Biology(from the Greek words bios - life, logos - teaching) is a science that studies living organisms and natural phenomena.

The subject of biology is the diversity of living organisms inhabiting the Earth.

properties of wildlife. All living organisms have a number of common features and properties that distinguish them from bodies of inanimate nature. These are structural features, metabolism, movement, growth, reproduction, irritability, self-regulation. Let us dwell on each of the listed properties of living matter.

Highly ordered structure. Living organisms are made up of chemical substances, which have a higher level of organization than inanimate substances. All organisms have a specific structural plan - cellular or non-cellular (viruses).

Metabolism and energy- this is a set of processes of respiration, nutrition, excretion, through which the body receives from the external environment the substances and energy it needs, transforms and accumulates them in its body and releases waste products into the environment.

Irritability is the body's response to changes environment helping him to adapt and survive in changing conditions. When pricked with a needle, a person withdraws his hand, and the hydra shrinks into a ball. The plants turn towards the light, and the amoeba moves away from the salt crystal.

Growth and development. Living organisms grow, increase in size, develop, change due to the intake of nutrients.

reproduction- the ability of a living being to reproduce itself. Reproduction is associated with the phenomenon of transmission of hereditary information and is the most hallmark alive. The life of any organism is limited, but as a result of reproduction, living matter is "immortal".

Motion. Organisms are capable of more or less active movement. This is one of the clear signs of life. Movement occurs both within the body and at the cell level.

Self-regulation. One of the most characteristic properties of living things is the constancy of the internal environment of the organism under changing external conditions. Body temperature, pressure, saturation with gases, concentration of substances, etc. are regulated. The phenomenon of self-regulation is carried out not only at the level of the whole organism, but also at the level of the cell. In addition, due to the activity of living organisms, self-regulation is also inherent in the biosphere as a whole. Self-regulation is associated with such properties of the living as heredity and variability.

Heredity- this is the ability to transfer the signs and properties of an organism from generation to generation in the process of reproduction.

Variability is the ability of an organism to change its characteristics when interacting with the environment.

As a result of heredity and variability, living organisms adapt, adapt to external conditions, which allows them to survive and leave offspring.

Most living organisms have a cellular structure. The cell is the structural and functional unit of the living. It is characterized by all the signs and functions of living organisms: metabolism and energy, growth, reproduction, self-regulation. Cells are different in shape, size, functions, type of metabolism (Fig. 47).

Rice. 47. Diversity of cells: 1 - green euglena; 2 - bacterium; 3 - plant cell of leaf pulp; 4 - epithelial cell; 5 - nerve cell

Cell sizes vary from 3-10 to 100 µm (1 µm = 0.001 m). Less common are cells smaller than 1–3 µm. There are also giant cells, the size of which reaches several centimeters. The shape of the cells is also very diverse: spherical, cylindrical, oval, spindle-shaped, stellate, etc. However, there is much in common between all cells. They have the same chemical composition and general structure plan.

The chemical composition of the cell. Of all known chemical elements about 20 are found in living organisms, and 4 of them: oxygen, carbon, hydrogen and nitrogen account for up to 95%. These elements are called biogenic elements. Of the inorganic substances that make up living organisms, water is the most important. Its content in the cell ranges from 60 to 98%. In addition to water, the cell also contains minerals, mainly in the form of ions. These are compounds of iron, iodine, chlorine, phosphorus, calcium, sodium, potassium, etc.

In addition to inorganic substances, organic substances are also present in the cell: proteins, lipids (fats), carbohydrates (sugars), nucleic acids (DNA, RNA). They make up the bulk of the cell. The most important organic substances are nucleic acids and proteins. Nucleic acids(DNA and RNA) are involved in the transmission of hereditary information, protein synthesis, regulation of all cell vital processes.

Squirrels perform a number of functions: building, regulatory, transport, contractile, protective, energy. But the most important is the enzymatic function of proteins.

Enzymes- These are biological catalysts that accelerate and regulate the whole variety of chemical reactions occurring in living organisms. Not a single reaction in a living cell proceeds without the participation of enzymes.

Lipids and carbohydrates perform mainly building and energy functions, are reserve nutrients of the body.

So, phospholipids Together with proteins, they build all the membrane structures of the cell. Cellulose is a high molecular weight carbohydrate that forms the cell wall of plants and fungi.

Fats, starch and glycogen are reserve nutrients for the cell and the organism as a whole. Glucose, fructose, sucrose and others Sahara are part of the roots and leaves, fruits of plants. Glucose is an essential component of the blood plasma of humans and many animals. When carbohydrates and fats are broken down in the body, a large number of energy needed for life processes.

Cell structures. The cell consists of an outer cell membrane, cytoplasm with organelles and nuclei (Fig. 48).

