Proteins are the highest form of organization of matter at the molecular level. There is not a single process or structure in which proteins would not be involved. Their functions are diverse and at the same time universal. Not without reason in science they say that life is a way of existence of protein bodies.

The links of proteins are amino acids, which got their name because they consist of an amino group, which determines the alkaline properties, and an acid group.

There are several types of "packaging" of proteins in space.

Primary Structure is a chain with a specific amino acid sequence.

In a living cell, protein molecules have helical sections. It's nothing but secondary structure.

Tertiary structure- a squirrel thread laid in a certain way in space. In this case, the spiral usually takes the form of a globe or a ball.

AT quaternary structure proteins are stacked that have two or more chains that are different in their primary structure.

Protein functions. Table

Functions	Role
construction	from the amino acids supplied from the outside, the proteins inherent in this organism are synthesized
structural	proteins are part of all cellular organelles
synthesis (catalytic)	proteins act as enzymes
regulating (hormonal)	hormones monitor the activity of enzymes, control biophysiological processes
protective (immunological)	when microbes enter the bloodstream, antibodies, immunoglobulins are produced
energy	with a small amount of fats or carbohydrates, protein molecules are destroyed, releasing energy
signal (identification)	proteins embedded on the membrane surface are able to change their coordination in space in response to external factors
receptor	each hormone and physiologically active compound has its own receptor
transport	proteins can attach to various substances and deliver them from one compartment of the cell to another
motor	proteins are responsible for muscle contraction, etc. myofibrils are contractile proteins
biocomplex formation function	biocomplexes regulate the functioning of internal membranes and cell organelles

The role of proteins in the human body

construction function. The nutrients that come from food are not identical to the proteins, fats and carbohydrates in our body.

So, proteins in the stomach under the action of the enzyme pepsin are lysed to amino acids. They, in turn, are transported to the small intestine, where they are converted into new, “own” amino acids, which then enter the lymph and cells.

Thus, in the body, proteins are again built from external amino acids, specific to a particular organism.

structural function. A special case of building is the structural role of protein substances. The cell wall and the membrane of any of its organelles is a protein with fatty inclusions. Microtubules and filaments involved in the divergence of nuclei to opposite poles of the cell during cell division are of a protein nature.

synthesis function. Millions of reactions are going on continuously in any cell. Almost all of them come with the participation of proteins (enzymes). Biological catalysts - enzymes - many times accelerate the course of bioreactions.

All enzymes are proteins. Each of them is responsible for the flow of strictly one transformation or several reactions of the same type. For example, fats are decomposed into simpler components - glycerol and higher fatty acids - by a special enzyme, which is not affected by carbohydrates or proteins. In turn, the biocatalyst responsible for the breakdown of sugars does not affect fats or proteins.

regulatory function. All physiologically active substances most often act as proteins. Thus, the pancreatic hormone insulin (represents a sequence of 51 amino acids) ensures the storage of glucose molecules in the liver in the form of glycogen polysaccharide, which, during carbohydrate starvation, will again be broken down to glucose molecules.

Hormones have the most important function, subordinating the activity of enzymes.

protective function. The body responds to the introduction of viruses, bacteria and other alien creatures and substances by producing protective proteins - antibodies. They block foreign agents, suppressing their physiological activity.

For each toxin, the body forms its own antibodies.

Among millions of foreign proteins, they recognize the right one and only interact with it. This ability underlies immunity.

• The protective function is also manifested in the ability of blood to coagulate. Fibrinogen is involved.
• Interferon is produced in response to the attack of viruses.
• Saliva lysozyme protects against microorganisms.
• Immunoglobulins neutralize harmful effects.

Energy function. It is a mistake to think that carbohydrates are the most high-calorie substances. They just get absorbed faster. In terms of energy value, proteins are in no way inferior to them.

When burning 1 g of protein, the same amount of energy is released as when burning carbohydrates, i.e. 4.1 kcal (16.1 kJ).

With a lack of carbohydrates and fats, protein molecules begin to oxidize, releasing the energy of chemical bonds contained in them. The released energy covers the costs of the implementation of life processes.

Signal function. The high specificity of antibody binding to a specific antigen (foreign substance) is achieved due to the fact that on the surface of both the antigen and the antibody there are special proteins that interact only with each other.

According to the same principle, the hormone molecule “recognizes” the target cell, exercising endocrine control.

receptor function. A special case of the previous function is the receptor role of proteins. In order for the cells of the body to “recognize” each other or identify the toxin, identification molecules must be on their surface - receptors, which are proteins. Many vital processes are based on the recognition mechanism.

transport function. Proteins with small, mobile, highly soluble molecules are suitable for transporting substances. Hemoglobin consists of a non-protein part - heme - and globin protein.

• Hemoglobin delivers oxygen to cells and tissues.
• Higher fatty acids, vitamins, drugs are also carried by proteins.
• Blood plasma albumins carry fatty elements.

motor function. Proteins with filamentous molecules are an integral component of muscles. They are able to lengthen, shorten and stretch and provide motor activity of cells. So, tropomyosin, troponin, actin and myosin carry out muscle contraction. Proteins that ensure the divergence of chromosomes also play a motor role.

Function of formation of biocomplexes. The human body is such a complex system that for the implementation of any act, several stages of reactions must occur. The control of such multistage processes is monitored not by one protein, but by whole cascade, where each component does its job and add-on in case something went wrong.

There is no cell or organ in which protein components would not be present. Without these molecules, it is impossible to carry out physiological processes.

I. Table 2. Classification of proteins according to their structure.

Protein class	Characteristic	Function
fibrillar	The secondary structure is most important (the tertiary structure is almost not expressed) Insoluble in water Differ in high mechanical strength Long parallel polypeptide chains, fastened to each other by cross-links, form long fibers or layered structures	Perform structural functions. This group includes, for example, collagen (tendons, bones, connective tissue), myosin (muscles), fibroin (silk, cobweb), keratin (hair, horns, nails, feathers).
Globular	Tertiary structure is most important Polypeptide chains are coiled into compact globules Soluble	They act as enzymes, antibodies, and in some cases hormones (such as insulin) and a number of other important functions
Intermediate	Fibrillar in nature, but soluble	An example is fibrinogen, which is converted to insoluble fibrin during blood clotting.

II. Classification of proteins according to their composition.

Simple Complex

Composed only of amino acids Consists of globular proteins and non-protein

material. The non-white part is called

prosthetic group.

Table 3. Complex proteins.

Name	Prosthetic group	Example
Phosphoproteins	Phosphoric acid	Milk casein Egg yolk vitellin
Glycoproteins	Carbohydrate	Membrane components Mucin (component of saliva)
Nucleoproteins	Nucleic acid	Components of viruses Chromosomes Ribosomes
Chromoproteins	Pigment	Hemoglobin - heme (iron-containing pigment) Phytochrome (pigment of potent origin) Cytochrome (respiratory pigment)
Lipoproteins	Lipid	Membrane components Blood lipoproteins - the transport form of lipids
Metalloproteins	Metal	Nitrareductase is an enzyme that catalyzes the conversion of sodium to nitrite in plants.

