Small molecules are biomolecules with a relatively low molecular weight from 100 to 1000, which contain up to 30 carbon atoms. Small molecules account for about 3% of the total cell mass.

Features of small molecules. They are located in a free state in the cytoplasm of the cell, due to which they can quickly move due to diffusion (on average, for a distance of 10 μm 0.2 s). Quite often they act as monomers: monomers of polysaccharides are monosaccharides, proteins - amino acids, nucleic acids - nucleotides. Monomers- simple molecules that are links in the chains of biopolymer macromolecules. they have the ability to polymerization, therefore, they contain groups that react with certain groups of other monomers to form covalent bonds... The combination of small molecules occurs by the removal of a water molecule during condensation reactions, and decay - as a result of a limited number of chemical transformations in those products from which they were synthesized. In molecules, certain simple combinations of atoms are repeatedly repeated - functional groups - chemical and physical properties of which determine the behavior of any molecules OH - hydroxyl group, NH2 - amino group, COOH - carboxyl group, etc.

Biological significance. The functions of small molecules in living organisms do not differ in variety, but they are very important for them. These are: 1) construction - participation in the formation of other, more complex molecules; 2) energy - participation in biochemical reactions of energy metabolism; 3) regulatory - participation in the regulation of processes and functions.

Variety of small molecules

The main families of small molecules include fatty acids, simple sugars, amino acids and nucleotides.

Monosaccharides (simple sugars ) - it is a group of carbohydrates, the molecules of which contain from three to ten carbon atoms. General formula monosaccharides - СnН2nОn. Content in the cell is about 1% of the total mass of the cell. With the same chemical composition, they can have a different order of bonds between atoms or groups of atoms, determines the existence structural isomers with different chemical properties(for example, glucose and fructose with the formula C6H12O6). By physical properties these are white crystalline substances, sweet in taste (fructose is sweet - 5 times sweeter than glucose), readily soluble in water, alcohols and insoluble in polar solvents. Due to the presence of several hydroxyl groups, they are capable of polymerization, form a large number of oligo- and polysaccharides, in which they are combined with the help of glycosidic bonds. They are synthesized from CO2 and water in the process of photosynthesis in plants and in the process of gluconeogenesis in animals. Decay is carried out by oxidation with the formation of CO2 and H2O with the release of a large amount of energy (for example, the oxidation of one glucose molecule is accompanied by the formation of 38 ATP molecules). In monosaccharides, there is a dependence of properties on the chemical composition, the spatial arrangement of groups, the ability to rotate the plane of polarized light, the presence and number of functional groups, etc. Monosaccharides can exist in two forms - linear, when the carbohydrate chain is open, and cyclical, when it is closed.

More than 50 different natural monosaccharides have already been described in the biochemistry of carbohydrates. The most common is their classification depending on the number of carbon atoms in the molecule, according to which the names of groups of monosaccharides form from the Greek name of the numeral, which corresponds to this number with the addition of an ending -ose(triose, tetrose, pentose, hexose, heptose, octose, nanose, decose). Pentoses and hexoses are of paramount importance in wildlife. Pentose is a group of monosaccharides whose molecules contain five carbon atoms. With pentose, ribose and deoxyribose are known, which are part of the ribonucleic (RNA) and deoxyribonucleic (DNA) acids, respectively. Hexoses - it is a group of monosaccharides whose molecules contain six carbon atoms. In nature, the most common are glucose and fructose, the content of which determines the sweet taste of berries and honey.

Distributed in organisms both in a free state and as part of oligosaccharides, polysaccharides, etc. important role in the metabolism involved in the processes of cellular respiration, fermentation and synthesis of complex carbohydrates. The main functions are energetic(when 1 g is broken down, 17.6 kJ of energy is released) and structures

tournaya(there are monomers of complex carbohydrates). Monosaccharide derivatives such as sugar alcohols (for example, mannitol in brown algae as a storage compound), sugar acids (ascorbic acid, uronic acids), glycosides (lily of the valley cardiac glycosides).

Fatty acid - it is a group of small organic molecules that are monobasic carboxylic acids by chemical nature. The general formula for fatty acids is CH3 - (CH2) n - COOH. There are two different parts in the molecule: a long hydrophobic carboxylic chain and a hydrophilic carboxyl group. Their content in the cell is about 1% of the total mass of the cell. Fatty acids differ in their melting point and solubility in water and organic solvents. An increase in the number of carbon atoms in molecules is accompanied by a decrease in water solubility and an increase in the melting point.

In water, their molecules can form a surface film or small micelles (particles in colloidal systems consisting of a hydrophobic core and a hydrophilic shell). Fatty acids combine with alcohols to form lipids using ester bonds. Their decomposition is carried out by oxidation with the formation of acetyl-CoA, CO2 and H2O with the release of a large amount of energy (for example, the oxidation of one palmitic acid molecule is accompanied by the formation of 130 ATP molecules). In fatty acids, there is a dependence of properties on the chemical composition, the presence of double bonds, etc.

