A message on the topic of providing cells with energy. Providing cells with energy. Energy sources. Are there other ways to obtain energy?

The ability to photosynthesize is the main characteristic of green plants. Plants, like all living organisms, must eat, breathe, remove unnecessary substances, grow, reproduce, respond to environmental changes. All this is ensured by the work of the relevant organs of the body. Typically, organs form systems of organs that work together to ensure the performance of one or another function of a living organism. Thus, a living organism can be represented as a biosystem. Each organ in a living plant performs a specific job. Root absorbs water with minerals from the soil and strengthens the plant in the soil. The stem carries the leaves towards the light. Water, as well as mineral and organic substances, move along the stem. In leaf chloroplasts, in the light, organic substances are formed from inorganic substances, which they feed on. cells all organs plants. Leaves evaporate water.

If the functioning of any one organ of the body is disrupted, this can cause disruption of the functioning of other organs and the entire body. If, for example, water stops flowing through the root, the entire plant may die. If a plant does not produce enough chlorophyll in its leaves, then it will not be able to synthesize a sufficient amount of organic substances for its vital functions.

Thus, the vital activity of the body is ensured by the interconnected work of all organ systems. Life activity is all the processes that occur in the body.

Thanks to nutrition, the body lives and grows. During nutrition, necessary substances are absorbed from the environment. They are then absorbed in the body. Plants absorb water and minerals from the soil. Aboveground green organs of plants absorb carbon dioxide from the air. Water and carbon dioxide are used by plants to synthesize organic substances, which are used by the plant to renew body cells, grow and develop.

Gas exchange occurs during breathing. Oxygen is absorbed from the environment, and carbon dioxide and water vapor are released from the body. All living cells need oxygen to produce energy.

During the metabolic process, substances that the body does not need are formed and released into the environment.

When a plant reaches a certain size and age required for its species, if it is in sufficiently favorable environmental conditions, then it begins to reproduce. As a result of reproduction, the number of individuals increases.

Unlike the vast majority of animals, plants grow throughout their lives.

The acquisition of new properties by organisms is called development.

Nutrition, respiration, metabolism, growth and development, as well as reproduction are influenced by the plant’s environmental conditions. If they are not favorable enough, then the plant may grow and develop poorly, its vital processes will be suppressed. Thus, the life of plants depends on the environment.

Question 3_Cell membrane, its functions, composition, structure. Primary and secondary shell.

The cell of any organism is an integral living system. It consists of three inextricably linked parts: the membrane, the cytoplasm and the nucleus. The cell membrane directly interacts with the external environment and interacts with neighboring cells (in multicellular organisms). Cell membrane. The cell membrane has a complex structure. It consists of an outer layer and a plasma membrane located underneath it. In plants, as well as in bacteria, blue-green algae and fungi, a dense membrane, or cell wall, is located on the surface of the cells. In most plants it consists of fiber. The cell wall plays an extremely important role: it is an outer frame, a protective shell, and provides turgor for plant cells: water, salts, and molecules of many organic substances pass through the cell wall.

Cell membrane or wall - a rigid cell membrane located outside the cytoplasmic membrane and performing structural, protective and transport functions. Found in most bacteria, archaea, fungi and plants. Animals and many protozoa do not have a cell wall.

Functions of the cell membrane:

1. The transport function provides selective regulation of metabolism between the cell and the external environment, the flow of substances into the cell (due to the semi-permeability of the membrane), as well as regulation of the cell’s water balance

1.1. Transmembrane transport (i.e. across the membrane):
- Diffusion
- Passive transport = facilitated diffusion
- Active = selective transport (involving ATP and enzymes).

1.2. Transport in membrane packaging:
- Exocytosis - release of substances from the cell
- Endocytosis (phago- and pinocytosis) - absorption of substances by the cell

2) Receptor function.
3) Support (“skeleton”)- maintains the shape of the cell, gives strength. This is mainly a function of the cell wall.
4) Cell isolation(its living contents) from the environment.
5) Protective function.
6) Contact with neighboring cells. Combination of cells into tissues.

Energy is necessary for all living cells - it is used for various biological and chemical reactions that occur in the cell. Some organisms use the energy of sunlight for biochemical processes - these are plants (Fig. 1), while others use the energy of chemical bonds in substances obtained during nutrition - these are animal organisms. Energy is extracted by breaking down and oxidizing these substances in the process of respiration, this respiration is called biological oxidation, or cellular respiration.

Rice. 1. Energy from sunlight

Cellular respiration is a biochemical process in a cell that occurs with the participation of enzymes, as a result of which water and carbon dioxide are released, energy is stored in the form of high-energy bonds of ATP molecules. If this process occurs in the presence of oxygen, then it is called aerobic, if it occurs without oxygen, then it is called anaerobic.

Biological oxidation includes three main stages:

1. Preparatory.

2. Oxygen-free (glycolysis).

3. Complete breakdown of organic substances (in the presence of oxygen).

Substances received from food are broken down into monomers. This stage begins in the gastrointestinal tract or in the lysosomes of the cell. Polysaccharides break down into monosaccharides, proteins into amino acids, fats into glycerol and fatty acids. The energy released at this stage is dissipated in the form of heat. It should be noted that for energy processes, cells use carbohydrates, or better yet, monosaccharides, and the brain can only use monosaccharide - glucose - for its work (Fig. 2).

Rice. 2. Preparatory stage

Glucose during glycolysis breaks down into two three-carbon molecules of pyruvic acid. The further fate of pyruvic acid depends on the presence of oxygen in the cell. If oxygen is present in the cell, then pyruvic acid passes into the mitochondria for complete oxidation to carbon dioxide and water (aerobic respiration). If there is no oxygen, then in animal tissues pyruvic acid is converted into lactic acid. This stage takes place in the cytoplasm of the cell.

Glycolysis is a sequence of reactions as a result of which one molecule of glucose is split into two molecules of pyruvic acid, releasing energy that is sufficient to convert two molecules of ADP into two molecules of ATP (Fig. 3).

Rice. 3. Oxygen-free stage

Oxygen is required for complete oxidation of glucose. At the third stage, complete oxidation of pyruvic acid to carbon dioxide and water occurs in mitochondria, resulting in the formation of another 36 ATP molecules, since this stage occurs with the participation of oxygen, it is called oxygen, or aerobic (Fig. 4).

Rice. 4. Complete breakdown of organic substances

In total, the three steps produce 38 ATP molecules from one glucose molecule, taking into account the two ATPs produced during glycolysis.

Thus, we examined the energy processes occurring in cells and characterized the stages of biological oxidation.

Respiration, which occurs in a cell with the release of energy, is often compared to the combustion process. Both processes occur in the presence of oxygen, the release of energy and oxidation products - carbon dioxide and water. But, unlike combustion, respiration is an ordered process of biochemical reactions that occurs in the presence of enzymes. During respiration, carbon dioxide arises as the end product of biological oxidation, and during combustion, the formation of carbon dioxide occurs through the direct combination of hydrogen with carbon. Also, during respiration, in addition to water and carbon dioxide, a certain number of ATP molecules are formed, that is, respiration and combustion are fundamentally different processes (Fig. 5).