III. Table 4. Classification of proteins by function.

Protein class	Examples	Localization/function
Structural proteins	Collagen Keratin Elastin	Component of connective tissue, bones, tendons, cartilage Skin, feathers, nails, hair, horns Ligaments
Enzymes	Trypsin Ribulose bisphosphate carboxylase	Catalyzes the hydrolysis of proteins Catalyzes (addition of CO 2) during photosynthesis
Hormones	Insulin Glucagon ACTH	Regulate glucose metabolism Stimulates the growth and activity of the adrenal cortex
Respiratory pigments	Hemoglobin Myoglobin	Carries O 2 in the blood of vertebrates Serves to store O 2 in muscles
Transport proteins	Albumen	Serves for the transport of fatty acids and lipids in the blood
Protective proteins	Antibodies Fibrinogen Thrombin	Form complexes with foreign proteins Fibrin precursor during blood clotting Involved in the process of blood clotting
Contractile proteins	myosin Actin	Movable muscle filaments Fixed muscle filaments
Spare proteins	Egg Albumin Casein	egg white milk protein
toxins	snake poison	Enzymes

Enzymes(enzymes) - specific proteins that are present in all living organisms and play the role of biological catalysts.

Enzymes speed up reactions without changing its overall result.

Enzymes are highly specific: each enzyme catalyzes a specific type of chemical reaction in cells. This ensures fine regulation of all vital processes (respiration, digestion, photosynthesis, etc.)

Example: the enzyme urease catalyzes the breakdown of urea only, without exerting catalytic pressure on structurally related compounds.

The activity of enzymes is limited by a rather narrow temperature range (35-45°C), beyond which the activity falls and disappears. Enzymes are active at physiological Ph values, i.e. in a slightly alkaline environment.

In terms of spatial organization, enzymes consist of several domains and usually have a quaternary structure.

Enzymes can also contain non-protein components. The protein part is called apoenzyme , and non-protein - cofactor (if it is a simple inorganic substance, for example Zn 2+ , Mg 2+) or coenzyme (coenzyme) ) (if we are talking about organic compounds).

The precursors of many coenzymes are vitamins.

Example: pantathenic acid is a precursor of coenzyme A, which plays an important role in metabolism.

In enzyme molecules there is a so-called active center . It consists of two sections - sorption and catalytic . The former is responsible for the binding of enzymes to substrate molecules, while the latter is responsible for the actual act of catalysis.

The name of the enzymes contains the name of the substrate, which is affected by this enzyme, and the ending "-ase".

Cellulose - catalyzes the hydrolysis of cellulose to monosaccharides.

ü Protease - hydrolyzes proteins to amino acids.

According to this principle, all enzymes are divided into 6 classes.

Oxidoreductase catalyze redox reactions, carrying out the transfer of H and O atoms and electrons from one substance to another, while oxidizing the first and reducing the second. This group of enzymes is involved in all processes of biological oxidation.

Example: in the breath

AN + B ↔A + BH (oxidative)

A + O ↔ AO (reducing)

Transferases catalyze the transfer of a group of atoms (methyl, acyl, phosphate and amino groups) from one substance to another.

Example: under the pressure of phosphotransferases, phosphoric acid residues are transferred from ATP to glucose and fructose: ATP + glucose ↔ glucose - 6 - phosphate + ADP.

Hydrolases accelerate reactions split complex organic compounds into simpler ones by attaching water molecules at the site of breaking chemical bonds. Such splitting is called hydrolysis .

These include amylase (hydrolyzes starch), lipase (breaks down fats), etc.:

AB + H 2 O↔AOH + VN

Liase catalyze non-hydrolytic additions to the substrate and the elimination of a group of atoms from it. In this case, there may be a break in the connection C - C, C - N, C - O, C - S.

Example: removal of a carboxyl group by a decarboxylase

CH 3 - C - C ↔ CO 2 + CH 3 - C

Isomerases carry out intramolecular rearrangements, i.e. catalyze the transformation of one isomer into another:

glucose - 6 - phosphate ↔ glucose - 1 - phosphate

Lipases( synthetases) catalyze the reactions of joining two molecules with the formation of new bonds C - O, C - S, P - N, C - C, using the energy of ATP.

Lipases are a group of enzymes that catalyze the addition of amino acid residues to tRNA. These synthetases play an important role in the process of protein synthesis.

Example: the enzyme valine - t-RNA - synthetase under its action forms a valine-t-RNA complex:

ATP + valine + tRNA ↔ ADP + H 3 PO 4 + valine-tRNA

The lesson was developed by the teacher of biology and chemistry Grabina N.V. The goals, methods and type of lesson are clearly indicated, equipment is listed. The structure of the lesson is strictly maintained. Checking the acquired knowledge is carried out by different forms of survey. When studying new material, the teacher uses interesting techniques, motivates and involves students in the work. The result of such work is the "Protein Functions" table. This lesson uses innovative technologies: problematic, intellectual, group, information and communication. The outline of this lesson can be used by middle school teachers and VET teachers.

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TOPIC OF THE LESSON: Squirrels. Composition, structure, structure and functions of proteins.

LESSON OBJECTIVES: 1. Educational: to update students' knowledge of proteins from the school biology course; expand knowledge about the structure and functions of proteins;

2. Developing: develop the ability to systematize your knowledge, use additional literature; be able to use methods of comparison, generalization, draw conclusions.

3. Educational: follow the rules of working in a team.

EQUIPMENT: computer, presentation "Levels of protein organization"; tables "Human Skeleton and Muscles"; "Infusoria-shoe"; reference schemes "Amino acids"; "The composition of proteins"; hemoglobin protein model; reference notes "Protein Functions"; dynamic model of protein structure; drawings "Mulberry silkworm"; "Erythrocytes"; wool and leather collection; tubes, N 2 O 2 ; pieces of boiled and raw meat and potatoes; packages with grains of wheat, corn; eggs, milk; bean seeds.

Lesson type : combined.

Teaching methods and techniques: problematic, verbal-visual, information and communication, problem solving, speeches.

Conduct form: lesson-seminar.

DURING THE CLASSES.

I. Organizational moment.

II. Updating of basic knowledge.

1. Individual survey (at the blackboard) on the topic "Inorganic substances of the cell":

The chemical composition of the cell;

Water, its importance for the body;

Mineral salts, value of cations and anions;

2. Work on cards (macroelements, microelements, ultramicroelements of the cell).

3. a) Frontal survey:

What does cytology study?