By the number of carbon atoms, fatty acids are divided into inferior(up to 3 carbon atoms), average(4-9 carbon atoms) and higher(9-24 carbon atoms). By the peculiarities of the connections, there are saturated [NOT have double bonds) and unsaturated(can have one, two or more double bonds). The most common fatty acids are saturated fatty acids such as oil, palmitic, stearic, arachidic, and unsaturated fatty acids such as oleic, linoleic, linolenic, arachidonic.

Fatty acids are widespread in organisms both in a free state and in the composition of simple and complex lipids. But the most important manifestation of the structural function of fatty acids is participation in the construction of phospholipids cell membranes... Fatty acids are a valuable source of energy because their breakdown is accompanied by the release of twice as much energy as when the same mass of glucose breaks down. Unsaturated fatty acids ( linoleic, linolenic, arachidonic), which are conventionally combined into a group called "vitamin F", are involved in the processes of growth and development of the body, enhance defense reactions, and the like. The lack of this vitamin in the body of animals leads to the cessation of growth, causes dermatitis and diseases. internal organs... So, fatty acids are characterized by structural, energetic, and regulatory functions.

Amino acids are small organic molecules that include an amino group and a carboxyl group. Their content in the cell is 0.4% of the total cell mass. Their general formula includes a carboxyl group COOH, an amino group NH2 and a radical group, which is different in different amino acids and distinguishes them from each other. By physical power

Palmitic acid(C15H31COOH)

amino acids themselves are colorless crystalline substances, most of which are soluble in water. They may have a sweetish, bitter taste, a specific smell, but most have no taste or smell at all. All are thermally unstable. Amino acids are capable of polymerization, forming peptides and proteins. Most amino acids have one COOH (provides acidic properties) and one NH2 (provides basic properties), which together determine the amphoteric properties of amino acids. Due to the ability of the amino group and carboxyl group to ionize, ionic bonds, in the interaction of sulfhydryl groups (-SH) radicals of sulfur-containing amino acids are formed disulfide no bond, when hydrogen interacts with 0 or N in the composition of the OH or -NH groups, hydrogen bonds, and when NH2 of one amino acid interacts with COOH of another, with the release of water, peptide bonds . at an increase in pH, they act as donors of H + -ionites, and at a decrease, they act as acceptors of these ions, which indicates their ability to act as a buffer in solutions. In amino acids, there is a dependence of properties on the chemical composition, composition of radicals, the number of functional groups, pH on the action of polarized light, etc.

More than 200 amino acids have been isolated from natural sources. they are classified according to the structure of the radical, the number of functional groups, etc. According to their biological characteristics, amino acids are divided into replaceable(e.g. alanine, asparagine) and irreplaceable(leucine, valine). The former are synthesized in the body of humans and animals, while others are not synthesized and enter them only with food. For normal functioning, the body needs a complete set of 20 essential L-amino acids and certain additional amino acids, which are derived from the essential ones.

Essential amino acid names and abbreviations

Amino acid name	abbreviation	Variables (s) and constants (n)
		(C) - for children (n)
asparagine
aspartic acid
histidine		(C) - for children (n)
glutamine
glutamic acid
isoleucine
methionine
tryptophan
phenylalanine

The importance of amino acids is primarily due to the fact that they are protein monomers (structural function) and a source of energy (energy function). However, amino acids also have some specific functions. For example, the thyroid hormone thyroxine is synthesized from tyrosine.

Nucleotides - organic compounds, the molecules of which consist of a nitrogenous base, a monosaccharide and phosphoric acid residues. The content in the cell is 0.4% of the total cell mass. So, the composition of nucleotide molecules includes: 1) nitrogenous (nitrogen) base (A - adenine, or G - guanine, or T - thymine, or C - cytosine, or B - uracil) 2) carbohydrate, which are pentoses (ribose or deoxyribose) and phosphoric acid. The compound of the nitrogenous base from pentoses is called a nucleoside. Nucleotides are highly soluble in water. They are capable of polymerizing to form nucleic acids (RNA and DNA). They exhibit the properties of acids, since they contain phosphoric acid, and due to nitrogenous bases - basic properties. There are two types of covalent bonds in the composition of nucleotides: glycosidic(between nitrogenous base and pentose) and phosphoether(between pentose and phosphate residue).

Nucleotides combine into a polynucleotide chain to form a minucleotide 3 ", 5" -phosphodiester bond between the pentose of one nucleotide and the phosphate of the other. The nucleotides of the two strands are combined on the basis of the principle of structural complementarity by means of hydrogen bonds. The properties of nucleotides depend on the composition of nitrogenous bases, pentoses and the amount of phosphate residues.

Nucleotides are divided into ribonucleotides (adenyl, uridyl, guanyl, and cytidyl) and deoxyribonucleotides (adenyl, thymidyl, guanyl and cytidyl). Derivatives of nucleotides are nucleoside diphosphates(nucleotides with two phosphoric acid residues, for example, ADP, HDF), nucleoside triphosphates(nucleotides with three phosphoric acid residues, for example, ATP, GTP, TTF, CTP), NADF, NAD, FAD and dr.