Rice. 48. Combined scheme of the structure of an animal (A) and plant (B) cell: 1 - shell; 2 - outer cell membrane 3 - core; 4 – chromatin; 5 - nucleolus; 6 - endoplasmic reticulum (smooth and granular); 7 - mitochondria; 8 - chloroplasts; 9 - Golgi apparatus; 10 - lysosome; 11 - cell center; 12 - ribosomes; 13 - vacuole; 14 – cytoplasm

outer cell membrane- This is a single-membrane cellular structure that limits the living contents of the cell of all organisms. Possessing selective permeability, it protects the cell, regulates the flow of substances and exchange with the external environment, and maintains a certain shape of the cell. The cells of plant organisms, fungi, in addition to the membrane on the outside, also have a shell. This inanimate cellular structure consists of cellulose in plants and chitin in fungi, gives strength to the cell, protects it, and is the "skeleton" of plants and fungi.

AT cytoplasm, semi-liquid contents of the cell, are all organelles.

Endoplasmic reticulum penetrates the cytoplasm, providing communication between individual parts of the cell and the transport of substances. There are smooth and granular EPS. The granular ER contains ribosomes.

Ribosomes- These are small mushroom-shaped bodies on which protein synthesis takes place in the cell.

golgi apparatus provides packaging and removal of synthesized substances from the cell. In addition, from its structures are formed lysosomes. These spherical bodies contain enzymes that break down nutrients entering the cell, allowing for intracellular digestion.

Mitochondria- These are semi-autonomous membrane structures of an oblong shape. Their number in cells is different and increases as a result of division. Mitochondria are the powerhouses of the cell. In the process of respiration, the final oxidation of substances with atmospheric oxygen occurs in them. In this case, the released energy is stored in ATP molecules, the synthesis of which occurs in these structures.

chloroplasts, semi-autonomous membrane organelles, characteristic only of plant cells. Chloroplasts are green in color due to the pigment chlorophyll, they provide the process of photosynthesis.

In addition to chloroplasts, plant cells also have vacuoles filled with cell sap.

Cell Center involved in the process of cell division. It consists of two centrioles and a centrosphere. During division, they form the fission spindle threads and ensure an even distribution of chromosomes in the cell.

Core is the center of regulation of cell activity. The nucleus is separated from the cytoplasm nuclear membrane which has pores. Inside it is filled with karyoplasm, which contains DNA molecules that ensure the transmission of hereditary information. Here the synthesis of DNA, RNA, ribosomes takes place. Often in the nucleus you can see one or more dark rounded formations - these are the nucleoli. Here, ribosomes are formed and accumulated. In the nucleus, DNA molecules are not visible, as they are in the form of thin filaments of chromatin. Before division, DNA spiralizes, thickens, forms complexes with protein and turns into clearly visible structures - chromosomes (Fig. 49). Usually the chromosomes in a cell are paired, identical in shape, size and hereditary information. Paired chromosomes are called homologous. A double set of chromosomes is called diploid. Some cells and organisms contain a single, unpaired set called haploid.

Rice. 49. A - the structure of the chromosome: 1 - centromere; 2 – chromosome arms; 3 - DNA molecules; 4 - sister chromatids B - types of chromosomes: 1 - equal-shouldered; 2 - multi-shouldered; 3 - single shoulder

The number of chromosomes for each type of organism is constant. Thus, there are 46 chromosomes (23 pairs) in human cells, 28 (14 pairs) in wheat cells, and 80 (40 pairs) in pigeon cells. These organisms contain a diploid set of chromosomes. Some organisms, such as algae, mosses, fungi, have a haploid set of chromosomes. Sex cells in all organisms are haploid.

In addition to those listed, some cells have specific organelles - cilia and flagella, providing movement mainly in unicellular organisms, but they are also present in some cells multicellular organisms. For example, flagella are found in green euglena, chlamydomonas, and some bacteria, and cilia in ciliates, ciliary epithelial cells of animals.

Metabolism and energy in the cell. The basis of cell life is metabolism and energy conversion. The set of chemical transformations occurring in a cell or organism, interconnected and accompanied by the transformation of energy, is called metabolism and energy.

The synthesis of organic substances, accompanied by the absorption of energy, is called assimilation or plastic exchange. The breakdown, splitting of organic substances, accompanied by the release of energy, is called dissimilation or energy exchange.

The main source of energy on Earth is the Sun. Plant cells with special structures in chloroplasts capture the energy of the Sun, converting it into the energy of chemical bonds of molecules of organic substances and ATP.

ATP(adenosine triphosphate) is an organic substance, a universal energy accumulator in biological systems. Solar energy is converted into the energy of chemical bonds of this substance and is spent on the synthesis of glucose, starch and other organic substances.