Name the main stages in the development of cytology.

Who was the first to discover cells - cells on a cut of an elderberry cork?

Who discovered unicellular organisms?

Name the scientists who were the first to prove that all plants and animals are made up of cells.

What is a cell in the light of modern cell theory?

B) Entertaining tasks:

Plants have been found to use, on average, less than 1% of the water they absorb. Where is the rest spent?

Answer: most of the water is spent on transpiration - the evaporation of water from the surface of the plant.

How do spiders breathe in water?

Answer: The silver spider “builds” an air bell, repeating complex operations several times to deliver air bubbles.

III. Motivation of educational activity. Learning new material.

1. Introductory speech of the teacher:

In biology classes at school, most of you studied the topic "Squirrels".

What do you remember about proteins from the school biology course? (Reference notes)

Proteins are high molecular weight organic compounds that are part of living organisms. “Wherever we meet life, we find that it is associated with some protein body, and wherever we meet any protein body that is not in the process of decomposition, we, without exception, meet the phenomena of life.”

"Life is a way of existence of protein bodies."

The beginning of the chemical study of proteins was laid by the Italian Beccari (1728), when he isolated gluten, a new class of substances, from wheat. A huge contribution to the study of the structure of protein molecules was made by the German scientist, Nobel Prize winner Emil Fischer (1852-1919). For 10 years he was engaged in the synthesis of amino acids and came to the conclusion that they are interconnected by a CO-NH peptide bond (1907). Fisher's theory is the main one in protein chemistry. Proteins are polymers whose monomers are amino acids. There are 20 amino acids (tables on tables). Distinguish between nonessential and irreplaceable, or "magic" amino acids. The molecular weight of proteins ranges from 6500 (insulin) to 32,000,000 (influenza virus protein). If a protein molecule consists of 20 different amino acids, then there are 2432902008178640000 isomers!!! Despite the diversity in structure, the composition of protein molecules is limited by the number of elements: C - 50-55%; O - 21-24%; N - 15-18%; H - 6-7% S - 0.3-2.5% Some proteins contain P (milk), Fe (blood), Mg (chlorophyll), Zn, Cu, Se. There are more proteins in the body of animals than in the body of plants.

2. Explanation of the teacher with elements of conversation and comments from students.

A) Classification of proteins:

I. By chemical composition:

/ \

Proteins

(during hydrolysis, they form (during hydrolysis, amino acids and

Only amino acids) other components of non-protein nature-

Carbohydrates, nucleic acids, H3PO4)

Glycoproteins;

Nucleoproteins;

Lipoproteins

II. According to the shape of the molecule:

/ \

Fibrillar Globular

(long, filamentous; (dense compact structure of spherical

structural and protective functions) forms; enzymatic, transport functions;

Antibodies.)

B) The structure of proteins.

Dynamic modeling of levels of organization of a protein molecule. (student)

Primary (sequence of amino acids in the polypeptide chain - peptide bond);

Secondary (spatial configuration in the form of a spiral, or accordion - hydrogen bond);

Tertiary (spatial configuration in the form of a globule, or a ball - disulfide, covalent, ionic, hydrogen bond);

Quaternary (a set of several tertiary structures). An example is a hemoglobin molecule (model demonstration).

3. Teacher's explanation.

Protein properties:

1) The chemical properties of proteins determine the various functional groups that make up their molecules:

COOH (acid properties) and NH 2 (basic properties)

In general, amino acids exhibit amphoteric properties.

2) Denaturation - a violation of the protein structure, a change in physical, chemical

CIR and biological properties (with a change in t °, irradiation, a sharp change in the pH of the medium)

Denaturation

/ \

Reversible Irreversible

(if the primary structure is not destroyed) (all structures are destroyed)

Renaturation - the process of restoring the natural structure of the protein.

4. Performance of students with messages and demonstration of posters, drawings and natural objects (functions of proteins):

Construction function (demonstration: animal skeleton, deer antlers, drawing of a spider and cobweb, silkworm);

Regulatory (demonstration: poster "Human Digestive System", pancreas - drawing);

Transport (hemoglobin protein model, erythrocyte pattern);

Catalytic (demonstration of experience with H 2 O 2 and natural products)

Protective (poster "Human circulatory system", drawing of leukocytes, platelets);

Contractile (poster "Human Muscles", "Protozoa: ciliates - shoe");

Energy (comparative table "Energy value of organic substances");

Storage (demonstration: packaging of milk, grains of wheat, rye, corn, chicken egg).

As students speak, the table in notebooks is filled in.

FUNCTIONS OF PROTEINS

Function name	Examples of proteins		Function characteristic
1. Construction (structural)	Keratin	Hairline, bones, nails	Participation in the formation of all cell membranes and cell organelles.
	Collagen Fibroin Ossein	Connective tissue, insect glands, bones	The formation of threads of natural silk.
2. Regulatory	Insulin	Pancreas	Regulates the intake and level of glucose in the blood. The function of hormones that affect the activity of enzymes.
	Histones A growth hormone	In blood
3. Transport	Hemoglobin	Red blood cells	Carries O 2, nutrients and CO 2.
	Albumins	Blood	Transport of fatty acids.
4. catalytic	B-enzymes Catalase Ribonuclease trypsin	In all cells and tissues of animals and plants	They speed up chemical reactions, promote the breakdown of nutrients and harmful compounds.
5. Protective	blood antibodies fibrinogen Thrombin Interferon	circulatory system (leukocytes)	immune defense of organisms. Blood clotting. Suppresses the development of viruses.
6. Contractile	actin Myosin fibril	Muscle fibres. Structure of cilia and flagella of protozoa	Muscle contraction. Protozoan movement. All kinds of movements.
7. Energy	All squirrels	Cells of all organisms	Energy source for cells (1g of protein - 17.6 kJ of energy)
8. Spare (nutritional)	Casein	Milk	Supply of nutrients.
	Albumen	Eggs
	Gluten	Wheat
	Zein	Corn

IV. REINFORCEMENT OF LEARNED

1. Teacher's conclusions

The functions performed determine the biological significance of proteins.

The main quality of dietary protein is the ability to supply the body with amino acids.

Organization of proper nutrition! (Not only quantity, but also quality).

Most Valuableanimal proteins- milk, cheese (2.2%) and dairy products: eggs, fish (18%), meat (20%).

Plant Protein Sources- cereals (flour, cereals, pasta) and legumes (beans, peas).

Vegetables are poor in protein, but they contribute to better digestibility of proteins.

2. Student performance:

Obtaining artificial protein food and feed;

Chemical methods (from hydrocarbons - oil);

microbiological methods.

3. Frontal final conversation with students.

What did you study? (Game "Chain")

Everyone expresses 3 main concepts that are most remembered.

V. HOMEWORK.

Learn the summary, finish the work on the table.