Nucleotides are "building" subunits of nucleic acids, in combination with other groups form coenzymes in enzyme systems, for example, NADP, FAD ( structural function) , participate in energy exchange cells, for example, ATP ( energy function) , participate in the transmission of humoral signals into the cell, for example, cyclic AMP ( regulatory function) and etc.

Adenosine triphosphoric acid - an organic compound belonging to free nucleotides and is a universal chemical accumulator of energy in the cell. ATP molecule is a nucleotide that is composed of adenine, ribose and three phosphates. With the hydrolytic cleavage of the phosphate group from ATP, about 42 kJ of energy is released and ADP (adenosine diphosphoric acid) is formed. When two phosphates are cleaved from the ATP molecule, AMP (adenosine monophosphoric acid) is formed and 84 kJ of energy is released.

In the opposite process, when ATP is formed from ADP or AMP and inorganic phosphate, energy is accumulated in high-energy bonds that arise between the phosphoric acid residues. The processes of cleavage and formation of ATP occur constantly in accordance with the scheme:

So, the main function of ATP is energy, since it participates in energy metabolism, storing a significant amount of energy in its high-energy connections. In addition to the energetic function of ATP in cells, it is also a universal source of phosphate groups.

Most macromolecules can be combined into several classes: proteins, nucleic acids, carbohydrates, and lipids.

Encyclopedia "Avanta +"

55. What substances are synthesized in human cells from amino acids
A) phospholipids B) carbohydrates C) vitamins D) proteins

81. Monomers of molecules of what organic matter are amino acids
A) proteins B) carbohydrates C) DNA D) lipids

109. The formation of peptide bonds between amino acids in a protein molecule is based on
A) the principle of complementarity
B) insolubility of amino acids in water
C) the solubility of amino acids in water
D) the presence of carboxyl and amine groups in them

163. Enzymatic function in the cell is performed by
A) proteins
B) lipids
B) carbohydrates
D) nucleic acids

250. The synthesis of some simple organic substances in the laboratory has confirmed the possibility of abiogenic formation of proteins
A) amino acids
B) sugars
B) fats
D) fatty acids

364. Name the molecule that is part of the cell and has carboxyl and amino groups
A) Glucose
B) DNA
C) Amino acid
D) Fiber

439. Hydrogen bonds between CO and NH groups in a protein molecule give it a helical shape characteristic of the structure
A) primary
B) secondary
B) tertiary
D) quaternary

490. The secondary structure of a protein, in the form of a spiral, is held by bonds
A) peptide
B) ionic
B) hydrogen
D) covalent

550. Organic substances that accelerate metabolic processes -
A) amino acids
B) monosaccharides
C) enzymes
D) lipids

945. What connections determine the primary structure of protein molecules
A) hydrophobic between amino acid radicals
B) hydrogen between polypeptide strands
B) peptide between amino acids
D) hydrogen between -NH- and -CO- groups

984. The process of denaturation of a protein molecule is reversible, if the bonds are not destroyed
A) hydrogen
B) peptide
B) hydrophobic
D) disulfide

1075. The quaternary structure of a protein molecule is formed as a result of interaction
A) sections of one protein molecule by type S-S connections
B) several polypeptide filaments forming a ball
C) sections of one protein molecule due to hydrogen bonds
D) protein globule with a cell membrane

1290. The secondary structure of a protein molecule has the form
A) spirals
B) double helix
B) a ball
D) threads

1291. What is the function of proteins produced in the body when bacteria or viruses penetrate into it?
A) regulatory
B) signal
B) protective
D) enzymatic

1293. What is the function of proteins that accelerate chemical reactions in the cell
A) hormonal
B) signal
B) enzymatic
D) information

1312. Accelerate chemical reactions in the cell
A) enzymes
B) pigments
B) vitamins
D) hormones

2063. The primary structure of a protein is formed by a bond
A) hydrogen
B) macroergic
B) peptide
D) ionic

2065. The main function of enzymes in the body
A) catalytic
B) protective
B) storage
D) transport

2088. By their nature, enzymes belong to
A) nucleic acids
B) proteins
C) lipids
D) carbohydrates

2144. Destruction of the structure of a protein molecule is
A) denaturation
B) broadcast
C) reduplication
D) renaturation

2367. Speed chemical reactions in the cell, the proteins that perform the function
A) signal
B) humoral
B) catalytic
D) information

2420. Biocatalysts of chemical reactions in the human body are
A) hormones
B) carbohydrates
C) enzymes
D) vitamins

2483. Protective function in the body is performed by proteins that
A) carry out immune reactions
B) are capable of contraction
B) carry out oxygen transport
D) accelerate metabolic reactions

2504. The sequence and number of amino acids in a polypeptide chain is
A) the primary structure of DNA
B) the primary structure of the protein
C) secondary structure of DNA
D) secondary structure of protein

2562. Enzymatic, building, transport, protective functions in the cell are performed by molecules
A) lipids
B) carbohydrates
C) DNA
D) proteins

Option number 1

Objective 1.