Rice. 5. Differences between breathing and combustion

Glycolysis is not only the main pathway for the metabolism of glucose, but also the main pathway for the metabolism of fructose and galactose supplied with food. Particularly important in medicine is the ability of glycolysis to produce ATP in the absence of oxygen. This allows you to maintain intense work of skeletal muscle in conditions of insufficient efficiency of aerobic oxidation. Tissues with increased glycolytic activity are able to remain active during periods of oxygen starvation. In the cardiac muscle, the possibilities for glycolysis are limited. She has a hard time suffering from disruption of the blood supply, which can lead to ischemia. There are several known diseases caused by insufficient activity of glycolytic enzymes, one of which is hemolytic anemia (in fast-growing cancer cells, glycolysis occurs at a rate exceeding the capabilities of the citric acid cycle), which contributes to increased synthesis of lactic acid in organs and tissues (Fig. 6).

Rice. 6. Hemolytic anemia

High levels of lactic acid in the body can be a symptom of cancer. This metabolic feature is sometimes used to treat certain forms of tumors.

Microbes are able to obtain energy during fermentation. Fermentation has been known to people since time immemorial, for example in the production of wine; lactic acid fermentation was known even earlier (Fig. 7).

Rice. 7. Making wine and cheese

People consumed dairy products without realizing that these processes were associated with the activity of microorganisms. The term “fermentation” was introduced by the Dutchman Van Helmont for processes that involve the release of gas. This was first proven by Louis Pasteur. Moreover, different microorganisms secrete different fermentation products. We will talk about alcoholic and lactic acid fermentation. Alcoholic fermentation is the process of oxidation of carbohydrates, which results in the formation of ethyl alcohol, carbon dioxide and the release of energy. Brewers and winemakers have used the ability of certain types of yeast to stimulate fermentation, which converts sugars into alcohol. Fermentation is carried out mainly by yeast, but also by some bacteria and fungi (Fig. 8).

Rice. 8. Yeast, mucor mushrooms, fermentation products - kvass and vinegar

In our country, Saccharomyces yeasts are traditionally used, in America - bacteria from the genus Pseudomonas, in Mexico "moving rod" bacteria are used, in Asia they are used mucor fungi. Our yeast typically ferments hexoses (six-carbon monosaccharides) such as glucose or fructose. The process of alcohol formation can be represented as follows: from one glucose molecule two molecules of alcohol are formed, two molecules of carbon dioxide are formed and two molecules of ATP are released.

C 6 H 12 O 6 → 2C 2 H 5 OH +2CO 2 + 2ATP

Compared to respiration, this process is less energetically beneficial than aerobic processes, but allows life to be maintained in the absence of oxygen. At lactic acid fermentation one molecule of glucose forms two molecules of lactic acid, and at the same time two molecules of ATP are released, this can be described by the equation:

C 6 H 12 O 6 → 2C 3 H 6 O 3 + 2ATP

The process of formation of lactic acid is very close to the process of alcoholic fermentation; glucose, as in alcoholic fermentation, is broken down into pyruvic acid, then it turns not into alcohol, but into lactic acid. Lactic acid fermentation is widely used for the production of dairy products: cheese, cottage cheese, curdled milk, yoghurts (Fig. 9).

Rice. 9. Lactic acid bacteria and products of lactic fermentation

In the process of cheese formation, lactic acid bacteria first participate, which produce lactic acid, then propionic acid bacteria convert lactic acid into propionic acid, due to this the cheeses have a rather specific pungent taste. Lactic acid bacteria are used in the canning of fruits and vegetables, lactic acid is used in the confectionery industry and the production of soft drinks.

Bibliography

1. Mamontov S.G., Zakharov V.B., Agafonova I.B., Sonin N.I. Biology. General patterns. - Bustard, 2009.

2. Ponomareva I.N., Kornilova O.A., Chernova N.M. Fundamentals of general biology. 9th grade: Textbook for 9th grade students of general education institutions / Ed. prof. I.N. Ponomareva. - 2nd ed., revised. - M.: Ventana-Graf, 2005.

3. Pasechnik V.V., Kamensky A.A., Kriksunov E.A. Biology. Introduction to general biology and ecology: Textbook for grade 9, 3rd ed., stereotype. - M.: Bustard, 2002.

1. Website “Biology and Medicine” ()

3. Website “Medical Encyclopedia” ()

Homework

1. What is biological oxidation and its stages?

2. What is glycolysis?

3. What are the similarities and differences between alcoholic and lactic acid fermentation?

The life cycle of a cell clearly demonstrates that the life of a cell is divided into a period of interkinesis and mitosis. During the period of interkinesis, all life processes, except division, are actively carried out. Let's focus on them first. The main life process of a cell is metabolism.

Based on it, the formation of specific substances, growth, differentiation of cells, as well as irritability, movement and self-reproduction of cells occur. In a multicellular organism, the cell is part of the whole. Therefore, the morphological features and nature of all life processes of the cell are formed under the influence of the organism and the surrounding external environment. The body exerts its influence on cells mainly through the nervous system, as well as through the influence of hormones from the endocrine glands.

Metabolism is a certain order of transformation of substances, leading to the preservation and self-renewal of the cell. In the process of metabolism, on the one hand, substances enter the cell that are processed and become part of the cell body, and on the other hand, substances that are decay products are removed from the cell, that is, the cell and the environment exchange substances. Chemically, metabolism is expressed in chemical reactions following each other in a certain order. Strict order in the transformation of substances is ensured by protein substances - enzymes, which play the role of catalysts. Enzymes are specific, that is, they act in a certain way only on certain substances. Under the influence of enzymes, of all possible transformations, this substance changes many times faster in only one direction. The new substances formed as a result of this process change further under the influence of other, equally specific enzymes, etc.

The driving principle of metabolism is the law of unity and struggle of opposites. Indeed, metabolism is determined by two contradictory and at the same time unified processes - assimilation and dissimilation. Substances received from the external environment are processed by the cell and converted into substances characteristic of the cell (assimilation). Thus, the composition of its cytoplasm and nuclear organelles is renewed, trophic inclusions are formed, secretions and hormones are produced. Assimilation processes are synthetic; they occur when energy is absorbed. The source of this energy is the processes of dissimilation. As a result, their previously formed organic substances are destroyed, energy is released and products are formed, some of which are synthesized into new cell substances, while others are removed from the cell (excreta). The energy released as a result of dissimilation is used during assimilation. Thus, assimilation and dissimilation are two, although different, but closely related to each other aspects of metabolism.