Recall from the school biology course the structure and function of carbohydrates and lipids.

Continuation. See No. 11, 12, 13, 14/2005

Biology lessons in science classes

Advanced Planning, Grade 10

III. Consolidation of knowledge

Filling in the table "Levels of protein organization".

Table 5. Levels of protein organization

Organization level	signs	Links involved in the formation of the structure
Primary	The linear sequence of amino acids in a polypeptide chain	Covalent (peptide) bonds between the residue of the carboxyl group of one amino acid and the residue of the amino group of another amino acid
Secondary	Spiral, -structure or spirals with parameters other than -spirals	Hydrogen bonds between the residues of the carboxyl group of one amino acid and the residue of the amino group of the other, remote from the first by four amino acid residues; in the -structure, hydrogen bonds between the residues of the carboxyl and amino groups of one chain and the residues of the same groups of the other chain; in spirals - similar to -spirals, but the distance between the turns is different
Tertiary	A globule formed as a result of compact stacking - a spiral; -structures laid in parallel layers; supercoil - several spirals twisted together	Ionic, disulfide bridges, hydrophobic, hydrogen
Quaternary	An aggregate of several globules. It is peculiar only to proteins with a particularly complex structure	Mainly forces of intermolecular attraction, to a lesser extent - hydrogen, ionic and covalent

IV. Homework

To study a textbook paragraph (proteins, their content in living matter, the structure and properties of amino acids, the formation of peptides, levels of protein organization, protein classification).

Lesson 10-11. Biological functions of proteins

Equipment: tables on general biology, diagrams and drawings illustrating the structure of proteins, a scheme for classifying proteins.

I. Knowledge Test

Card work

Card 1. A young biochemist, determining the nitrogen content in a pure protein preparation, obtained a value of 39.9%. How can you comment on this result?

Card 2. The hemoglobin protein occurs in humans in two variants:

hemoglobin in the blood of a healthy person (... val-ley-ley-tre-pro-val-glu-liz ...);

hemoglobin in the blood of a patient with sickle cell anemia (... val-ley-ley-tre-pro-glu-glu-lys...). What caused the disease?

Card 3. How to determine the number of possible amino acids in a protein by molecular weight? What determines the possible error of this estimate?

Card 4. How many variants of polypeptide chains can exist, including 20 amino acids and consisting of 50 amino acid residues? Out of 200 leftovers?

Card 5. Fill in the gaps in the text: “As a result of the interaction of various ... and the formation of ... bonds, a spiralized protein molecule forms ... a structure, which, in turn, depends on ... the structure of the protein, that is, on ... amino acids in a polypeptide molecule. The subunits of some proteins form... a structure. An example of such a protein is ... ".

Card 6. Ions of heavy metals (mercury, lead) and arsenic easily bind to sulfide groups of proteins. Knowing the properties of the sulfides of these metals, explain what happens to the protein when combined with these metals. Why are heavy metals poisonous to the body?

1. Proteins, their content in living matter, molecular weight.

2. Proteins are non-periodic polymers. The structure and properties of amino acids. The formation of peptides.

3. Primary and secondary structures of a protein molecule.

4. Tertiary and quaternary protein structures.

5. Classification of proteins.

II. Learning new material

1. Denaturation and other properties of proteins

Proteins are extremely diverse in their physical and chemical properties. What is the reason for this? ( Conversation.) Let us give examples of the diversity of properties of proteins.

1. There are proteins soluble (for example, fibrinogen) and insoluble (for example, fibrin) in water.

2. There are proteins that are very stable (for example, keratin) and unstable (for example, the catalase enzyme with an easily changing structure).

3. Proteins have a variety of molecular shapes - from threads (myosin - muscle fiber protein) to balls (hemoglobin), etc.

But always the structure and properties of the protein correspond to the function it performs.

The most important property of all living systems, irritability, is based on the ability of proteins to reversibly change their structure in response to the action of physical and chemical factors. Since the secondary, tertiary, and quaternary structures of a protein are generally created by weaker bonds than the primary, they are less stable. For example, when heated, they are easily destroyed. At the same time, although the primary structure of the protein is preserved intact, it cannot perform its biological functions and becomes inactive. The process of destruction of the natural conformation of a protein, accompanied by a loss of activity, is called denaturation. Breakage of part of the weak bonds, changes in conformation and properties also occur under the influence of physiological factors (for example, under the action of hormones). Thus, the properties of proteins - enzymes, receptors, transporters - are regulated.

These structural changes are usually easily reversible. The reverse denaturation process is called renaturation. This property of proteins is widely used in the medical and food industries for the preparation of certain medical preparations, such as antibiotics, vaccines, sera, enzymes; to obtain food concentrates that retain their nutritional properties for a long time in dried form.

If the restoration of the spatial configuration of the protein is impossible, then denaturation is considered irreversible. This usually happens when a large number of bonds are broken, such as when boiling eggs.

Thus, proteins have a complex structure, various shapes and composition. This makes their properties diverse. And this, in turn, allows proteins to perform numerous biological functions.

2. Biological functions of proteins

Proteins perform a number of important functions in the cell and the body, the main of which are the following.

1. Structural (construction). Proteins are part of all cell membranes and cell organelles, as well as extracellular structures. An example of a protein that performs a structural function is keratin. Hair, wool, horns, hooves, and the upper dead layer of the skin are composed of this protein. Protein pads are located in the deeper layers of the skin collagen and elastin. It is these proteins that provide strength and elasticity to the skin. They are also contained in the ligaments that connect muscles to joints and joints to each other.

2. Enzymatic. Proteins are biological catalysts. For example, pepsin, trypsin, etc. (we will consider the properties of enzyme proteins in detail in the next lessons).

3. Motor. Special contractile proteins are involved in all types of cell and organism movement: the formation of pseudopodia, the flickering of cilia and the beating of flagella in protozoa, muscle contraction in multicellular animals, the movement of leaves in plants, etc. Thus, muscle contraction is provided by muscle proteins actin and myosin, they also make amoeba crawling possible.

4. Transport. In the blood, in the outer cell membranes, in the cytoplasm and nuclei of cells, there are various transport proteins. There are transporter proteins in the blood that recognize and bind certain hormones and carry them to target cells. In the outer cell membranes there are transporter proteins that provide active and strictly selective transport of sugars, amino acids, and various ions into and out of the cell. Other transport proteins are also known, for example hemoglobin and hemocyanin that carry oxygen, and myoglobin holding oxygen in the muscles.

5. Protective. In response to the penetration of foreign proteins or microorganisms with antigenic properties into the body, blood lymphocytes form special proteins - antibodies that can bind and neutralize them. Saliva and tears contain protein lysozyme An enzyme that breaks down bacterial cell walls. If a microbe enters the mucous membrane of the eye or oral cavity, its shell is destroyed under the action of lysozyme, and then protective cells easily cope with it. Fibrin and thrombin help stop bleeding.