A fragment of one of the chains of a DNA molecule has the following nucleotide sequence:

…A-G-T-A-C-C-G-A-T-A-C-G-A-T-T-T-A-C-G ...

What is the nucleotide sequence of the second strand of the same molecule?

Problem number 2.

Find and fix the error in the DNA molecule chain.

A-A-G-T-C-A-T-T-U-T-U-A

G-T-C-A-U-A-A-A-A-A-A

Test.

1. Hydrophobic compounds are

1) enzymes
2) proteins
3) polysaccharides
4) lipids

Explanation.

Hydrophobic substances are insoluble in water, primarily fats

(lipids)

Answer: 4

2. What substances are synthesized in human cells from amino acids

1) phospholipids
2) carbohydrates
3) vitamins
4) proteins

Explanation.

Proteins are synthesized from amino acids, carbohydrates consist of monosaccharides, phospholipids from glycerol and fatty acids, vitamins are of a different nature.

The correct answer is indicated under number: 4

Answer: 4

3. Monomers of molecules of which organic substances are amino acids

1) proteins
2) carbohydrates
3) DNA
4) lipids

Explanation.

Amino acids are part of proteins. Carbohydrates are made up of monosaccharides, DNA from nucleotides, lipids from glycerol and fatty acids.

Answer: 1

4. The enzymatic function in the cell is performed

1) proteins
2) lipids
3) carbohydrates
4) nucleic acids

Explanation.

Lipids are part of the membrane and participate in the selective permeability of membranes, carbohydrates are used for oxidation and the formation of ATP molecules, nucleic acids are stored and transmitted hereditary information, and proteins are included in the composition of enzymes, therefore, they perform an enzymatic function.

The correct answer is indicated under number: 1

Answer: 1

5. The synthesis of which simple organic substances in the laboratory confirmed the possibility of abiogenic formation of proteins

1) amino acids
2) sugars
3) fat
4) fatty acids

Explanation.

Proteins are made up of amino acids. If amino acids can be created abiogenically, proteins could be formed from them.

The correct answer is indicated under number: 1

Answer: 1

6. Ribose is part of the molecules

1) hemoglobin
2) DNA
3) RNA
4) chlorophyll

Explanation.

Ribose is a monosaccharide that is part of RNA.

Answer: 3

7. Name the molecule that is part of the cell and has carboxyl and amino groups

1) Glucose
2) DNA
3) Amino acid
4) Fiber

Explanation.

Amino and carboxyl groups contain amino acids.

The correct answer is indicated under number: 3

Answer: 3

8. Lipids dissolve in ether, but do not dissolve in water, since

1) consist of monomers
2) hydrophobic
3) hydrophilic
4) are polymers

Explanation.

Hydrophobic substances do not dissolve in water, and lipids are such substances.

Answer: 2

9. Hydrogen bonds between CO and NH groups in a protein molecule give it a spiral shape characteristic of the structure

1) primary
2) secondary
3) tertiary
4) quaternary

10. The helical secondary structure of the protein is held together by bonds

1) peptide
2) ionic
3) hydrogen
4) covalent

11. Water, which plays an important role in the entry of substances into the cell and the removal of waste products from it, performs the function

1) solvent
2) construction
3) catalytic
4) protective

1Explanation.

Water is the best solvent in the cell.

The correct answer is indicated under number: 1

Answer: 1

12. A significant part of the cell contents is water, which

1) forms a fission spindle
2) forms protein globules
3) dissolves fats
4) gives the cell elasticity

Explanation.

Water, filling the cell, gives it elasticity. The pressure of the cytoplasm acts on the cell wall. Fats are hydrophobic and do not dissolve in water. Protein globules are formed due to hydrogen bonds, disulfide bridges, ionic and hydrophobic interactions.

The correct answer is indicated under number: 4

Answer: 4

13. Living organisms need nitrogen, as it serves

1) the main constituent of proteins and nucleic acids
2) the main source of energy
3) the main structural component of fats and carbohydrates
4) the main oxygen carrier

14. Protein monomers are:

1) nucleotide

2) amino acid

3) glucose

4) glycerin

15. The sequence of monomers in a polymer is called:

1) primary structure

2) secondary structure

3) tertiary structure

4) quaternary structure

16. DNA is a polymer:

1) nonlinear

2) linear

3) checkered

4) branched

17. Iron is part of:

1) hemoglobin

2) erythromycin

3) insulin

4) wood

Test on the topic " Chemical composition cells. Nucleic acids".

Option number 2

Problem number 1

Specify the order of nucleotides in the DNA strand, formed by copying the strand:

C-A-C-C-G-T-A-A-C-G-G-A-T-C ...