Atmospheric oxygen, however strange it may seem, by-product plant life process - photosynthesis.

The process of synthesizing organic substances from inorganic substances under the influence of solar energy is called photosynthesis.

The generalized photosynthesis equation can be represented as follows:

6CO 2 + 6H 2 O - light> C 6 H 12 O 6 + 6O 2.

In plants, organic substances are created in the process of primary synthesis from carbon dioxide, water and mineral salts. Animals, fungi, many bacteria use ready-made organic substances (from plants). In addition, photosynthesis produces oxygen, which is necessary for living organisms to breathe.

In the process of nutrition and respiration, organic substances are broken down and oxidized by oxygen. The released energy is partly released in the form of heat, and partly re-stored in the synthesized ATP molecules. This process takes place in the mitochondria. The end products of the breakdown of organic matter are water, carbon dioxide, ammonia compounds that are reused in the process of photosynthesis. The energy stored in ATP is spent on the secondary synthesis of organic substances characteristic of each organism, on growth, reproduction.

So, plants provide all organisms not only with nutrients, but also with oxygen. In addition, they convert the energy of the Sun and transmit it through organic matter to all other groups of organisms.

Metabolism as the main property of organisms. The body is in a complex relationship with the environment. From it he receives food, water, oxygen, light, heat. By creating a mass of living matter through these substances and energy, he builds his body. However, using this environment, the organism, due to its vital activity, simultaneously affects it, changes it. Consequently, the main process of the relationship between the organism and the environment is the exchange of substances and energy.

Types of metabolism. Environmental factors have different meanings for different organisms. Plants need light, water and carbon dioxide, minerals to grow and develop. Such conditions are insufficient for animals and fungi. They need organic nutrients. According to the method of nutrition, the source of obtaining organic substances and energy, all organisms are divided into autotrophic and heterotrophic.

Autotrophic organisms synthesize organic substances in the process of photosynthesis from inorganic (carbon dioxide, water, mineral salts), using the energy of sunlight. They include all plant organisms, photosynthetic cyanobacteria. Chemosynthetic bacteria are also capable of autotrophic nutrition, using the energy released during the oxidation of inorganic substances: sulfur, iron, nitrogen.

The process of autotrophic assimilation is carried out due to the energy of sunlight or the oxidation of inorganic substances, while organic substances are synthesized from inorganic substances. Depending on the absorption of inorganic matter, carbon assimilation, nitrogen assimilation, sulfur assimilation and others are distinguished. minerals. Autotrophic assimilation is associated with the processes of photosynthesis and chemosynthesis and is called primary synthesis of organic matter.

heterotrophic organisms receive ready-made organic substances from autotrophs. The source of energy for them is the energy stored in organic matter and released during chemical reactions breakdown and oxidation of these substances. These include animals, fungi, and many bacteria.

In heterotrophic assimilation, the body absorbs organic substances in finished form and converts them into its own organic substances due to the energy contained in the absorbed substances. Heterotrophic assimilation includes the processes of food consumption, digestion, assimilation and synthesis of new organic substances. This process is called secondary synthesis of organic substances.

The processes of dissimilation in organisms also differ. One of them needs oxygen to live. aerobic organisms. Others do not need oxygen, and their vital processes can proceed in an oxygen-free environment - this is anaerobic organisms.

Distinguish external respiration and internal. Gas exchange between the body and the external environment, which includes the absorption of oxygen and the release of carbon dioxide, as well as the transport of these substances through the body to individual organs, tissues and cells, is called external breath. In this process, oxygen is not used, but only transported.

internal, or cellular, respiration includes the biochemical processes that lead to the uptake of oxygen, the release of energy, and the formation of water and carbon dioxide. These processes take place in the cytoplasm and mitochondria of eukaryotic cells or on special membranes of prokaryotic cells.

The generalized equation of the breathing process:

C 6 H 12 O 6 + 6O 2 > 6CO 2 + 6H 2 O.

2. Another form of dissimilation is anaerobic, or oxygen-free, oxidation. The processes of energy metabolism in this case proceed according to the type of fermentation. Fermentation- this is a form of dissimilation in which energy-rich organic substances are split with the release of energy into less energy-rich, but also organic substances.

Depending on the final products, types of fermentation are distinguished: alcohol, lactic acid, acetic acid, etc. Alcoholic fermentation occurs in yeast fungi, some bacteria, and also occurs in some plant tissues. Lactic acid fermentation occurs in lactic acid bacteria, and also occurs in the muscle tissue of humans and animals with a lack of oxygen.

The relationship of metabolic reactions in autotrophic and heterotrophic organisms. Through metabolic processes, autotrophic and heterotrophic organisms are interconnected in nature (Fig. 50).