6. Energy (nutritional). Proteins can be broken down, oxidized and given the energy needed for life. True, this is not very profitable: the energy value of proteins is low compared to fats and amounts to 17.6 kJ (4.1 kcal) of energy per 1 g of protein. Typically, proteins are consumed for energy needs in extreme cases, when the reserves of fats and carbohydrates are exhausted.

7. Regulatory. Many (though by no means all) hormones are proteins - for example, all hormones of the pituitary, hypothalamus, pancreas ( insulin, glucagon), etc. Hormones act on the cell by binding to specific receptors. Each receptor recognizes only one hormone. All hormone receptors are proteins. Another example is proteins that regulate the formation and growth of individual organs and tissues during the development of an organism from a zygote. Phytochrome plants is a complex photosensitive protein that regulates the photoperiodic response in plants.

8. Signal (receptor). Molecules of proteins are embedded in the surface membrane of the cell, capable of changing their tertiary structure in response to the action of environmental factors. This is how signals from the external environment are received and commands are transmitted to the cell.

9. Spare. Thanks to proteins, certain substances can be stored in the body. egg albumin serves as the water-storage protein in the egg white, the milk casein is the source of energy, and the protein ferritin retains iron in the egg yolk, spleen and liver.

10. Toxic. Some proteins are toxins: cobra venom contains neurotoxin.

III. Consolidation of knowledge

Generalizing conversation in the course of learning new material.

IV. Homework

Study the paragraph of the textbook (properties of proteins and their biological functions).

Lesson 12-13. Enzymes, their chemical composition and structure. The biological role of enzymes

Equipment: tables on general biology, diagrams and drawings illustrating the structure and mechanism of action of enzymes, a classification scheme for enzymes, equipment for laboratory work.

I. Knowledge Test

Card work

Card 1. It has been established that with sufficient caloric content of food, but in the absence of protein in it, pathological phenomena are observed in animals: growth stops, blood composition changes, etc. What is it connected with?

Card 2. Why are proteins called "carriers and organizers of life"?

Card 3. What structural features of a protein molecule provide it with the performance of many functions, for example, transport, protective, energy?

Card 4. Fill in the gaps in the text: “Defensive proteins are called .... They bind to... that enter the body and are called... . Among thousands of different proteins... only one is recognized... and reacted with. Such a mechanism of resistance to pathogens is called ... ".

Card 5. What are the similar functions of proteins, carbohydrates and lipids in living organisms?

Oral knowledge test on questions

1. Denaturation and other properties of proteins. Connection of the structure, properties and functions of proteins.

2. Biological functions of proteins ( three students).

II. Learning new material

1. Enzymes and their importance in life processes

From the course of chemistry, you know what a catalyst is. This is a substance that speeds up the reaction, remaining unchanged at the end of the reaction (not consumed). Biological catalysts are called enzymes(from lat. fermentum- fermentation, sourdough), or enzymes.

Almost all enzymes are proteins (but not all proteins are enzymes!). In recent years, it has become known that some RNA molecules also have the properties of enzymes.

For the first time, a highly purified crystalline enzyme was isolated in 1926 by the American biochemist J. Sumner. This enzyme was urease, which catalyzes the breakdown of urea. To date, more than 2 thousand enzymes are known, and their number continues to grow. Many of them are isolated from living cells and obtained in pure form.

There are thousands of reactions going on in the cell all the time. If you mix organic and inorganic substances in a test tube in exactly the same proportions as in a living cell, but without enzymes, then almost no reactions will occur at a noticeable rate. It is thanks to enzymes that genetic information is realized and the entire metabolism is carried out.

The name of most enzymes is characterized by the suffix -ase, which is most often added to the name of the substrate - the substance with which the enzyme interacts.

2. The structure of enzymes

Compared to the molecular weight of the substrate, enzymes have a much larger mass. This discrepancy suggests that not the entire enzyme molecule is involved in catalysis. To understand this issue, it is necessary to get acquainted with the structure of enzymes.

By structure, enzymes can be simple and complex proteins. In the second case, in the composition of the enzyme, in addition to the protein part ( apoenzyme) there is an additional group of non-protein nature - an activator ( cofactor, or coenzyme), resulting in the formation of an active holoenzyme. Enzyme activators are:

1) inorganic ions (for example, to activate the amylase enzyme in saliva, chloride ions (Cl–) are needed);

2) prosthetic groups (FAD, biotin) strongly associated with the substrate;

3) coenzymes (NAD, NADP, coenzyme A), loosely bound to the substrate.

The protein part and the non-protein component separately are devoid of enzymatic activity, but, when combined together, they acquire the characteristic properties of an enzyme.

The protein part of enzymes contains active centers unique in their structure, which are a combination of certain amino acid residues strictly oriented with respect to each other (at present, the structure of the active centers of a number of enzymes has been deciphered). The active center interacts with the substrate molecule to form an "enzyme-substrate complex". The "enzyme-substrate complex" then breaks down into an enzyme and a reaction product or products.

According to the hypothesis put forward in 1890 by E. Fisher, the substrate approaches the enzyme as key to the castle, i.e. the spatial configurations of the active site of the enzyme and the substrate exactly match ( complementary) each other. The substrate is compared to a "key" that fits the "lock" - the enzyme. Thus, the active center of lysozyme (saliva enzyme) has the form of a gap and in shape exactly corresponds to a fragment of a complex carbohydrate molecule of a bacterial bacillus, which is cleaved under the action of this enzyme.

In 1959, D. Koshland put forward a hypothesis according to which the spatial correspondence between the structure of the substrate and the active center of the enzyme is created only at the moment of their interaction with each other. This hypothesis has been called the "hands and gloves" hypothesis(hypothesis of induced interaction). This process of "dynamic recognition" is by far the most widely accepted hypothesis.

3. Differences between enzymes and non-biological catalysts

Enzymes are different from non-biological catalysts in many ways.

1. Enzymes are much more efficient (10 4 -10 9 times). So, a single molecule of the catalase enzyme can break down 10,000 molecules of hydrogen peroxide, which is toxic to a cell, in one second:

2H 2 O 2 -–> 2H 2 O + O 2,

which occurs when various compounds are oxidized in the body. Or another example confirming the high efficiency of the action of enzymes: at room temperature, one urease molecule is capable of splitting up to 30 thousand urea molecules in one second:

H 2 N–CO–NH 2 + H 2 O -–> CO 2 + 2NH 3.

Without a catalyst, this would take about 3 million years.

2. High specificity of enzyme action. Most enzymes act on only one or a very small number of "their" natural compounds (substrates). The specificity of enzymes reflects the formula "one enzyme - one substrate". Due to this, in living organisms, many reactions are catalyzed independently.

