains hereditary information
6) performs an energy function in the cell
14. What are the characteristics of a DNA molecule?
1) consists of one polypeptide strand
2) consists of two polynucleotide strands twisted into a spiral
3) has a nucleotide containing uracil
4) has a nucleotide containing thymine
5) preserves hereditary information
6) transfers information about the structure of the protein from the nucleus to the ribosome
15. Monosaccharides in the cell perform the following functions:
1) energy
2) constituent components of polymers
3) information
4) constituent components of nucleic acids
5) protective
6) transport
16. How is an mRNA molecule different from DNA?
1) transfers hereditary information from the nucleus to the ribosome
2) the composition of nucleotides includes residues of nitrogenous bases, carbohydrate and phosphoric acid
3) consists of one polynucleotide strand
4) consists of two interconnected polynucleotide strands
5) it contains the carbohydrate ribose and the nitrogenous base uracil
6) it contains the carbohydrate deoxyribose and the nitrogenous base thymine
17. All of the features below, except for two, are functions of lipids. Identify two signs that “fall out” from the general list, and write down the numbers under which they are indicated in the table.
1) storage
2) hormonal
3) enzymatic
4) carrier of hereditary information
5) energy
18. All of the signs below, except for two, can be used to describe the importance of proteins in the human and animal body. Identify two features that “fall out” of the general list, and write down in response the numbers under which they are indicated.
1) serve as the main building material
2) are broken down in the intestine to glycerol and fatty acids
3) are formed from amino acids
4) converted to glycogen in the liver
5) as enzymes accelerate chemical reactions
19. All of the features listed below, except for two, can be used to describe the DNA molecule. Identify two signs that “fall out” from the general list, and write down the numbers under which they are indicated in the table.
4) capable of self-doubling
5) in complex with proteins forms chromosomes
20. All of the following features, except for two, can be used to determine the functions of lipids in the cell. Identify two signs that “fall out” from the general list, and write down the numbers under which they are indicated in the table.
1) storage
2) regulatory
3) transport
4) enzymatic
5) building
21. All of the features below, except for two, can be used to describe the functions of nucleic acids in a cell. Identify two features that “fall out” of the general list, and write down in response the numbers under which they are indicated.
1) carry out homeostasis
2) transfer hereditary information from the nucleus to the ribosome
3) participate in protein biosynthesis
4) are part of the cell membrane
5) transport amino acids
22. All of the features listed below, except for two, can be used to describe the DNA molecule. Identify two signs that “fall out” from the general list, and write down the numbers under which they are indicated in the table.
1) consists of two chains forming a spiral
2) contains ATHC nucleotides
3) contains ribose sugar
4) self-doubling
5) participates in the translation process
23. All but two of the features listed below can be used to describe the insulin molecule. Identify two signs that “fall out” from the general list, and write down the numbers under which they are indicated in the table
1) consists of amino acids
2) adrenal hormone
3) a catalyst for many chemical reactions
4) pancreatic hormone
5) a substance of protein nature
24 All but two of the following features can be used to describe egg white albumin. Identify two signs that “fall out” from the general list, and write down the numbers under which they are indicated in the table.
1) consists of amino acids
2) digestive enzyme
3) denatures reversibly when the egg is boiled
4) monomers are linked by peptide bonds
5) the molecule forms primary, secondary and tertiary structures
25. All of the features listed below, except for two, can be used to describe an RNA molecule. Identify two signs that “fall out” from the general list, and write down the numbers under which they are indicated in the table.
1) consists of two polynucleotide chains twisted into a spiral
2) transfers information to the site of protein synthesis
3) in complex with proteins builds the body of the ribosome
4) capable of self-doubling
5) transports amino acids to the site of protein synthesis
26. All but two of the features listed below can be used to describe the starch molecule. Identify two signs that “fall out” from the general list, and write down the numbers under which they are indicated in the table.
1) consists of one chain
2) highly soluble in water
3) in complex with proteins forms a cell wall
4) undergoes hydrolysis
5) is a reserve substance in muscle cells
Remember!
Why are nucleic acids classified as heteropolymers?
They consist of different monomers - nucleotides, but the nucleotides themselves differ in some structures.
What is a nucleic acid monomer?
Nucleotides
What functions of nucleic acids do you know?
Storage and transmission of hereditary information. DNA contains information about the primary structure of all proteins needed by the body. This information is recorded in a linear sequence of nucleotides. Since proteins play a primary role in the life of the body, participating in the structure, development, metabolism, it can be argued that DNA stores information about the body. In RNA, each of its types performs its function depending on its structure. mRNA is a copy of a DNA segment that contains information about the number, composition and sequence of amino acid residues that determine the structure and functions of a protein molecule. This RNA contains a plan for constructing a polypeptide molecule. tRNA - its role is to attach an amino acid molecule and transport it to the site of protein synthesis. rRNA - combines with a protein and forms special organelles - ribosomes, on which protein molecules are assembled in the cell of any living organism.
What properties of living things are determined directly by the structure and functions of nucleic acids?
Heredity, variability, reproduction
Review questions and assignments
1. What are nucleic acids? Why did they get such a name?
Nucleic acids are biopolymers whose monomers are nucleotides. From lat. "nucleos" - the nucleus, since these acids are located or synthesized in the nucleus, or in prokaryotes, the function of nuclear information is performed by the nucleoid (DNA or RNA).
2. What types of nucleic acids do you know?
DNA, RNA: i-RNA, t-RNA, r-RNA.
4. Name the functions of DNA. How are the structure and functions of DNA related?
Storage and transmission of hereditary information - DNA is located strictly in the nucleus.
The DNA molecule is capable of self-replication by doubling. Under the action of enzymes, the double helix of DNA unwinds, bonds between nitrogenous bases are broken.
DNA contains information about the primary structure of all proteins needed by the body. This information is recorded in a linear sequence of nucleotides.
Since proteins play a primary role in the life of the body, participating in the structure, development, metabolism, it can be argued that DNA stores information about the body.
5. What types of RNA exist in the cell, where are they synthesized? List their functions.
i-RNA, t-RNA, r-RNA.
i-RNA - synthesized in the nucleus on the DNA template, is the basis for protein synthesis.
tRNA is the transport of amino acids to the site of protein synthesis - to ribosomes.
rRNA - synthesized in the nucleoli of the nucleus, and forms the ribosomes themselves of the cell.
All types of RNA are synthesized on a DNA template.
6. Is it enough to know which monosaccharide is a part of nucleotides in order to understand what kind of nucleic acid we are talking about?
Yes, RNA contains ribose.
DNA contains deoxyribose.
Types of RNA will not be possible to recognize by one monosaccharide.
7. A fragment of one DNA chain has the following composition: A-G-C-G-C-C-C-T-A-. Using the principle of complementarity, complete the second strand.
A-G-C-G-C-C-C-T-A
T-C-G-C-G-G-G-A-T
Think! Remember!
1. Why are there three types of RNA molecules in cells, but only one type of DNA?
DNA is the largest molecule, it cannot leave the nucleus, the pores are too small. RNA is small molecules, each performs its own function, providing various functions in the cell, while working. On the DNA matrix, many types of RNA can be simultaneously synthesized, and all of them go to perform their functions.
3. What types of RNA will be the same in all organisms? Which type of RNA has the highest variability? Explain your point of view.
i-RNA and t-RNA will be the same in all organisms, since protein biosynthesis follows a single mechanism, and t-RNA carries the same 20 amino acids. rRNA may be different.