The nature of metabolism varies not only among different animals, but even within the same organism in different organs and tissues. This specificity is manifested in the fact that the cells of each organ are capable of assimilating only certain substances, building from them specific substances of their body and releasing quite specific substances into the external environment. Along with the metabolism, energy exchange also occurs, that is, the cell absorbs energy from the external environment in the form of heat, light and, in turn, releases radiant and other types of energy.

Metabolism consists of a number of private processes. The main ones:

1) penetration of substances into the cell;

2) their “processing” using the processes of nutrition and respiration (aerobic and anaerobic);

3) the use of “processed” products for various synthetic processes, an example of which may be protein synthesis and the formation of secretions;

4) removal of waste products from the cell.

The plasmalemma plays an important role in the penetration of substances, as well as in the removal of substances from the cell. Both of these processes can be considered from a physicochemical and morphological point of view. Permeability occurs through passive and active transport. The first occurs due to the phenomena of diffusion and osmosis. However, substances can enter the cell contrary to these laws, which indicates the activity of the cell itself and its selectivity. It is known, for example, that sodium ions are pumped out of the cell, even if their concentration in the external environment is higher than in the cell, and potassium ions, on the contrary, are pumped into the cell. This phenomenon is described as the “sodium-potassium pump” and is accompanied by energy expenditure. The ability to penetrate a cell decreases as the number of hydroxyl groups (OH) in the molecule increases when an amino group (NH2) is introduced into the molecule. Organic acids penetrate more easily than inorganic acids. Ammonia penetrates especially quickly from alkalis. The size of the molecule also matters for permeability. The permeability of a cell changes depending on the reaction, temperature, lighting, age and physiological state of the cell itself, and these reasons can increase the permeability of some substances and at the same time weaken the permeability of others.

The morphological picture of the permeability of substances from the environment is well traced and is carried out through phagocytosis (phagein - devour) and pinocytosis (pynein - drink). The mechanisms of both are apparently similar and differ only quantitatively. With the help of phagocytosis, larger particles are captured, and with the help of pinocytosis, smaller and less dense particles are captured. First, the substances are adsorbed by the surface of the plasmalemma coated with mucopolysaccharides, then together with it they sink deeper, and a bubble is formed, which is then separated from the plasmalemma (Fig. 19). The processing of infiltrated substances is carried out during processes reminiscent of digestion and culminating in the formation of relatively simple substances. Intracellular digestion begins with the fact that phagocytotic or pinocytotic vesicles merge with primary lysosomes, which contain digestive enzymes, and a secondary lysosome, or digestive vacuole, is formed. In them, with the help of enzymes, substances are decomposed into simpler ones. Not only lysosomes, but also other cell components take part in this process. Thus, mitochondria provide the energy side of the process; channels of the cytoplasmic reticulum can be used for transport of processed substances.

Intracellular digestion ends with the formation, on the one hand, of relatively simple products from which newly synthesized complex substances (proteins, fats, carbohydrates) are used to renew cellular structures or form secretions, and on the other hand, products that are to be excreted from the cell as excreta. Examples of the use of processed products include protein synthesis and the formation of secretions.

Rice. 19. Scheme of pinocytosis:

L - formation of pinocytosis channel (1) and pinocytosis vesicles (2). Arrows indicate the direction of plasmalemma invagination. B-G - successive stages of pinocytosis; 3 - adsorbed particles; 4 - particles captured by cell outgrowths; 5 - plasma membrane cells; D, E, B - successive stages of the formation of a pinocytotic vacuole; F - food particles are freed from the vacuole shell.

Protein synthesis occurs on ribosomes and conventionally occurs in four stages.

The first stage involves the activation of amino acids. Their activation occurs in the cytoplasmic matrix with the participation of enzymes (aminoacyl - RNA synthetases). About 20 enzymes are known, each of which is specific for only one amino acid. Activation of an amino acid occurs when it combines with an enzyme and ATP.

As a result of the interaction, pyrophosphate is split off from ATP, and the energy located in the bond between the first and second phosphate groups is transferred entirely to the amino acid. The amino acid activated in this way (aminoacyl adenylate) becomes reactive and acquires the ability to combine with other amino acids.

The second stage is the binding of the activated amino acid to transfer RNA (tRNA). In this case, one tRNA molecule attaches only one molecule of activated amino acid. These reactions involve the same enzyme as in the first stage, and the reaction ends with the formation of a t-RNA complex and an activated amino acid. The tRNA molecule consists of a double short helix closed at one end. The closed (head) end of this helix is ​​represented by three nucleotides (anticodon), which determine the attachment of this t-RNA to a specific section (codon) of a long messenger RNA (i-RNA) molecule. An activated amino acid is attached to the other end of the tRNA (Fig. 20). For example, if a tRNA molecule has a UAA triplet at the head end, then only the amino acid lysine can attach to its opposite end. Thus, each amino acid has its own special tRNA. If the three terminal nucleotides in different tRNAs are the same, then its specificity is determined by the sequence of nucleotides in another region of the tRNA. The energy from the activated amino acid coupled to the tRNA is used to form peptide bonds in the polypeptide molecule. The activated amino acid is transported by tRNA through the hyaloplasm to the ribosomes.

The third stage is the synthesis of polypeptide chains. Messenger RNA, leaving the nucleus, is pulled through the small subunits of several ribosomes of a particular polyribosome, and in each of them the same synthesis processes are repeated. During broaching, the molecular

Rice. 20. Scheme of polypeptide synthesis on ribosomes using mRNA and t-RNA: /, 2-ribosome; 3 - tRNA carrying anticodons at one end: ACC, AUA. Ayv AGC, and at the other end, respectively, amino acids: tryptophan, roller, lysine, serine (5); 4-nRNA, in which the codes are located: UGG (tryptophan)” URU (valine). UAA (lysine), UCG (serine); 5 - synthesized polypeptide.

A t-RNA code, the triplet of which corresponds to the i-RNA code word. The codeword then moves to the left, and with it the tRNA attached to it. The amino acid brought by it is connected by a peptide bond to the previously brought amino acid of the synthesizing polypeptide; t-RNA is separated from i-RNA, translation (copying) of i-RNA information occurs, that is, protein synthesis. Obviously, two tRNA molecules are simultaneously attached to ribosomes: one at the site that carries the polypeptide chain being synthesized, and the other at the site to which the next amino acid is attached before it takes its place in the chain.

The fourth stage is the removal of the polypeptide chain from the ribosome and the formation of a spatial configuration characteristic of the synthesized protein. Finally, the protein molecule that has completed its formation becomes independent. t-RNA can be used for repeated synthesis, and mRNA is destroyed. The duration of the formation of a protein molecule depends on the number of amino acids in it. It is believed that the addition of one amino acid lasts 0.5 seconds.