3. Enzymes are available for fine and precise regulation. The activity of an enzyme can increase or decrease with a slight change in the conditions under which it "works".

4. Non-biological catalysts generally work well only at high temperatures. Enzymes, being present in cells in small quantities, work at normal temperature and pressure (although the scope of enzyme action is limited, since high temperature causes denaturation). Since most enzymes are proteins, their activity is highest under physiologically normal conditions: t=35–45 °C; slightly alkaline environment (although each enzyme has its own optimal pH value).

5. Enzymes form complexes - the so-called biological conveyors. The process of splitting or synthesis of any substance in the cell, as a rule, is divided into a number of chemical operations. Each operation is performed by a separate enzyme. A group of such enzymes constitutes a kind of biochemical pipeline.

6. Enzymes are able to be regulated, i.e. “turn on” and “turn off” (although this does not apply to all enzymes, for example, saliva amylase and a number of other digestive enzymes are not regulated). In the majority of apoenzyme molecules there are sections that also recognize the final product, which “descends” from the polyenzyme conveyor. If there is too much of such a product, then the activity of the initial enzyme itself is inhibited by it, and vice versa, if there is not enough product, then the enzyme is activated. This regulates many biochemical processes.

Thus, enzymes have a number of advantages over non-biological catalysts.

4. Mechanism of action of enzymes

Enzymes act in living organisms according to the same laws as any catalysts. Enzymatic catalysis is based on a decrease in the energy barrier (the so-called activation energy) due to the formation of intermediate complexes of the enzyme with the substrate. In the absence of, for example, amylase, the reaction between starch and water does not proceed because the molecules do not have sufficient energy for this purpose. The enzyme speeds up the chemical process, because. in its presence, less energy is required to "start" this reaction. Let us consider the mechanism of action of enzymes in more detail.

1. Catalyzing the reaction, the enzyme closely brings together the molecules of "its" substrates, so that those parts of the molecules that are to react are nearby.

2. The substrate, having joined the enzyme, changes somewhat. The enzyme can attract electrons, as a result of which a voltage will appear in some bonds of the substrate molecule. This, in turn, increases the reactivity of the molecule, since the bonds between the atoms are weakened, and they are more easily released (it is assumed that this is how the enzyme speeds up the reaction).

3. The enzyme “rips off” an atom (or atoms) from each of the substrates, after which the substrates are combined.

4. The separated atoms combine with each other and leave the enzyme. The enzyme is now able to attach new substrate molecules.

Most often, enzymes are confined to certain cellular structures. They retain their properties outside the body. Enzymes are successfully used in the baking, brewing, winemaking, leather, and chemical industries.

5. Classification of enzymes

Students work with the text of the textbook and fill in the table "The most important groups of enzymes" with subsequent verification.

Table 6. The most important groups of enzymes

Class number and name	Catalyzed reactions
1. Oxidoreductases 2. Transferases 3. Hydrolases 4. Liases 5. Isomerases 6. Ligases (synthetases)	Redox reactions: the transfer of hydrogen or oxygen atoms or electrons from one substance to another Transfer of functional groups from one substance to another Hydrolysis: the reactions of splitting complex organic substances into simpler ones by adding water Non-hydrolytic addition or elimination of functional groups Isomerization, i.e. conversion of isomers into each other Synthesis reactions using the energy of ATP	Catalase decomposes hydrogen peroxide into water and molecular oxygen; Cytochromes transfer and attach electrons to oxygen atoms during respiration and to protons during the reactions of the light phase of photosynthesis Phosphotransferases transfer phosphoric acid residues from ATP to glucose or fructose. Amylase hydrolyzes starch to maltose; trypsin hydrolyzes proteins and peptides to amino acids Cleavage of carboxyl groups by decarboxylases Interconversions of glucose and fructose in plants under the action of glucose phosphate isomerase Carboxylase catalyzes the addition of carbon dioxide to organic acids.

III. Consolidation of knowledge

Laboratory work No. 1. "Study of the catalytic activity of the catalase enzyme in living tissues"

Equipment: tripods, test tubes, flasks with fresh 3% hydrogen peroxide solution, plant and animal tissues, jars of water and elodea, microscopes, glass slides and coverslips, tweezers and pipettes.

Progress

1. Pour 2 ml of hydrogen peroxide into test tubes with raw meat, boiled meat, raw and boiled potatoes. Explain the phenomena you observe during the action of peroxide on living and dead tissues.

2. Place an elodea leaf in a drop of water on a glass slide and examine under a microscope at low magnification the place where the leaf is torn off the stem.

3. Apply two drops of hydrogen peroxide to the elodea leaf, cover with a cover slip and examine under a microscope the place where the leaf is torn off the stem. Explain the rapid release of gas bubbles from damaged Elodea leaf cells.

4. Conclusions.

How is enzyme activity manifested in living and dead tissues? Why?

Does the activity of the enzyme differ in the living tissues of plants and animals?

How would you suggest measuring the decomposition rate of hydrogen peroxide?

Do you think that all living organisms contain the enzyme catalase, which decomposes hydrogen peroxide? Justify the answer.

IV. Homework

Study the paragraph of the textbook (enzymes, their meaning, structure, mechanism of action and classification).

Lesson 14-15. Nucleic acids are non-periodic polymers. The structure of a nucleotide. The formation of polynucleotides. Formation of a double-stranded DNA molecule. The principle of complementarity

Equipment: general biology tables, diagrams and drawings illustrating the structure and mechanism of enzyme action, enzyme classification scheme, nucleotide structure diagram, DNA structure model.

I. Knowledge Test

Card work

Card 1. It is known that the rate of chemical reactions with a decrease in temperature by 10 ° C decreases only 2–3 times. For greater stability of the analyzed samples, biochemists store them at a low temperature. Nevertheless, if a freezing person's body temperature drops by at least 10 ° C, then this leads to serious, often irreversible consequences. Is there a contradiction here?

Card 2. From the notebooks of Kifa Mokievich: “Protease is an enzyme that cleaves peptide bonds in proteins. Amylase is an enzyme that cleaves glycosidic bonds in carbohydrates. It is known that all enzymes have extremely high specificity and fit the substrate like a key to a lock. Since the substrates of the enzymes are the same, then the enzymes themselves are the same. It follows that it is enough for biochemists to study one amylase (say, from human saliva) and one protease (say, from washing powder) - they are identical! How could you object to Kifa Mokievich?

Card 3. An enzyme has been isolated from rat tissue. Its solution at +4 °C retains catalytic activity for several weeks. After it was placed in a thermostat at +40°C for 2 hours, it lost 50% of its activity. Is it true that after another 2 hours it would become completely inactive? But in the body of a rat, it is by no means +4 ° С, but just +40 ° С. So does she need such an unstable enzyme?