Rice. fifty. The flow of matter and energy in the biosphere

The most important groups of organisms are autotrophs, which are able to synthesize organic substances from inorganic ones. Most autotrophs are green plants that, during photosynthesis, convert inorganic carbon - carbon dioxide into complex organic compounds. Green plants also release oxygen during photosynthesis, which is necessary for the respiration of living beings.

Heterotrophs assimilate only ready-made organic substances, receiving energy from their breakdown. Autotrophic and heterotrophic organisms are interconnected by the processes of metabolism and energy. Photosynthesis is practically the only process that provides organisms with nutrients and oxygen.

Despite the large scale of photosynthesis, the green plants of the Earth use only 1% of the solar energy falling on the leaves. One of the most important tasks of biology is to increase the coefficient of use of solar energy by cultivated plants, the creation of productive varieties.

In recent years, the single-celled alga Chlorella, which contains up to 6% chlorophyll in its body and has a remarkable ability to absorb up to 20% of solar energy, has attracted special attention. With artificial breeding, chlorella multiplies rapidly, and the protein content in its cell increases. This protein is used as food additives in many foods. It has been established that up to 700 kg of dry matter of chlorella can be obtained daily from 1 ha of water surface. In addition, a large number of vitamins are synthesized in chlorella.

Another interest in chlorella is related to space travel. Chlorella under artificial conditions can provide the oxygen released during photosynthesis to a spacecraft.

The concept of irritability. Microorganisms, plants and animals respond to a wide variety of environmental influences: to mechanical influences (prick, pressure, impact, etc.), to changes in temperature, intensity and direction of light rays, to sound, electrical stimulation, changes in chemical composition air, water or soil, etc. This leads to certain fluctuations of the body between a stable and unstable state. Living organisms are able, to the extent of their development, to analyze these states and respond appropriately to them. Similar properties of all organisms are called irritability and excitability.

Irritability is the ability of an organism to respond to external or internal influences.

Irritability arose in living organisms as a device that provides better metabolism and protection from the effects of environmental conditions.

Excitability- this is the ability of living organisms to perceive the effects of stimuli and respond to them with an excitation reaction.

The impact of the environment affects the state of the cell and its organelles, tissues, organs and the body as a whole. The body responds to this with appropriate reactions.

The simplest manifestation of irritability is motion. It is characteristic of even the simplest organisms. This can be observed in an experiment on an amoeba under a microscope. If small lumps of food or sugar crystals are placed next to the amoeba, then it begins to actively move towards the nutrient. With the help of pseudopods, the amoeba envelops the lump, involving it inside the cell. There immediately formed digestive vacuole in which food is digested.

With the complication of the structure of the body, both metabolism and manifestations of irritability become more complicated. Single-celled organisms and plants do not special bodies providing perception and transmission of stimuli coming from the environment. Multicellular animals have sensory organs and a nervous system, thanks to which they perceive stimuli, and the responses to them achieve great accuracy and expediency.

Irritability in unicellular organisms. Taxi.

The simplest forms of irritability are observed in microorganisms (bacteria, unicellular fungi, algae, protozoa).

In the amoeba example, we observed the movement of the amoeba towards the stimulus (food). Such a motor reaction of unicellular organisms in response to irritation from the external environment is called taxis. Taxis is caused by chemical irritation, which is why it is also called chemotaxis(Fig. 51).

Rice. 51. Chemotaxis in ciliates

Taxis can be positive or negative. Place the test tube with the culture of ciliates-shoes in a closed cardboard box with a single hole located against the middle part of the tube, and expose it to light.

After a few hours, all ciliates will concentrate in the illuminated part of the tube. It's positive phototaxis.

Taxis are characteristic of multicellular animals. For example, blood leukocytes show positive chemotaxis in relation to substances secreted by bacteria, concentrate in the places of accumulation of these bacteria, capture and digest them.

Irritability in multicellular plants. Tropisms. Although multicellular plants do not have sensory organs and a nervous system, they nevertheless clearly manifest various forms irritability. They consist in changing the direction of growth of a plant or its organs (root, stem, leaves). Such manifestations of irritability in multicellular plants are called tropisms.

Stem with leaves exhibit positive phototropism and grow towards the light, and the root - negative phototropism(Fig. 52). Plants respond to the Earth's gravitational field. Pay attention to the trees growing on the side of the mountain. Although the soil surface is sloped, the trees grow vertically. The response of plants to gravity is called geotropism(Fig. 53). The root that emerges from a germinating seed is always directed downward towards the ground - positive geotropism. The shoot with leaves developing from the seed is always directed upwards from the ground - negative geotropism.