The synthesis process requires energy, the source of which is ATP, which is formed mainly in mitochondria and in small quantities in the nucleus, and with increased cell activity also in the hyaloplasm. In the nucleus in the hyaloplasm, ATP is formed not on the basis of the oxidative process, as in mitochondria, but on the basis of glycolysis, that is, an anaerobic process. Thus, synthesis is carried out thanks to the coordinated work of the nucleus, hyaloplasm, ribosomes, mitochondria and granular cytoplasmic reticulum of the cell.

The secretory activity of a cell is also an example of the coordinated work of a number of cellular structures. Secretion is the production by a cell of special products, which in a multicellular organism are most often used in the interests of the whole organism. Thus, saliva, bile, gastric juice and other secretions serve to process food into

Rice. 21. Scheme of one of the possible ways of secretion synthesis in a cell and its removal:

1 - secreted in the core; 2 - pro-secret exit from the kernel; 3 - accumulation of prosecrete in the cytoplasmic reticulum tank; 4 - separation of the secretion tank from the cytoplasmic reticulum; 5 - lamellar complex; 6 - a drop of secretion in the area of ​​the lamellar complex; 7- mature secretion granule; 8-9 - successive stages of secretion; 10 - secretion outside the cell; 11 - plasmalemma of the cell.

Digestive organs. Secretions can be formed either only by proteins (a number of hormones, enzymes), or consist of glycoproteins (mucus), ligyu-proteins, glycolipoproteins, less often they are represented by lipids (milk fat and sebaceous glands) or inorganic substances (hydrochloric acid of the fundic glands).

In secretory cells, two ends can usually be distinguished: basal (facing the pericapillary space) and apical (facing the space where the secretion is released). Zoning is observed in the arrangement of the components of the secretory cell, and from the basal to the apical ends (poles) they form the following row: granular cytoplasmic reticulum, nucleus, lamellar complex, secretion granules (Fig. 21). The plasmalemma of the basal and apical poles often bears microvilli, as a result of which the surface area for the entry of substances from the blood and lymph through the basal pole and the exit of the finished secretion through the apical pole increases.

When a secretion of a protein nature is formed (pancreas), the process begins with the synthesis of proteins specific to the secretion. Therefore, the nucleus of secretory cells is rich in chromatin and has a well-defined nucleolus, thanks to which all three types of RNA are formed, entering the cytoplasm and participating in protein synthesis. Sometimes, apparently, the synthesis of the secretion begins in the nucleus and ends in the cytoplasm, but most often in the hyaloplasm and continues in the granular cytoplasmic reticulum. The tubules of the cytoplasmic reticulum play an important role in the accumulation of primary products and their transport. In this regard, secretory cells have many ribosomes and a well-developed cytoplasmic reticulum. Sections of the cytoplasmic reticulum with the primary secretion are torn off and directed to the lamellar complex, passing into its vacuoles. Here the formation of secretory granules occurs.

At the same time, a lipoprotein membrane is formed around the secretion, and the secretion itself matures (loses water), becoming more concentrated. The finished secretion in the form of granules or vacuoles leaves the lamellar complex and is released out through the apical pole of the cells. Mitochondria provide energy for this entire process. Secrets of a non-protein nature are apparently synthesized in the cytoplasmic reticulum and, in some cases, even in mitochondria (lipid secretions). The secretion process is regulated by the nervous system. In addition to constructive proteins and secretions, as a result of metabolism in the cell, substances of a trophic nature (glycogen, fat, pigments, etc.) can be formed and energy (radiant, thermal and electrical biocurrents) can be produced.

Metabolism is completed by the release of a number of substances into the external environment, which, as a rule, are not used by the cell and are often

Even harmful for her. The removal of substances from the cell is carried out, like the entry, on the basis of passive physico-chemical processes (diffusion, osmosis), and by active transfer. The morphological picture of excretion often has a character opposite to phagocytosis. The excreted substances are surrounded by a membrane.

The resulting bubble approaches the cell membrane, comes into contact with it, then breaks through, and the contents of the bubble appear outside the cell.

Metabolism, as we have already said, determines other vital manifestations of the cell, such as cell growth and differentiation, irritability, and the ability of cells to reproduce themselves.

Cell growth is an external manifestation of metabolism, expressed in an increase in cell size. Growth is possible only if, in the process of metabolism, assimilation prevails over dissimilation, and each cell grows only to a certain limit.

Cell differentiation is a series of qualitative changes that occur differently in different cells and are determined by the environment and the activity of DNA sections called genes. As a result, different quality cells of various tissues arise; subsequently, the cells undergo age-related changes, which are little studied. However, it is known that cells are depleted of water, protein particles become larger, which entails a decrease in the total surface of the dispersed phase of the colloid and, as a consequence, a decrease in the metabolic rate. Therefore, the vital potential of the cell decreases, oxidative, reduction and other reactions slow down, the direction of some processes changes, which is why various substances accumulate in the cell.

The irritability of a cell is its reaction to changes in the external environment, due to which temporary contradictions that arise between the cell and the environment are eliminated, and the living structure becomes adapted to the already changed external environment.

The following points can be distinguished in the phenomenon of irritability:

1) exposure to an environmental agent (for example, mechanical, chemical, radiation, etc.)

2) the transition of the cell to an active, that is, excitable, state, which is manifested in changes in biochemical and biophysical processes inside the cell, and cell permeability and oxygen absorption may increase, the colloidal state of its cytoplasm may change, electric currents of action may appear, etc.;

3) the cell’s response to the influence of the environment, and in different cells the response manifests itself differently. Thus, a local change in metabolism occurs in the connective tissue, contraction occurs in the muscle tissue, secretions are released in the glandular tissues (saliva, bile, etc.), a nerve impulse occurs in the nerve cells, and in the glandular epithelium, muscle and nervous tissues, excitation arises in one area, spreads throughout the tissue. In a nerve cell, excitation can spread not only to other elements of the same tissue (resulting in the formation of complex excitable systems - reflex arcs), but also to move to other tissues. Thanks to this, the regulatory role of the nervous system is carried out. The degree of complexity of these reactions depends on the level of organization of the animal. Depending on the strength and nature of the irritating agent, the following three types of irritability are distinguished: normal, state of paranecrosis and necrotic. If the strength of the stimulus does not go beyond the normal limits inherent in the environment in which the cell or the organism as a whole lives, then the processes occurring in the cell ultimately eliminate the contradiction with the external environment, and the cell returns to a normal state. In this case, no disruption of the cell structure visible under a microscope occurs. If the strength of the stimulus is great or it affects the cell for a long time, then a change in intracellular processes leads to a significant disruption of the function, structure and chemistry of the cell. Inclusions appear in it, structures are formed in the form of threads, lumps, meshes, etc. The reaction of the cytoplasm shifts towards acidity, a change in the structure and physicochemical properties of the cell disrupts the normal functioning of the cell, putting it on the brink of life and death. Nasonov and Aleksandrov called this condition paranecrotic* It is reversible and can result in the restoration of the cell, but it can also lead to its death. Finally, if the agent acts with very great force, the processes inside the cell are so severely disrupted that restoration is impossible, and the cell dies. After this, a series of structural changes occur, that is, the cell enters a state of necrosis or necrosis.