Card 4. Try to make a list of enzymes necessary for the existence of any cell. If you do not know the name of an enzyme, it is enough to indicate the reaction it catalyzes.

Card 5. The experimenter, studying the rate of protein cleavage by the protease, found that over time it first increased several times, and then fell - until the complete loss of enzyme activity. How can this pattern be explained? What proteases do you think have this property?

Card 6. Why can enzyme activity be affected by pH?

Card 7. In what ways can a cell control the rates of chemical processes occurring in it? And in what ways can the human body regulate the speed of chemical processes?

Card 8. How do you understand the "catalytic (enzymatic) pipeline in the cell"? What is the advantage of the conveyor arrangement of enzyme molecules on the membrane in comparison with their free, random arrangement in the cytoplasm?

Oral knowledge test on questions

1. Enzymes and their importance in life processes.

2. The structure of enzymes and the reason for their high specificity.

3. Differences between enzymes and non-biological catalysts.

4. The mechanism of action of enzymes.

5. Classification of enzymes.

II. Learning new material

1. Nucleic acids, their content in the cell, molecular size and molecular weight

Nucleic acids are natural high-molecular organic compounds, polynucleotides that provide storage and transmission of hereditary (genetic) information in living organisms.

These organic compounds were discovered in 1869 by the Swiss physician I.F. Misher in cells rich in nuclear material (leukocytes, salmon spermatozoa). Nucleic acids are an integral part of cell nuclei, which is why they got their name (from lat. nucleus- nucleus). In addition to the nucleus, nucleic acids are also found in the cytoplasm, centrioles, mitochondria, and chloroplasts.

There are two types of nucleic acids in nature: deoxyribonucleic (DNA) and ribonucleic (RNA). They differ in composition, structure and function. DNA is double-stranded and RNA is single-stranded. The content of nucleic acids in living matter is from 1 to 2%.

Nucleic acids are biopolymers that reach enormous sizes. The length of their molecules is hundreds of thousands of nanometers (1 nm = 10 -9 m), which is thousands of times longer than the length of protein molecules. The DNA molecule is especially large. The molecular weight of nucleic acids reaches tens of millions and billions (10 5 -10 9). For example, the mass of E. coli DNA is 2.5x10 9, and in the nucleus of a human germ cell (haploid set of chromosomes), the length of DNA molecules is 102 cm.

2. NC - non-periodic polymers. Types of nucleotides and their structure

Nucleic acids are non-periodic biopolymers whose polymer chains are formed by monomers called nucleotides. DNA and RNA molecules contain four types of nucleotides. DNA nucleotides are called deoxyribonucleotides, and RNA are called ribonucleotides. The nucleotide composition of DNA and RNA reflect the data in the table.

Table 7. Composition of DNA and RNA nucleotides

Consider the structure of a nucleotide. Nucleotides are complex organic compounds that include three components. The structure of a DNA nucleotide is shown in the figure.

1. Nitrogenous bases have a cyclic structure, which, along with carbon atoms, includes atoms of other elements, in particular nitrogen. For the presence of nitrogen atoms in these compounds, they received the name "nitrogenous", and since they have alkaline properties - "bases". The nitrogenous bases of nucleic acids belong to the classes of pyrimidines and purines. Pyrimidine bases are derivatives of pyrimidine, which has one ring in its molecule. Deoxyribonucleotides contain pyrimidine bases thymine and cytosine, and in the composition of ribonucleotides - cytosine and uracil. Uracil differs from thymine in the absence of a methyl group (–CH 3).

Purine bases are derivatives of purine, which has two rings. Purine bases are adenine and guanine. They are part of the nucleotides of both DNA and RNA.

2. Carbohydrate - pentose (C 5 ). This component also takes part in the formation of nucleotides. DNA nucleotides contain pentose - deoxyribose, and RNA nucleotides contain ribose. The carbohydrate composition of nucleotides is reflected, as we see, in the names of nucleic acids: deoxyribonucleic and ribonucleic. Compounds of pentose with a nitrogenous base are called "nucleosides".

3. rest of phosphoric acid. Phosphate imparts acidic properties to nucleic acids.

So, a nucleotide is made up of a nitrogenous base, a pentose, and a phosphate. In the composition of nucleotides, a nitrogenous base is attached to the carbohydrate on one side, and a phosphoric acid residue on the other.

To be continued

The structure of protein molecules. Connection of properties, functions and activity of proteins with their structural organization (specificity, species affiliation, recognition effect, dynamism, effect of cooperative interaction).

Squirrels - These are high-molecular nitrogen-containing substances, consisting of amino acid residues linked by peptide bonds. Proteins are otherwise called proteins;

Simple proteins are built from amino acids and, upon hydrolysis, break down, respectively, only into amino acids. Complex proteins are two-component proteins that consist of some simple protein and a non-protein component called a prosthetic group. During the hydrolysis of complex proteins, in addition to free amino acids, the non-protein part or its decay products are released. Simple proteins, in turn, are divided on the basis of some conditionally selected criteria into a number of subgroups: protamines, histones, albumins, globulins, prolamins, glutelins, etc.

The classification of complex proteins is based on the chemical nature of their non-protein component. In accordance with this, there are: phosphoproteins (contain phosphoric acid), chromoproteins (they include pigments), nucleoproteins (contain nucleic acids), glycoproteins (contain carbohydrates), lipoproteins (contain lipids) and metalloproteins (contain metals).

3. Protein structure.

The sequence of amino acid residues in the polypeptide chain of a protein molecule is called protein primary structure. The primary structure of a protein, in addition to a large number of peptide bonds, usually also contains a small number of disulfide (-S-S-) bonds. The spatial configuration of the polypeptide chain, more precisely the type polypeptide helix, determinessecondary protein structure, it is presented in mostly α-helix, which is fixed by hydrogen bonds. tertiary structure-polypeptide chain, wholly or partially coiled, is located or packaged in space (in a globule). The known stability of the protein tertiary structure is provided by hydrogen bonds, intermolecular van der Waals forces, electrostatic interaction of charged groups, etc.

Quaternary protein structure - a structure consisting of a certain number of polypeptide chains occupying a strictly fixed position relative to each other.

The classic example of a protein having a quaternary structure is hemoglobin.

Physical properties of proteins: high viscosity solutions,

negligible diffusion, large swelling capacity, optical activity, mobility in an electric field, low osmotic pressure and high oncotic pressure, ability to absorb UV rays at 280 nm, like amino acids, are amphoteric due to the presence of free NH2- and COOH-groups and are characterized, respectively, by all St. you acids and bases. They have pronounced hydrophilic properties. Their solutions have a very low osmotic pressure, high viscosity and little diffusivity. Proteins are capable of swelling to a very large extent. The phenomenon of light scattering, which underlies the quantitative determination of proteins by nephelometry, is associated with the colloidal state of proteins.