Tropisms are very diverse and play an important role in plant life. They are pronounced in the direction of growth in various climbing and climbing plants, such as grapes, hops.

Rice. 52. Phototropism

Rice. 53. Geotropism: 1 - a flower pot with straight-growing seedlings of radish; 2 - a flower pot, laid on its side and kept in the dark to eliminate phototropism; 3 - seedlings in a flower pot bent in the direction opposite to the action of gravity (stems have negative geotropism)

In addition to tropisms, other types of movements are observed in plants - nastia. They differ from tropisms in the absence of a specific orientation to the stimulus that caused them. For example, if you touch the leaves of a bashful mimosa, they quickly fold in the longitudinal direction and fall down. After some time, the leaves again take their previous position (Fig. 54).

Rice. 54. Nastia at bashful mimosa: 1 - in normal condition; 2 - when irritated

Flowers of many plants react to light and humidity. For example, in a tulip, the flowers open in the light, and close in the dark. In a dandelion, the inflorescence closes in cloudy weather and opens in clear weather.

Irritability in multicellular animals. Reflexes. In connection with the development in multicellular animals of the nervous system, sense organs and organs of movement, the forms of irritability become more complicated and depend on the close interaction of these organs.

In its simplest form, such irritation occurs already in the intestinal cavity. If pricked with a needle freshwater hydra, then it will shrink into a ball. External irritation is perceived by a sensitive cell. The excitation that has arisen in it is transmitted to the nerve cell. The nerve cell transmits excitation to the skin-muscle cell, which reacts to irritation with a contraction. This process is called reflex (reflection).

Reflex is the body's response to a stimulus nervous system.

The idea of ​​a reflex was expressed by Descartes. Later it was developed in the works of I. M. Sechenov, I. p. Pavlov.

The path traveled by nervous excitation from the organ that perceives the irritation to the organ that performs the response is called reflex arc.

In organisms with a nervous system, there are two types of reflexes: unconditioned (congenital) and conditioned (acquired). Conditioned reflexes formed on the basis of unconditional.

Any irritation causes a change in the metabolism in cells, which leads to the emergence of excitation and a response occurs.

The period of cell life in which all metabolic processes take place is called cell life cycle.

The cell cycle consists of interphase and division.

Interphase is the period between two cell divisions. It is characterized by active metabolic processes, protein and RNA synthesis, accumulation of nutrients by the cell, growth and increase in volume. By the end of interphase, DNA duplication (replication) occurs. As a result, each chromosome contains two DNA molecules and consists of two sister chromatids. The cell is ready to divide.

Cell division. The ability to divide is the most important property of cellular life. The mechanism of self-reproduction works already at the cellular level. The most common way of cell division is mitosis (Fig. 55).

Rice. 55. Interphase (A) and phases of mitosis (B): 1 - prophase; 2 - metaphase; 3 - anaphase; 4 - telophase

Mitosis- this is the process of formation of two daughter cells, identical to the original mother cell.

Mitosis consists of four successive phases, ensuring an even distribution genetic information and organelles between two daughter cells.

1. AT prophase the nuclear membrane disappears, the chromosomes spiralize as much as possible, become clearly visible. Each chromosome consists of two sister chromatids. The centrioles of the cell center diverge towards the poles and form a spindle of division.

2. AT metaphase chromosomes are located in the equatorial zone, the spindle fibers are connected to the centromeres of the chromosomes.

3. Anaphase characterized by the divergence of sister chromatids-chromosomes to the poles of the cell. Each pole has as many chromosomes as there were in the original cell.

4. AT telophase division of the cytoplasm and organelles occurs, a partition of the cell membrane is formed in the center of the cell and two new daughter cells appear.

The entire division process lasts from several minutes to 3 hours, depending on the cell type and the organism. The stage of cell division in time is several times shorter than its interphase. The biological meaning of mitosis is to ensure the constancy of the number of chromosomes and hereditary information, the complete identity of the original and newly emerging cells.

In nature, there are two types of reproduction of organisms: asexual and sexual.

asexual reproduction is the formation of a new organism from one cell or group of cells of the original parent organism. In this case, only one parent individual participates in reproduction, which transfers its hereditary information to child individuals.

Mitosis is the basis of asexual reproduction. There are several forms of asexual reproduction.

simple division, or division in two, characteristic of unicellular organisms. From one cell, two daughter cells are formed by mitosis, each of which becomes a new organism.

budding It is a form of asexual reproduction in which the offspring is separated from the parent. This form is typical for yeast, hydra and some other animals.

In spore plants (algae, mosses, ferns), reproduction occurs with the help of dispute, special cells formed in the mother's body. Each spore, germinating, gives rise to a new organism.