What is the length and mass of the DNA chain? (The mass of one nucleotide is 345 cu)

Problem number 2

What is the molecular weight of a gene (two strands of DNA) if a protein with a molecular weight of 1500 c.u. is programmed in one of its strands?

Test.

1. Organic substances that accelerate metabolic processes -

1) amino acids
2) monosaccharides
3) enzymes
4) lipid

Explanation.

Enzymes are accelerators of processes in the cell.

The correct answer is indicated under number: 3

Answer: 3

2. ATP molecules perform a function in the cell

1) protective
2) catalytic
3) energy storage
4) transport of substances

Explanation.

ATP is an energy accumulator, the rest of the functions belong to proteins.

The correct answer is indicated under number: 3

Answer: 3

3. What connections determine the primary structure of protein molecules

1) hydrophobic between amino acid radicals
2) hydrogen between polypeptide strands
3) peptide between amino acids
4) hydrogen between -NH- and -CO- groups

Explanation.

The primary structure of a protein is determined by the sequence of amino acids that are interconnected peptide bonds.

The correct answer is indicated under number: 3

Answer: 3

4. The quaternary structure of a protein molecule is formed as a result of interaction

1) sections of one protein molecule by the type of S-S bonds
2) several polypeptide filaments forming a ball
3) sections of one protein molecule due to hydrogen bonds
4) a protein globule with a cell membrane

Explanation.

The quaternary structure of a protein is the number and arrangement of polypeptide chains. Proteins consisting of one polypeptide chain have only a tertiary structure (lysozyme, pepsin, myoglobin, trypsin), they are called monomers. For proteins consisting of several polypeptide chains, a quaternary structure is characteristic.

The correct answer is indicated under number: 2

Answer: 2

5. In the cell, lipids perform the function

1) catalytic
2) transport
3) information
4) energyExplanation.

1, 2 - functions of proteins, 3 - function of DNA, 4 - function of lipids and carbohydrates.

The correct answer is indicated under number: 4

Answer: 4

6. Human and animal cells use

1) hormones and vitamins
2) water and carbon dioxide
3) inorganic substances
4) proteins, fats and carbohydrates

Explanation.

Cell organelles are composed of proteins, fats and carbohydrates.

The correct answer is indicated under number: 4

Answer: 4

7. Fats, like glucose, perform a function in the cell

1) construction
2) information
3) catalytic
4) energy

Explanation.

A, C - functions of proteins, B - function of DNA, D - function of lipids and carbohydrates.

The correct answer is indicated under number: 4

Answer: 4

8. The secondary structure of a protein molecule has the form

1) spirals
2) double helix
3) tangle
4) threads

Explanation.

The primary structure is linear, the secondary is a spiral, and the coil is a tertiary structure.

The correct answer is indicated under number: 1

Answer: 1

9. What is the function of proteins produced in the body when bacteria or viruses enter it?

1) regulatory
2) signal
3) protective
4) enzymatic

Explanation.

Lymphocytes produce antibodies, which are proteins, so proteins have a protective function in the body.

The correct answer is indicated under number: 3

Answer: 3

10. Various functions in the cell are performed by molecules

1) DNA
2) proteins
3) mRNA
4) ATP

11. Minerals in the body are NOT involved in

1) building a skeleton
2) the release of energy through biological oxidation
3) regulation of cardiac activity
4) maintaining acid-base balanceExplanation.

Energy is released during the oxidation of glucose; minerals take part in all the other listed processes.

The correct answer is indicated under number: 2

Answer: 2

12. Water plays an important role in the life of the cell, as it

1) participates in many chemical reactions
2) ensures normal acidity of the environment
3) speeds up chemical reactions
4) is part of membranes

Explanation.

Water is a direct participant in many chemical processes in a cage. For example, it participates in the photolysis of water during photosynthesis.

The correct answer is indicated under number: 1

Answer: 1

13. Water participates in heat regulation due to

1) polarity of molecules
2) low heat capacity
3) high heat capacity
4) small molecule size

14 .Guanine refers to the grounds:

1) purine

2) pyrimidine

3) aniline

4) naphthalene

15. What is not included in DNA?

1) thymine

2) uracil

3) guanine

4) cytosine

16. Sucrose is:

1) polymer

2) monomer

3) dimer

4) cotton wool

17. Which of the following are polymers:

1) glucose

2) glycogen

3) cholesterol

4) DNA

5) hemoglobin

Test on the topic “The chemical composition of the cell. Nucleic acids".

Option number 3

Objective 1.

The molecular weights of four proteins are known:

A) 3000 USD; B) 4600 USD; C) 78000 USD; D) 3500 USD

Determine the lengths of the corresponding genes.

Objective 2.

A fragment of a DNA molecule contains 2348 nucleotides, including 420 adenine nucleotides. How many other nucleotides are there? Find the mass and length of the fragment and DNA?

1. Phospholipids are

1) enzymes responsible for the breakdown of fats
2) neurotransmitters synthesized by nerve cells
3) structural component cell membranes
4) storage substance of the cell

Explanation.