Movement. The nature of movement inherent in a cell is very diverse. First of all, the cell undergoes continuous movement of the cytoplasm, which is obviously associated with the implementation of metabolic processes. Further, various cytoplasmic formations can move very actively in the cell, for example, cilia in the ciliated epithelium, mitochondria; makes movement and the core. In other cases, movement is expressed in a change in the length or volume of the cell with its subsequent return to its original position. This movement is observed in muscle cells, muscle fibers and pigment cells. Movement in space is also widespread. It can be carried out with the help of pseudopods, like in an amoeba. This is how leukocytes and some cells of connective and other tissues move. Spermin have a special form of movement in space. Their forward movement occurs due to a combination of serpentine bends of the tail and rotation of the sperm around the longitudinal axis. In relatively simply organized creatures and in some cells of highly organized multicellular animals, movement in space is caused and directed by various agents of the external environment and is called taxis.

There are: chemotaxis, thigmotaxis and rheotaxis. Chemotaxis is movement towards or away from chemicals. Such taxis is detected by blood leukocytes, which move amoebically towards bacteria that have entered the body and secrete certain substances. Thigmotaxis is movement towards or away from a touched solid body. For example, lightly touching food particles to an amoeba causes it to envelop them and then swallow them. Strong mechanical irritation can cause movement in the direction opposite to the irritating origin. Rheotaxis is movement against the flow of fluid. Spermine, which moves in the uterus against the flow of mucus towards the egg cell, has the ability to rheotaxis.

The ability to reproduce itself is the most important property of living matter, without which life is impossible. Every living system is characterized by a chain of irreversible changes that culminate in death. If these systems did not give rise to new systems capable of starting the cycle over again, life would cease.

The cell's self-reproduction function is carried out through division, which is a consequence of cell development. During its life, due to the predominance of assimilation over dissimilation, the mass of cells increases, but the volume of the cell increases faster than its surface. Under these conditions, the intensity of metabolism decreases, deep physical-chemical and morphological changes in the cell occur, and assimilation processes are gradually inhibited, which has been convincingly proven with the help of labeled atoms. As a result, the growth of the cell first stops, and then its further existence becomes impossible, and division occurs.

The transition to division is a qualitative leap, or a consequence of quantitative changes in assimilation and dissimilation, a mechanism for resolving contradictions between these processes. After division, the cells seem to rejuvenate, their vital potential increases, since due to the decrease in size, the proportion of the active surface increases, the metabolism in general and its assimilation phase in particular are intensified.

Thus, the individual life of a cell consists of a period of interphase, characterized by increased metabolism, and a period of division.

Interphase is divided with some degree of convention:

1) for the presynthetic period (Gj), when the intensity of assimilation processes gradually increases, but DNA reduplication has not yet begun;

2) synthetic (S), characterized by the height of synthesis, during which DNA doubling occurs, and

3) postsynthetic (G2), when the processes of DNA synthesis stop.

The following main types of division are distinguished:

1) indirect division (mitosis, or karyokinesis);

2) meiosis, or reduction division, and

3) amitosis, or direct division.

Detailed solution paragraph Summarize chapter 2 of biology for 11th grade students, authors I.N. Ponomareva, O.K. Kornilova, T.E. Loshchilina, P.V. Izhevsk Basic level 2012

• GD in Biology for grade 11 can be found
• Gdz workbook on Biology for grade 11 can be found

1. Formulate a definition of the “cell” biosystem..

A cell is an elementary living system, the basic structural unit of living organisms, capable of self-renewal, self-regulation and self-reproduction.

2. Why is the cell called the basic form of life and the elementary unit of life?

The cell is the basic form of life and the elementary unit of life, because any organism consists of cells, and the smallest organism is a cell (protozoa). Individual organelles cannot live outside the cell.

The following processes occur at the cellular level: metabolism (metabolism); absorption and, therefore, incorporation of various chemical elements of the Earth into the contents of living things; transfer of hereditary information from cell to cell; accumulation of changes in the genetic apparatus as a result of interaction with the environment; response to irritations when interacting with the external environment. The structural elements of the cellular level system are various complexes of molecules of chemical compounds and all the structural parts of the cell - the surface apparatus, the nucleus and the cytoplasm with their organelles. The interaction between them ensures the unity and integrity of the cell in the manifestation of its properties as a living system in relations with the external environment.

3. Explain the mechanisms of cell stability as a biosystem.

A cell is an elementary biological system, and any system is a complex of interconnected and interacting components that make up a single whole. In a cell, these components are organelles. The cell is capable of metabolism, self-regulation and self-renewal, due to which its stability is maintained. The entire genetic program of the cell is located in the nucleus, and various deviations from it are perceived by the cell’s enzymatic system.

4. Compare eukaryotic and prokaryotic cells.

All living organisms on Earth are divided into two groups: prokaryotes and eukaryotes.

Eukaryotes are plants, animals and fungi.

Prokaryotes are bacteria (including cyanobacteria (blue-green algae).

The main difference. Prokaryotes do not have a nucleus; circular DNA (circular chromosome) is located directly in the cytoplasm (this section of the cytoplasm is called the nucleoid). Eukaryotes have a formed nucleus (hereditary information [DNA] is separated from the cytoplasm by the nuclear envelope).

Other differences.

Since prokaryotes do not have a nucleus, they do not have mitosis/meiosis. Bacteria reproduce by fission in two, budding

Eukaryotes have different numbers of chromosomes, depending on the species. Prokaryotes have a single chromosome (ring-shaped).

Eukaryotes have organelles surrounded by membranes. Prokaryotes do not have organelles surrounded by membranes, i.e. there is no endoplasmic reticulum (its role is played by numerous protrusions of the cell membrane), no mitochondria, no plastids, no cell center.

A prokaryotic cell is much smaller than a eukaryotic cell: 10 times in diameter, 1000 times in volume.

Similarity. The cells of all living organisms (all kingdoms of living nature) contain a plasma membrane, cytoplasm and ribosomes.

5. Describe the intracellular structure of eukaryotes.

The cells that form the tissues of animals and plants vary significantly in shape, size and internal structure. However, they all show similarities in the main features of life processes, metabolism, irritability, growth, development, and the ability to change.

Cells of all types contain two main components, closely related to each other - the cytoplasm and the nucleus. The nucleus is separated from the cytoplasm by a porous membrane and contains nuclear sap, chromatin and the nucleolus. Semi-liquid cytoplasm fills the entire cell and is penetrated by numerous tubules. On the outside it is covered with a cytoplasmic membrane. It contains specialized organelle structures that are constantly present in the cell, and temporary formations - inclusions. Membrane organelles: cytoplasmic membrane (CM), endoplasmic reticulum (ER), Golgi apparatus, lysosomes, mitochondria and plastids. The structure of all membrane organelles is based on a biological membrane. All membranes have a fundamentally uniform structural plan and consist of a double layer of phospholipids, into which protein molecules are immersed from different sides to different depths. The membranes of organelles differ from each other only in the sets of proteins they contain.