Vegetative reproduction is reproduction individual bodies, parts of organs or body. It is based on the ability of organisms to restore the missing parts of the body - regeneration. It occurs in plants (reproduction by stems, leaves, shoots), in lower invertebrates (coelenterates, flat and annelids).

sexual reproduction- this is the formation of a new organism with the participation of two parent individuals. The new organism carries hereditary information from both parents.

During sexual reproduction, the fusion of germ cells takes place. gametes male and female body. Sex cells are formed as a result of a special type of division. In this case, unlike the cells of an adult organism, which carry a diploid (double) set of chromosomes, the resulting gametes have a haploid (single) set. As a result of fertilization, the paired, diploid set of chromosomes is restored. One chromosome from a pair is paternal, and the other is maternal. Gametes are formed in the gonads or in specialized cells during meiosis.

Meiosis- this is a cell division in which the chromosome set of the cell is halved (Fig. 56). This division is called reduction.

Rice. 56. Phases of meiosis: A - first division; B - the second division. 1, 2 – prophase I; 3 - metaphase I; 4 - anaphase I; 5 – telophase I; 6 - prophase II; 7 - metaphase II; 8 - anaphase II; 9 - telophase II

Meiosis is characterized by the same stages as mitosis, but the process consists of two successive divisions (meiosis I and meiosis II). As a result, not two, but four cells are formed. The biological meaning of meiosis is to ensure the constancy of the number of chromosomes in newly formed organisms during fertilization. Women's sex cell – egg, always large, rich in nutrients, often immobile.

male reproductive cells spermatozoa, small, often mobile, have flagella, they are formed much more than eggs. In seed plants, the male gametes are non-motile and are called sperm.

Fertilization- the process of fusion of male and female germ cells, resulting in the formation of zygote.

The zygote develops into an embryo that gives rise to a new organism.

Fertilization is external and internal. external fertilization characteristic of water dwellers. Sex cells go into the external environment and merge outside the body (fish, amphibians, algae). Internal fertilization characteristic of terrestrial organisms. Fertilization occurs in the female genital organs. The embryo can develop both in the body of the maternal organism (mammals) and outside it - in the egg (birds, reptiles, insects).

The biological significance of fertilization lies in the fact that when the gametes merge, the diploid set of chromosomes is restored, and the new organism carries hereditary information and signs of two parents. This increases the variety of characteristics of organisms, increases their resilience.

The science that studies the structure and function of cells is called cytology.

Cell- an elementary structural and functional unit of the living.

Cells, despite their small size, are very complex. The internal semi-liquid content of the cell is called cytoplasm.

cell nucleus

The cell nucleus is the most important part of the cell.
The nucleus is separated from the cytoplasm by a membrane consisting of two membranes. There are numerous pores in the shell of the nucleus in order to various substances could pass from the cytoplasm to the nucleus, and vice versa.
The internal contents of the kernel are called karyoplasms or nuclear juice. located in the nuclear sap chromatin and nucleolus.
Chromatin is a strand of DNA. If the cell begins to divide, then the chromatin threads are tightly coiled around special proteins, like threads on a spool. Such dense formations are clearly visible under a microscope and are called chromosomes.

Core contains genetic information and controls the vital activity of the cell.

nucleolus is a dense rounded body inside the nucleus. Usually, there are from one to seven nucleoli in the cell nucleus. They are clearly visible between cell divisions, and during division they are destroyed.

The function of the nucleoli is the synthesis of RNA and proteins, from which special organelles are formed - ribosomes.
Ribosomes involved in protein synthesis. In the cytoplasm, ribosomes are most often located on rough endoplasmic reticulum. Less commonly, they are freely suspended in the cytoplasm of the cell.

Endoplasmic reticulum (ER) participates in the synthesis of cell proteins and the transport of substances within the cell.

A significant part of the substances synthesized by the cell (proteins, fats, carbohydrates) is not consumed immediately, but through the ER channels it enters for storage in special cavities, stacked in kind of stacks, “tanks”, and delimited from the cytoplasm by a membrane. These cavities are called apparatus (complex) Golgi. Most often, the tanks of the Golgi apparatus are located near the nucleus of the cell.
golgi apparatus takes part in the transformation of cell proteins and synthesizes lysosomes- digestive organelles of the cell.
Lysosomes are digestive enzymes, are “packed” into membrane vesicles, bud off and spread through the cytoplasm.
The Golgi complex also accumulates substances that the cell synthesizes for the needs of the whole organism and which are removed from the cell to the outside.

Mitochondria- energy organelles of cells. They convert nutrients into energy (ATP), participate in cell respiration.