Phospholipids make up a double layer in the membrane and perform a structural function.

The correct answer is indicated under number: 3

Answer: 3

2. rRNA is

1) carrier of genetic information
2) a transporter of amino acids
3) component of the cell nucleus
4) component of ribosomes

Explanation.

mRNA is a carrier of genetic information, tRNA is a carrier of amino acids, DNA is a component of the nucleus, rRNA is a component of ribosomes.

The correct answer is indicated under number: 4

Answer: 4

3. A peptide bond occurs between

1) amino acids
2) glucose residues
3) water molecules
4) nucleotides

Explanation.

A peptide bond occurs between amino acids - that is, it occurs during the formation of proteins and peptides as a result of the interaction of the α-amino group (-NH2) of one amino acid with the α-carboxyl group (-COOH) of another amino acid

Between glucose residues and between nucleotides there is a covalent polar bond.

A hydrogen bond arises between water molecules. This chemical bond is intermolecular.

The correct answer is indicated under number: 1

Answer: 1

4. How many hydrogen bonds do adenine and thymine bond in a DNA molecule?

1) 1
2) 2
3) 3
4) 4

Explanation.

Hydrogen bonds between the nucleotides of two DNA strands: adenine-thymine (AT) - double; guanine-cytosine (G-C) - triple.

The correct answer is indicated under number: 2

Answer: 2

5. Signaling, motor, transport and protective functions in the cell are performed by

1) proteins
2) carbohydrates
3) lipids
4) DNA

Explanation.

The functions of proteins are varied.

- Building material - proteins are involved in the formation of the cell membrane, organelles and cell membranes. Blood vessels, tendons, and hair are built from proteins.

- Catalytic role - all cellular catalysts - proteins (active centers of the enzyme). The structure of the active site of the enzyme and the structure of the substrate match exactly like a key and a lock.

- Motor function - contractile proteins cause all movement.

- Transport function - the blood protein hemoglobin attaches oxygen and carries it to all tissues.

- The protective role is the production of protein bodies and antibodies to neutralize foreign substances.

- Energy function - 1 g of protein is equivalent to 17.6 kJ.

And if individually some of the listed functions may be inherent in both lipids and carbohydrates, then together - only proteins.

The correct answer is indicated under number: 1

Answer: 1

6. Protein secondary structure is maintained

1) covalent bonds
2) electrostatic interactions
3) hydrogen bonds
4) hydrophobic interactions

Explanation.

Secondary structure - local ordering of a fragment of the polypeptide chain, stabilized by hydrogen bonds.

The correct answer is indicated under number: 3

Answer: 3

7. Energy-rich bonds between phosphoric acid residues are present in the molecule

1) ATP
2) DNA
3) mRNA
4) squirrel

Explanation.

ATP - these connections are called macroenergetic, because when they break, 40 kJ of energy is released. ATP is adenosine phosphoric acid containing 3 phosphoric acid residues (or phosphate residues), serves as a universal carrier and the main accumulator of chemical energy in living cells

The correct answer is indicated under number: 1

Answer: 1

8. In the process of photosynthesis, the energy of light goes to the synthesis of molecules

1) DNA
2) proteins
3) fat
4) ATP

Explanation.

During the light phase, a quantum of light is absorbed by chlorophyll, resulting in the formation of ATP and NADPH molecules. In this case, water decomposes, forming hydrogen ions and releasing an oxygen molecule.

The correct answer is indicated under number: 4

Answer: 4

9. Outer plasma membrane proteins provide

1) transport of substances into the cell
2) oxidation of substances
3) its full permeability
4) elasticity and turgor of the cell

Explanation.

The main functions of the cell membrane (plasmalemma) are as follows: 1) barrier, 2) receptor, 3) exchange, 4) transport.

The membrane allows selective penetration into and from the cell into environment various chemicals. There are two main ways for substances to enter the cell and excreted from the cell to the external environment: passive transport, active transport.

With facilitated diffusion, proteins are involved in the transport of substances - carriers that work according to the "ping-pong" principle. In this case, the protein exists in two conformational states: in the "pong" state, the binding sites of the transported substance are open on the outside of the bilayer, and in the "ping" state, the same sites open on the other side. This process is reversible. Which side in this moment time will open the site of binding of the substance, depends on the concentration gradient of this substance.

In this way, sugars and amino acids pass through the membrane.

The correct answer is indicated under number: 1

Answer: 1

10. Enzymatic, building, transport, protective functions in the cell are performed by molecules

1) lipids
2) carbohydrates
3) DNA
4) proteins

11. Jonah what chemical element necessary for the blood clotting process?

1) sodium
2) magnesium
3) iron
4) calcium

12. In the process of blood clotting, calcium is one of the factors.

The correct answer is indicated under number: 4

Answer: 4

What property of water makes it a good solvent in biological systems?

1) high thermal conductivity
2) slow heating and cooling
3) high heat capacity
4) polarity of molecules

13. Explanation.

The water molecule is dipole, so it is a good solvent.