Proteins are able to adsorb low molecular weight organic compounds and inorganic ions on their surface. This property determines the transport functions of individual proteins.

Chemical properties of proteins are diverse, since the side radicals of amino acid residues contain various functional groups (-NH2, -COOH, -OH, -SH, etc.). A characteristic reaction for proteins is the hydrolysis of peptide bonds. Due to the presence of both amino and carboxyl groups, proteins have amphoteric properties.

Protein denaturation- destruction of bonds that stabilize the quaternary, tertiary and secondary structures, leading to disorientation of the configuration of the protein molecule and accompanied by the loss of native properties.

There are physical (temperature, pressure, mechanical impact, ultrasonic and ionizing radiation) and chemical (heavy metals, acids, alkalis, organic solvents, alkaloids) factors that cause denaturation.

The reverse process is renaturation, that is, the restoration of the physicochemical and biological properties of the protein. Renaturation is not possible if the primary structure is affected.

Most proteins denature when heated with a solution above 50-60 ° C. External manifestations of denaturation are reduced to a loss of solubility, especially at the isoelectric point, an increase in the viscosity of protein solutions, an increase in the amount of free functional SH-rpypp and a change in the nature of X-ray scattering, globules of native protein molecules and form random and disordered structures.

contraction function. actin and myosin are specific proteins of muscle tissue. structural function. fibrillar proteins, in particular collagen in connective tissue, keratin in hair, nails, skin, elastin in the vascular wall, etc.

hormonal function. A number of hormones are represented by proteins or polypeptides, such as hormones of the pituitary gland, pancreas, etc. Some hormones are derivatives of amino acids.

Nutritional (reserve) function. reserve proteins that are sources of nutrition for the fetus. The main protein of milk (casein) also performs a mainly nutritional function.

Biological functions of proteins. Diversity of proteins in terms of structural organization and biological function. Polymorphism. Differences in the protein composition of organs and tissues. Changes in the composition in ontogeny and in diseases.

-Degree of difficulty Protein structures are divided into simple and complex. Simple or one-component proteins consist only of the protein part and, when hydrolyzed, give amino acids. To difficult or two-component include proteins, in the composition of which includes a protein and an additional group of non-protein nature, called prosthetic. ( lipids, carbohydrates, nucleic acids can act); respectively, complex proteins are called lipoproteins, glycoproteins, nucleoproteins.

- according to the shape of the protein molecule proteins are divided into two groups: fibrillar (fibrous) and globular (corpuscular). fibrillar proteins characterized by a high ratio of their length to diameter (several tens of units). Their molecules are filamentous and are usually collected in bundles that form fibers. (they are the main components of the outer layer of the skin, forming the protective covers of the human body). They are also involved in the formation of connective tissue, including cartilage and tendons.

The vast majority of natural proteins are globular. For globular proteins characterized by a small ratio of length to diameter of the molecule (several units). Having a more complex conformation, globular proteins are also more diverse.

-In relation to conventionally selected solvents allocate albuminsandglobulins. Albumins dissolve very well in water and concentrated saline solutions. Globulins insoluble in water and in solutions of salts of moderate concentration.

--Functional classification of proteins the most satisfactory, since it is based not on a random sign, but on a performed function. In addition, it is possible to distinguish the similarity of structures, properties and functional activity of specific proteins included in any class.

catalytically active proteins called enzymes. They catalyze almost all chemical transformations in the cell. This group of proteins will be discussed in detail in Chapter 4.

Hormones regulate metabolism within cells and integrate metabolism in various cells of the body as a whole.

Receptors selectively bind various regulators (hormones, mediators) on the surface of cell membranes.

Transport proteins carry out the binding and transport of substances between tissues and through cell membranes.

Structural proteins . First of all, this group includes proteins involved in the construction of various biological membranes.

Squirrels - inhibitors enzymes constitute a large group of endogenous inhibitors. They regulate the activity of enzymes.

Contractile squirrels provide a mechanical reduction process using chemical energy.

Toxic proteins - some proteins and peptides secreted by organisms (snakes, bees, microorganisms) that are poisonous to other living organisms.

protective proteins. antibodies - protein substances produced by an animal organism in response to the introduction of an antigen. Antibodies, interacting with antigens, deactivate them and thereby protect the body from the effects of foreign compounds, viruses, bacteria, etc.

The protein composition depends on the physiology. Activity, food composition and diet, biorhythms. In the process of development, the composition changes significantly (from the zygote to the formation of differentiated organs with specialized functions). For example, erythrocytes contain hemoglobin, which provides oxygen transport by blood, mice cells contain contractile proteins actin and myosin, rhodopsin is a protein in the retina, etc. In diseases, the protein composition changes - proteinopathy. Hereditary proteinopathies develop as a result of damage to the genetic apparatus. Any protein is not synthesized at all or is synthesized, but its primary structure is changed (sickle cell anemia). Any disease is accompanied by a change in the protein composition i.e. acquired proteinopathy develops. In this case, the primary structure of proteins is not disturbed, but a quantitative change in proteins occurs, especially in those organs and tissues in which the pathological process develops. For example, with pancreatitis, the production of enzymes necessary for the digestion of nutrients in the gastrointestinal tract decreases.

Factors of damage to the structure and function of proteins, the role of damage in the pathogenesis of diseases. Proteinopathy

The protein composition of the body of a healthy adult is relatively constant, although changes in the amount of individual proteins in organs and tissues are possible. In various diseases, there is a change in the protein composition of tissues. These changes are called proteinopathies. There are hereditary and acquired proteinopathies. Hereditary proteinopathies develop as a result of damage in the genetic apparatus of a given individual. Any protein is not synthesized at all or is synthesized, but its primary structure is changed. Any disease is accompanied by a change in the protein composition of the body, i.e. acquired proteinopathy develops. In this case, the primary structure of proteins is not disturbed, but usually there is a quantitative change in proteins, especially in those organs and tissues in which the pathological process develops. For example, with pancreatitis, the production of enzymes necessary for the digestion of nutrients in the gastrointestinal tract decreases.

In some cases, acquired proteinopathies develop as a result of changes in the conditions in which proteins function. So, when the pH of the medium changes to the alkaline side (alkaloses of various nature), the conformation of hemoglobin changes, its affinity for O 2 increases and the delivery of O 2 to tissues decreases (tissue hypoxia).

Sometimes, as a result of the disease, the level of metabolites in cells and blood serum increases, which leads to the modification of some proteins and disruption of their function.

In addition, proteins can be released from the cells of the damaged organ into the blood, which are normally determined there only in trace amounts. In various diseases, biochemical studies of the protein composition of the blood are often used to clarify the clinical diagnosis.

4. Primary structure of proteins. Dependence of the properties and functions of proteins on their primary structure. Changes in the primary structure, proteinopathy.