Mitochondria are covered with two membranes: the outer membrane is smooth, and the inner one has numerous folds and protrusions - cristae.

plasma membrane

For the cell to be single system, it is necessary that all its parts (cytoplasm, nucleus, organelles) be held together. For this, in the process of evolution, plasma membrane, which, surrounding each cell, separates it from the external environment. The outer membrane protects the internal contents of the cell - the cytoplasm and nucleus - from damage, maintains a constant shape of the cell, provides communication between cells, selectively passes inside the cell necessary substances and removes metabolic products from the cell.

The structure of the membrane is the same in all cells. The basis of the membrane is a double layer of lipid molecules, in which numerous protein molecules are located. Some proteins are located on the surface of the lipid layer, others penetrate both layers of lipids through and through.

Special proteins form the thinnest channels through which potassium, sodium, calcium ions and some other ions with a small diameter can pass into or out of the cell. However, larger particles (nutrient molecules - proteins, carbohydrates, lipids) cannot pass through the membrane channels and enter the cell with the help of phagocytosis or pinocytosis:

• In the place where the food particle touches the outer membrane of the cell, an invagination is formed, and the particle enters the cell, surrounded by a membrane. This process is called phagocytosis (plant cells over the outer cell membrane are covered with a dense layer of fiber (cell membrane) and cannot capture substances by phagocytosis).
• pinocytosis differs from phagocytosis only in that in this case the invagination outer membrane captures not solid particles, but liquid droplets with substances dissolved in it. This is one of the main mechanisms for the penetration of substances into the cell.

Lesson development (lesson notes)

Presentations for lessons

Main general education

Line UMK VV Pasechnik. Biology (5-9)

Attention! The site administration site is not responsible for the content methodological developments, as well as for compliance with the development of the Federal State Educational Standard.

Winner of the competition "Electronic textbook in the classroom".

Target: generalize and systematize knowledge about the structure plant cell and the vital processes taking place in it.

Planned results:

• personal: the formation of communicative competence in communication with students and the teacher in the process of educational activities;
• meta-subject: the ability to correlate their actions with the planned results, control their activities, evaluate the results of activities;
• communicative: ability to work in a group;
• regulatory: the ability to make an assumption and prove it;
• cognitive: choose the grounds for comparison, building a logical chain
• subject: identifying the distinctive features of fungi, comparing biological objects, the ability to draw conclusions.

Type of lesson: summary lesson.

Lesson equipment: tables “Plant cell”, “Mitosis”, envelopes with assignments, microscopes, Petri dishes with pieces of onion, slides and coverslips, dissecting needles, pipettes, glasses of water, napkins. Tasks in envelopes.

EFU used in the lesson: electronic supplement to the textbook Biology. Bacteria, fungi, plants VV Pasechnik Drofa Publishing House.

Type of ICT tools used in the lesson: computer, projector, screen. laptop for teachers, laptops for students (20 pcs). Headphones (for working with sound sources of information). multimedia presentation.

The classroom is prepared for the work of students in three groups. Grouping occurs independently. Tokens of three colors according to the number of students. Students draw a token of a certain color and unite by color, forming three groups.

During the classes

organizational stage. Greetings

Formulation of the problem

W: After solving the puzzle, you will know the topic of the lesson.

COP PRO NZV VLT BSO ICR LAE YUDN GHI TNE

Knowledge update

At: The cell is the structural and functional unit of all living organisms. In addition, the cell itself is alive. All living organisms are either one free-living cell, or an association of a certain number of cells. Slide #2

?: What properties do all living organisms have?

O: Nutrition, respiration, excretion, growth and development, metabolism and energy, etc.

At: The cell is actually a self-replicating chemical system. It is physically separated from its environment, but it has the ability to exchange with this environment, that is, it is able to absorb substances that it needs as “food” and bring out the accumulated “waste”. Cells can reproduce by dividing.

?: Set a goal for the lesson

O: Repeat, consolidate the knowledge gained in the study of the topic: “ Cell structure organisms."

W: What questions should we repeat?

O: The structure of the cell, the processes of life in the cell.

Main stage. Generalization and systematization

At: You are divided into three groups. Choose a captain in your group. Captains are invited to receive envelopes with assignments. Preparation lasts for 7 minutes.

Student activities: within each group, roles are assigned to complete the task and protect their project. They study the material, analyze the information, make notes in notebooks. Prepare a group work report.

• I group"Structure of the plant cell". Using the information of the electronic textbook and using the interactive mode, create a “portrait of a cell” (interactive content, p. 36; Fig. 20 “Structure of a plant cell”).

1. Systematize knowledge about the structure and function of organelles; for this, move the mouse over the name of each of the elements of its structure and click the mouse.
2. Prepare a micropreparation of the skin of onion scales and examine it under a microscope. Slide #3

• II group“The device of a microscope and the rules for working with it” (interactive content, p. 32-33; Fig. 17 “Light microscope”).