The correct answer is indicated under number: 4

Answer: 4

One of the elements that determine active ion transport across cell membranes is

1) potassium
2) phosphorus
3) iron
4) nitrogen

14. DNA does not include:

1) deoxyribose

2) adenine

3) uracil

4) phosphate

15 Select polymers from the following:

1) glucose

2) cellulose

3) cholesterol

4) RNA

5) hemoglobin

16. How many types of amino acids are in protein?

1) 12

2) 25

3) 20

4) as much as necessary

17 The proteins that make up chromosomes are called:

1) histones

2) protons

3) chromatin

4) Pinocchio

Answers to the testThe chemical composition of the cell. Nucleic acids » .

№ test

Option number 1

Option number 2

1,3

Option number 3

3

4

1

2

1

3

1

4

1

4

4

4

1

3

2,4,5

3

1

Protein Are biological heteropolymers, the monomers of which are amino acids. Proteins are synthesized in living organisms and perform certain functions in them.
Proteins contain atoms of carbon, oxygen, hydrogen, nitrogen and sometimes sulfur.

Protein monomers - amino acids - substances containing unchanged parts of the amino group NH2 and carboxyl group COOH and a variable part - a radical. It is by radicals that amino acids differ from each other. Amino acids have the properties of an acid and a base (they amphoteric), so they can connect with each other. Their number in one molecule can reach several hundred. The alternation of different amino acids in different sequences makes it possible to obtain a huge number of proteins with different structures and functions.

Found in proteins 20 types various amino acids, some of which animals cannot synthesize. They get them from plants that can synthesize all the amino acids. It is to amino acids that proteins are broken down in the digestive tracts of animals. From these amino acids entering the cells of the body, its new proteins are built.

Protein molecule structure - its amino acid composition, the sequence of monomers and the degree of twisting of the molecule, which should fit in various sections and organelles of the cell, and not one, but together with huge amount other molecules.

1.The sequence of amino acids in a protein molecule forms it primary structure. It depends on the sequence of nucleotides in the region of the DNA molecule (gene) that encodes a given protein. Adjacent amino acids are linked peptide connections arising between the carbon of the carboxyl group of one amino acid and the nitrogen of the amino group of another amino acid.
2.A long protein molecule folds up and at first takes the form of a spiral - secondary structure protein molecule. Between CO and NH - groups of amino acid residues of adjacent turns of the helix, there are hydrogen connections holding the chain.
3.A protein molecule of complex configuration in the form of a globule (ball), acquires tertiary structure ... The strength of this structure is ensured hydrophobic, hydrogen, ionic and disulfide S-S connections.
4 some proteins have quaternary structure , formed by several polypeptide chains (tertiary structures). The quaternary structure is also held by weak non-covalent bonds - ionic, hydrogen, hydrophobic.

However, the strength of these bonds is low and the structure can be easily broken. When heated or treated with some chemicals the protein is denatured and loses its biological activity.

Violation of the quaternary, tertiary and secondary structures is reversible. The destruction of the primary structure is irreversible.
Proteins have species specificity : Each type of organism has proteins that are not found in other species.

Table. Formation of structures (level of spatial organization) of proteins.

Protein functions .

Catalytic (enzymatic) - proteins accelerate all biochemical processes in the cell: the breakdown of nutrients in the digestive tract, participate in matrix synthesis reactions. Each enzyme accelerates one and only one reaction (both direct and reverse direction). The rate of enzymatic reactions depends on the temperature of the medium, the level of its pH, as well as on the concentrations of the reacting substances and the concentration of the enzyme.
Transport - proteins provide active transport of ions across cell membranes, oxygen transport and carbon dioxide, transport of fatty acids.
Protective - antibodies provide the body's immune defense; fibrinogen and fibrin protect the body from blood loss.
Structural - one of the main functions of proteins. Proteins are part of cell membranes; the protein keratin forms hair and nails; proteins collagen and elastin - cartilage and tendons.
Contractile - provided by contractile proteins - actin and myosin.
Signal - protein molecules can receive signals and serve as their carriers in the body (hormones). Remember that not all hormones are proteins.
Energy - with prolonged fasting, proteins can be used as additional source energy after carbohydrates and fats are used up.

Table. The main functions of proteins and peptides.

Thematic assignments.