6. How is the “cell - from cell” principle implemented?

Reproduction of prokaryotic and eukaryotic cells occurs only through division of the original cell, which is preceded by the reproduction of its genetic material (DNA reduplication).

In eukaryotic cells, the only complete method of division is mitosis (or meiosis in the formation of germ cells). In this case, a special cell division apparatus is formed - the cell spindle, with the help of which chromosomes, which previously doubled in number, are distributed evenly and accurately among the two daughter cells. This type of division is observed in all eukaryotic cells, both plant and animal.

Prokaryotic cells, which divide in the so-called binary manner, also use a special cell division apparatus that is significantly reminiscent of the mitotic method of division of eukaryotes. Also dividing the mother cell in two.

7. Describe the phases and significance of mitosis.

The process of mitosis is usually divided into four main phases: prophase, metaphase, anaphase and telophase. Since it is continuous, the change of phases is carried out smoothly - one imperceptibly passes into the other.

In prophase, the volume of the nucleus increases, and due to the spiralization of chromatin, chromosomes are formed. By the end of prophase, it is clear that each chromosome consists of two chromatids. The nucleoli and nuclear membrane gradually dissolve, and the chromosomes appear randomly located in the cytoplasm of the cell. Centrioles diverge towards the poles of the cell. An achromatin fission spindle is formed, some of the threads of which go from pole to pole, and some are attached to the centromeres of the chromosomes. The content of genetic material in the cell remains unchanged (2n4c).

In metaphase, chromosomes reach maximum spiralization and are arranged in an orderly manner at the equator of the cell, so they are counted and studied during this period. The content of genetic material does not change (2n4c).

In anaphase, each chromosome “splits” into two chromatids, which are then called daughter chromosomes. The spindle strands attached to the centromeres contract and pull the chromatids (daughter chromosomes) toward opposite poles of the cell. The content of genetic material in the cell at each pole is represented by a diploid set of chromosomes, but each chromosome contains one chromatid (4n4c).

In telophase, the chromosomes located at the poles despiral and become poorly visible. Around the chromosomes at each pole, a nuclear membrane is formed from membrane structures of the cytoplasm, and nucleoli are formed in the nuclei. The fission spindle is destroyed. At the same time, the cytoplasm is dividing. Daughter cells have a diploid set of chromosomes, each of which consists of one chromatid (2n2c).

The biological significance of mitosis is that it ensures the hereditary transmission of characteristics and properties in a series of cell generations during the development of a multicellular organism. Due to the precise and uniform distribution of chromosomes during mitosis, all cells of a single organism are genetically identical.

Mitotic cell division underlies all forms of asexual reproduction in both unicellular and multicellular organisms. Mitosis determines the most important phenomena of life: growth, development and restoration of tissues and organs and asexual reproduction of organisms.

8. What is the cell cycle?

The cell cycle (mitotic cycle) is the entire period of cell existence from the moment the mother cell appears during division until its own division (including division itself) or death. It consists of interphase and cell division.

9. What role did the cell play in the evolution of organisms?

The cell gave rise to the further development of the organic world. During this evolution, an amazing diversity of cell forms was achieved, multicellularity arose, cell specialization arose, and cellular tissues appeared.

10. Name the main processes of cell life.

Metabolism – nutrients enter the cell and unnecessary ones are removed. Movement of the cytoplasm – transports substances in the cell. Respiration - oxygen enters the cell and carbon dioxide is removed. Nutrition - nutrients enter the cell. Growth - the cell increases in size. Development - the structure of the cell becomes more complex.

11. Indicate the importance of mitosis and meiosis in cell evolution.

Thanks to mitotic cell division, the individual development of the organism occurs - its growth increases, tissues are renewed, aged and dead cells are replaced, and asexual reproduction of organisms occurs. The constancy of the karyotypes of individuals of the species is also ensured.

Thanks to meiosis, crossing over occurs (exchange of sections of homologous chromosomes). This promotes the recombination of genetic information, and cells with a completely new set of genes are formed (diversity of organisms).

12. What are the most important events in the development of living matter that took place at the cellular level during the process of evolution?

Major aromorphoses (mitosis, meiosis, gametes, sexual process, zygote, vegetative and sexual reproduction).

The appearance of nuclei in cells (eukaryotes).

Symbiotic processes in unicellular organisms - the emergence of organelles.

Autotrophy and heterotrophy.

Mobility and immobility.

The emergence of multicellular organisms.

Differentiation of cell functions in multicellular organisms.

13. Describe the general significance of the cellular level of living matter in nature and for humans.

The cell, having once emerged in the form of an elementary biosystem, became the basis for all further development of the organic world. The evolution of bacteria, cyanobacteria, various algae and protozoa occurred entirely due to the structural, functional and biochemical transformations of the primary living cell. During this evolution, an amazing variety of cell forms was achieved, but the general plan of the cell structure did not undergo fundamental changes. In the process of evolution, based on unicellular life forms, multicellularity arose, cell specialization arose, and cellular tissues appeared.

Have your say

1. Why exactly at the cellular level of the organization of life did such properties of living beings arise as autotrophy and heterotrophy, mobility and immobility, multicellularity and specialization in structure and function? What contributed to such events in the life of the cell?

The cell is the basic structural and functional unit of living things. This is a kind of living system, which is characterized by breathing, nutrition, metabolism, irritability, discreteness, openness, and heredity. It was at the cellular level that the first living organisms arose. In a cell, each organelle performs a specific function and has a specific structure; united and functioning together, they represent a single biosystem, which has all the characteristics of a living thing.

The cell, as a multicellular organism, has also evolved over many centuries. Various environmental conditions, natural disasters, and biotic factors have led to the complication of cell organization.

That is why autotrophy and heterotrophy, mobility and immobility, multicellularity and specialization in structure and function arose precisely at the cell level, where all organelles and the cell as a whole exist harmoniously and purposefully.

2. On what basis have all scientists classified cyanobacteria as plants, in particular algae, for a very long time, and only at the end of the 20th century. were they placed in the kingdom of bacteria?

The relatively large size of the cells (nostok, for example, forms quite large colonies that you can even pick up), carry out photosynthesis with the release of oxygen in a manner similar to higher plants, and also the external similarity with algae was the reason for their consideration earlier as part of plants (“blue-green algae ").

And at the end of the twentieth century, it was proven that cells do not have blue-green nuclei, and the chlorophyll in their cells is not the same as in plants, but characteristic of bacteria. Now cyanobacteria are among the most complexly organized and morphologically differentiated prokaryotic microorganisms.