Part A

A1... The sequence of amino acids in a protein molecule depends on:
1) gene structure
2) the external environment
3) their random combination
4) their structures

A2... A person obtains essential amino acids through
1) their synthesis in cells
3) taking medication
2) food intake
4) taking vitamins

A3... With a decrease in temperature, the activity of enzymes
1) increases markedly
2) decreases markedly
3) remains stable
4) changes periodically

A4... Participates in protecting the body from blood loss
1) hemoglobin
2) collagen
3) fibrin
4) myosin

A5... In which of these processes are proteins not involved?
1) metabolism
2) coding of hereditary information
3) enzymatic catalysis
4) transport of substances

A6... Give an example of a peptide bond:

Part B

IN 1... Choose functions specific to proteins
1) catalytic
2) hematopoietic
3) protective
4) transport
5) reflex
6) photosynthetic

IN 2.
Establish a correspondence between the structure of a protein molecule and its features

Part C

C1... Why is food stored in the refrigerator?
C2... Why do cooked foods last longer?
SZ... Explain the concept of "specificity" of a protein, and what biological significance has specificity?
C4... Read the text, indicate the numbers of the sentences in which mistakes were made and explain them.
1) Most of the chemical reactions in the body are catalyzed by enzymes.
2) Each enzyme can catalyze many types of reactions.
3) The enzyme has an active center, geometric shape which varies depending on the substance with which the enzyme interacts.
4) An example of the action of an enzyme can be the decomposition of urea by urease.
5) Urea decomposes into carbon dioxide and ammonia, which smells like a cat's litter box.
6) In one second, urease splits up to 30,000 urea molecules, under normal conditions it would take about 3 million years.

1. What substances are biological polymers? What substances are monomers for building biopolymer molecules?

a, d, f - are monomers; b, c, e - polymers

2. What functional groups are characteristic of all amino acids? What properties do these groups have?

Amino acid is an organic compound containing both an amino group (NH2), which is characterized by basic properties, and a carboxyl group (COOH) with acidic properties. Also, the amino acid contains a radical (R), it has a different structure for different amino acids, which gives different amino acids special properties.

3. How many amino acids are involved in the formation of natural proteins? What are the common structural features of these amino acids? How do they differ?

Only 20 are involved in the formation of natural proteins. Such amino acids are called protein-forming amino acids. Common structural features for them are the presence of an amino group and a carboxyl group, and the difference lies in various radicals.

4. How are amino acids linked to form a polypeptide chain? Build a dipeptide and a tripeptide. To complete the task, use structural formulas amino acids shown in the figure.

The amino group (–NH2) of one amino acid interacts with the carboxyl group (–СООН) of another amino acid, and a peptide bond arises between the nitrogen atom of the amino group and the carbon atom of the carboxyl group. The resulting molecule is a dipeptide with a free amino group at one end and a free carboxyl group at the other. Thanks to this, the dipeptide can attach other amino acids to itself, forming tripeptides, etc.

5. Describe the levels of the structural organization of proteins. What kind chemical bonds cause different levels of structural organization of protein molecules?

Protein molecules can take on various spatial forms, which represent four levels of their structural organization. 1) A chain of many amino acid residues connected by peptide bonds is the primary structure of a protein molecule. Other types of structures are created based on the primary structure. 2) The secondary structure of the protein arises as a result of the formation of hydrogen bonds between the hydrogen atoms of the NH-groups and the oxygen atoms of the CO-groups of different amino acid residues of the polypeptide chain. In this case, the polypeptide chain is twisted into a spiral. Hydrogen bonds are weak, but due to their significant amount, they ensure the stability of this structure. 3) The tertiary structure is formed due to the formation of hydrogen, ionic and other bonds that arise between different groups of atoms of a protein molecule in an aqueous medium. In some proteins, S S bonds (disulfide bonds) between cysteine ​​residues (an amino acid containing sulfur) play an important role in the formation of the tertiary structure. In this case, the polypeptide helix folds into a kind of coil (globule) in such a way that hydrophobic amino acid radicals are immersed inside the globule, while hydrophilic ones are located on the surface and interact with water molecules. 4) The molecules of some proteins include not one, but several polypeptides (globules) that form a single complex. This is how the quaternary structure is formed.

6. Humans and animals get amino acids from food. What can amino acids be synthesized in plants?

Autotrophic organisms synthesize all the amino acids they need from the primary products of photosynthesis and nitrogen-containing inorganic compounds.

7. How many different tripeptides can be built from three amino acid molecules (eg alanine, lysine and glutamic acid) if each amino acid can be used only once? Will these peptides have the same properties?

From these amino acids, 6 tripeptides can be built and each will have its own properties, since the amino acid sequence is different.

8. To separate a mixture of proteins into components, the method of electrophoresis is used: in an electric field, individual protein molecules move at a certain speed to one of the electrodes. In this case, some proteins move towards the cathode, while others move towards the anode. How is the structure of a protein molecule related to its ability to move in an electric field? What determines the direction of movement of protein molecules? What determines their speed?

The charge of a protein molecule depends on the ratio of acidic and basic amino acid residues. The carboxyl group and the amino group acquire different charges (negative and positive) due to the fact that in aqueous solutions the carboxyl group dissociates into COO– + H + and has negative charge, and the amino group is positive due to the addition of hydrogen ions. As a result, a total charge is formed, which determines the movement of the protein molecule. If acidic amino acid residues predominate, the molecule has a negative charge and moves towards the anode, but if basic amino acid residues predominate, the molecule has a positive charge and moves towards the cathode. The speed of movement depends on the amount of charge, the mass of the protein and the spatial configuration.