3. What plant and animal cellular tissues are the clothes and shoes you wore to school today made from?

Choose the ones that suit you. You can give a lot of examples. For example, flax (bast fibers - conductive fabric) is used to make fabric with a durable structure (men's shirt, women's suits, underwear, socks, trousers, sundresses). Cotton is used to make underwear, T-shirts, shirts, trousers, sundresses). Shoes (shoes, sandals, boots) and belts are made from animal skin (epithelial tissue). Warm clothing is made from the wool of fur-bearing animals. Sweaters, socks, hats, and mittens are made from wool. Made from silk (the secret of the silkworm glands is connective tissue) - shirts, scarves, underwear.

Problem to discuss

Charles Darwin's grandfather Erasmus Darwin, a physician, naturalist and poet, wrote at the end of the 18th century. the poem “The Temple of Nature,” published in 1803, after his death. Read a short excerpt from this poem and think about what ideas about the role of the cellular level of life can be found in this work (the excerpt is given in the book).

The emergence of earthly life occurred from the smallest cellular forms. It was at the cellular level that the first living organisms arose. The cell, as an organism, also grew and evolved, thereby giving impetus to the formation of many cellular forms. They were able to populate both the “silt” and the “water mass”. Most likely, various environmental conditions, natural disasters, and biotic factors led to a more complex organization of cells, which led to the “acquisition of members” (which implies multicellularity).

Basic Concepts

Prokaryotes, or prenuclear, are organisms whose cells do not have a formed nucleus bounded by a membrane.

Eukaryotes, or nuclear ones, are organisms whose cells have a well-formed nucleus, separated by a nuclear envelope from the cytoplasm.

An organoid is a cellular structure that provides specific functions.

The nucleus is the most important part of a eukaryotic cell, regulating all its activities; carries hereditary information in DNA macromolecules.

A chromosome is a DNA-containing thread-like structure in the cell nucleus that carries genes, units of heredity, arranged in a linear order.

A biological membrane is an elastic molecular structure consisting of proteins and lipids. Separates the contents of any cell from the external environment, ensuring its integrity.

Mitosis (indirect cell division) is a universal method of division of eukaryotic cells, in which daughter cells receive genetic material identical to the original cell.

Meiosis is a method of dividing eukaryotic cells, accompanied by a halving (reduction) of the number of chromosomes; One diploid cell gives rise to four haploid cells.

The cell cycle is the reproductive cycle of a cell, consisting of several sequential events (for example, interphase and mitosis in eukaryotes), during which the contents of the cell are doubled and it divides into two daughter cells.

The cellular structural level of organization of living matter is one of the structural levels of life, the structural and functional unit of which is the organism, and the unit is the cell. The following phenomena occur at the organismal level: reproduction, functioning of the organism as a whole, ontogenesis, etc.

What is the function of DNA in protein synthesis: a) self-duplication; b) transcription; c) synthesis
tRNA and rRNA.
Why
The information of one gene of a DNA molecule corresponds to: a) protein; b) amino acid;
c) gene.
How many
amino acids participate in the biosynthesis of proteins: a) 100; b) 30; in 20.
What
formed on the ribosome during protein biosynthesis: a) tertiary protein
structures; b) secondary structure protein; c) polypeptide chain.
Role
matrices in protein biosynthesis are performed by: a) mRNA; b) tRNA; c) DNA; d) protein.
Structural
The functional unit of genetic information is: a) DNA strand; b)
section of a DNA molecule; c) DNA molecule; d) gene.
mRNA in
in the process of protein biosynthesis: a) accelerates biosynthesis reactions; b) stores
genetic information; c) transmits genetic information; d) is
site of protein synthesis.
Genetic
code is a sequence of: a) nucleotides in rRNA; b) nucleotides in
mRNA; c) amino acids in protein; d) nucleotides in DNA.
Amino acid
attaches to tRNA: a) to any codon; b) to the anticodon; c) to codon b
base of the molecule.
Synthesis
protein occurs in: a) the nucleus; b) cytoplasm; c) on ribosomes; G)
mitochondria.
Broadcast
- this is the process of: a) transport of mRNA to ribosomes; b) ATP transport to
ribosomes; c) transport of amino acids to ribosomes; d) connection
amino acids into a chain.
TO
reactions of plastic exchange in a cell include: a) DNA replication and
protein biosynthesis; b) photosynthesis, chemosynthesis, glycolysis; c) photosynthesis and
biosynthesis; d) biosynthesis, DNA replication, glycolysis.
IN
the functional center of the ribosome during translation is always a number
nucleotides equal to: a) 2; b) 3; at 6; d) 9.
Transcription
and translation in a eukaryotic cell occurs: a) only in the nucleus; b) c
nucleus and cytoplasm; c) in the cytoplasm.
In reactions
protein biosynthesis in the cell, ATP energy: a) is released; b) is spent; V)
is not consumed or released; d) at some stages it is consumed, at others
stands out.
Quantity
combinations of triplets of the genetic code that do not encode any
amino acids is: a) 1; b) 3; at 4.
Subsequence
nucleotides in an mRNA molecule are strictly complementary to: a) sequence
gene triplets; b) a triplet encoding an amino acid; c) codons,
containing information about the structure of the gene; d) codons containing information
about protein structure.
Where
complex structures of protein molecules are formed: a) on the ribosome; b) c
cytoplasm; c) in the endoplasmic reticulum.
What components make up the body of the ribosome: a) membranes; b)
proteins; c) carbohydrates; d) RNA.

The “energy stations” that provide the cell with energy are: 1 vacuole 2 cytoplasm 3 mitochondria. Organelles are located freely or on

rough endoplasmic reticulum, involved in protein biosynthesis: 1ribosomes 2lysosomes 3mitochondria 4centrioles

From the proposed answers, select one of the provisions of the cell theory:

A) organisms of all kingdoms of living nature consist of cells
B) the fungal cell wall consists of chitin, like the exoskeleton of arthropods
C) cells of animal organisms do not contain plastids
D) a bacterial spore is one specialized cell
Water in the cell performs the function of: A) transport, solvent
B) energy C) catalytic D) information
RNA is:
A) a polynucleotide chain in the form of a double helix, the chains of which are connected by hydrogen bonds B) a nucleotide containing two energy-rich bonds
B) a polynucleotide thread in the form of a single-stranded helix
D) a polynucleotide chain consisting of various amino acids
The synthesis of ATP molecules occurs in:
A) ribosomes B) mitochondria C) Golgi apparatus D) ER
Prokaryotic cells differ from eukaryotic cells:
A) larger sizes B) absence of a core
C) the presence of a shell D) the presence of nucleic acids
Mitochondria are considered the powerhouses of the cell because:
A) they break down organic substances to release energy
B) nutrients are stored in them
C) organic substances are formed in them D) they convert light energy
The importance of metabolism in a cell is:
A) providing the cell with building materials and energy
B) the transfer of hereditary information from the maternal organism to the daughter
B) uniform distribution of chromosomes between daughter cells
D) ensuring the interconnections of cells in the body
The role of mRNA in protein synthesis is:
A) ensuring the storage of hereditary information B) providing the cell with energy
C) ensuring the transfer of genetic information from the nucleus to the cytoplasm
Restoration of the diploid set of chromosomes in the zygote - the first cell of a new organism - occurs as a result of:
A) meiosis B) mitosis C) fertilization D) metabolism
“Genes located on the same chromosome are inherited together” is the formulation:
A) G. Mendel’s rules of dominance B) T. Morgan’s law of linked inheritance
C) G. Mendel’s law of segregation D) G. Mendel’s law of independent inheritance of traits
The genetic code is:
A) a segment of a DNA molecule containing information about the primary structure of one protein
B) sequence of amino acid residues in a protein molecule
C) the sequence of nucleotides in a DNA molecule that determines the primary structure of all protein molecules
D) information about the primary structure of the protein encrypted in tRNA
The set of genes of a population, species or other systematic group is called:
A) genotype B) phenotype C) genetic code D) gene pool
Variability that occurs under the influence of environmental factors and does not affect chromosomes and genes is called: A) hereditary B) combinative
C) modification D) mutation
The formation of new species in nature occurs as a result of:
A) the desire of individuals for self-improvement
B) preferential preservation as a result of the struggle for existence and natural selection of individuals with useful hereditary changes:
C) selection and preservation by humans of individuals with useful hereditary changes
D) survival of individuals with various hereditary changes
The process of preserving from generation to generation individuals with hereditary changes beneficial to humans is called: A) natural selection
B) hereditary variability C) struggle for existence D) artificial selection
Identify aromorphoses among the named evolutionary changes:
A) formation of digging-type limbs in a mole
B) the appearance of protective coloring in the caterpillar
C) the appearance of pulmonary respiration in amphibians D) the loss of limbs in whales
Of the listed factors of human evolution, the biological ones include:
A) natural selection B) speech C) social lifestyle D) work
Write down the letters in the sequence that reflects the stages of human evolution: A) Cro-Magnons B) Pithecanthropus C) Neanderthals D) Australopithecus
All components of inanimate nature (light, temperature, humidity, chemical and physical composition of the environment) affecting organisms, populations, communities are called factors:
A) anthropogenic B) abiotic C) limiting D) biotic
Animals and fungi belong to the group of heterotrophs because:
A) they themselves create organic substances from inorganic ones B) they use the energy of sunlight C) they feed on ready-made organic substances D) they feed on mineral substances
Biogeocenosis is:
A) an artificial community created as a result of human economic activity
B) a complex of interrelated species living in a certain territory with homogeneous natural conditions
C) the totality of all living organisms on the planet
D) geological shell inhabited by living organisms
The form of existence of a species, ensuring its adaptability to life in certain conditions, is represented by:
A) individual B) herd C) colony D) population

1. Which of the following statements is considered correct?

a) origin from specialized ancestors;
b) non-directional evolution;
c) limited evolution;
d) progressive specialization.
2. The struggle for existence is a consequence of:
a) an innate desire for perfection;
b) the need to deal with natural disasters;
c) genetic diversity;
d) the fact that the number of descendants exceeds the potential capabilities of the environment.
3.Correct taxonomy in botany:
a) species – genus – family – class – order;
b) genus – family – detachment – ​​class – department;
c) species – genus – family – order – class;
d) species – genus – family – order – type.
4. The mediator in the preganglionic neurons of the sympathetic nervous system is:
a) adrenaline;
b) acetylcholine;
c) serotonin;
d) glycine.
5. Insulin in the human body is not involved in:
a) activation of protein breakdown in cells;
b) protein synthesis from amino acids;
c) energy storage;
d) storage of carbohydrates in the form of glycogen.
6. One of the main sleep-inducing substances is produced by neurons in the central part of the midbrain:
a) norepinephrine;
b) acetylcholine;
c) serotonin;
d) dopamine.
7. Among the water-soluble vitamins, coenzymes are:
a) pantothenic acid;
b) vitamin A;
c) biotin;
d) vitamin K.
8. The following have the ability to phagocytosis:
a) B-lymphocytes;
b) T-killers;
c) neutrophils;
d) plasma cells.
9. The following are involved in the occurrence of tickling and itching sensations:
a) free nerve endings;
b) Ruffini bodies;
c) nerve plexuses around hair follicles;
d) Pacinian corpuscles.
10.What features are typical for all joints?
a) the presence of joint fluid;
b) the presence of a joint capsule;
c) the pressure in the articular cavity is below atmospheric;
d) there are intra-articular ligaments.
11.What processes occurring in skeletal muscles require the expenditure of ATP energy?
a) transport of K+ ions from the cell;
b) transport of Na+ ions into the cell;
c) movement of Ca2+ ions from the EPS tanks into the cytoplasm;
d) rupture of cross bridges between actin and myosin.

12. When a person stays in weightlessness for a long time, the following does not happen:
a) decrease in circulating blood volume;
b) increase in the number of red blood cells;
c) decreased muscle strength;
d) decrease in maximum cardiac output.
24. What biological features of cabbage should be taken into account when growing it?
a) low need for water, nutrients, light;
b) greater need for water, nutrients, light, moderate temperature;
c) heat-loving, shade-tolerant, low need for nutrients;
d) rapid growth, short growing season.
13. Name a group of organisms whose number of representatives predominates over representatives of other groups that are part of grazing food chains (grazing).
a) producers;
b) first-order consumers;
c) second-order consumers;
d) third-order consumers.
14. Indicate the most complex terrestrial biogeocenosis.
a) birch grove;
b) pine forest;
c) oak forest;
d) river floodplain.
15. Name the environmental factor that is limiting for brook trout.
a) current speed;
b) temperature;
c) oxygen concentration;
d) illumination.
16. In mid-summer, the growth of perennial plants slows down or stops completely, and the number of flowering plants decreases. What factor and what change in it causes such phenomena?
a) decrease in temperature;
b) decrease;
c) decreasing day length;
d) decrease in the intensity of solar radiation.
17. Archaebacteria do not include:
a) halobacteria;
b) methanogens;
c) spirochetes;
d) thermoplasma.

18. The main signs of hominization are not:
a) upright posture;
b) adaptation to the work activity of the hand;
c) social behavior;
d) structure of the dental system.
19 Bacilli are:
a) gram-positive spore-forming rods;
b) gram-negative spore-forming rods;
c) gram-negative non-spore-forming rods;
d) gram-positive non-spore-forming rods.
20. When warm-bloodedness occurred, the morphological feature became decisive:
a) hair and feathers;
b) four-chamber heart;
c) alveolar structure of the lungs, increasing the intensity of gas exchange;
d) increased myoglobin content in muscles.