1. Drag and drop the names of the elements of the structure of the light microscope with the mouse.
2. Drag with the mouse the magnification that gives the corresponding combination “Lens - eyepiece”. Slide #4

• III group“The vital activity of the cell. Cell division and growth” (interactive content p. 44; Fig. 24 “Interaction of neighboring cells”).

1. Using the interactive mode, generalize knowledge about the significance of the movement of the cytoplasm in the cell.
2. Using interactive mode, generalize knowledge about cell division. Slide #5

Each group, completing the task, uses different sources of information: an electronic supplement to the textbook, text and drawings of the textbook, a presentation for the lesson. Forms: frontal, group, individual. Methods: verbal (story, conversation); visual (demonstration of tables and slides); practical (search for information from different sources, mini-project); deductive (analysis, generalization). At the end of the work, students present the results of the work of the group.

After answering the questions, students receive other assignments. The teacher offers the most active students to move to another table. They get a more difficult task - to read the text, title it and insert the missing words (in the text they are now in italics).

Tasks of increased difficulty

Fill in the missing terms:

... is a structural and functional unit of all living organisms. All cells are separated from each other by a cell .... On outside, which contains a special dense shell, consisting of .... .The living contents of the cell are represented by .... - a colorless viscous translucent substance. Numerous are located in the cytoplasm .... The most important organelle of the cell is .... It stores hereditary information, regulates metabolic processes within the cell. The nucleus contains one or more ... . There are three types of plant cells... ... are green, ... red, and ... white. In old cells, cavities containing cell sap are clearly visible. These entities are called... .

Correct answer:Cell - the structural and functional unit of all living organisms. All cells cells are separated from each other shell. On the outer side, which is a special dense shell, consisting of fiber. The living content of the cell is represented cytoplasm – colorless viscous translucent substance. The cytoplasm contains numerous organelles. The most important organelle of the cell is core. It stores hereditary information, regulates metabolic processes within the cell. The nucleus contains one or more nucleoli. There are three types in the plant cell plastid. Chloroplasts are green in color chromoplasts red, and leucoplasts - white. In old cells, cavities containing cell sap are clearly visible. These formations are called vacuoles).

The rest of the students draw general scheme cell structure, marking all its parts, using colored pencils.

W: Unfortunately, cells, like all living things, die. Our bodies are also made up of cells. Tobacco smoking and alcohol consumption are especially destructive to the cells of the body.

Tobacco smoke contains toxic substances, such as nicotine, benzopyrene, which destroy cells and promote the development of malignant tumors.

Summarizing

Today we have repeated with you the features of the structure and vital activity of a plant cell. What conclusion can be drawn at the end of our lesson? Slide #6

O: A cell is an elementary living system, the basis of the structure and life of all living organisms. Despite the great diversity of plant and animal cells, all cells have the same parts of the cell membrane, cytoplasm and nucleus. In all cells, similar life processes take place: nutrition, respiration, growth, development, reproduction, metabolism. Slide number 7

Students come up with tokens and get grades.

Homework of the student's choice:

• Create a plant cell model using different materials (plasticine, colored paper, etc.)
• Write a story about the life of a plant cell
• Prepare a message about the discovery of R. Hooke
• Visit the school laboratory and prepare R. Hooke's "historical" preparation*

Used Books:

• A.A. Kalinina. Pourochnye developments in biology. 6 (7) class. - M .: Wako, 2005.

All living beings and organisms do not consist of cells: plants, fungi, bacteria, animals, people. Despite the minimum size, all the functions of the whole organism are performed by the cell. Complex processes take place inside it, on which the viability of the body and the work of its organs depend.

In contact with

Structural Features

Scientists are studying structural features of the cell and principles of its work. It is possible to examine in detail the features of the cell structure only with the help of a powerful microscope.

All our tissues - skin, bones, internal organs are made up of cells that are construction material, there are different forms and size, each variety performs a specific function, but the main features of their structure are similar.

First, let's find out what underlies structural organization cells. In the course of the research, scientists have found that the cellular foundation is membrane principle. It turns out that all cells are formed from membranes, which consist of a double layer of phospholipids, where from the outside and inside immersed protein molecules.

What property is characteristic of all types of cells: the same structure, as well as functionality - regulation of the metabolic process, the use of one's own genetic material (the presence and RNA), the production and consumption of energy.

At the basis of the structural organization of the cell, the following elements are distinguished that perform a specific function:

• membrane — cell wall is made up of fats and proteins. Its main task is to separate the substances inside from the external environment. The structure is semi-permeable: it is able to pass carbon monoxide;
• core- the central region and main component, is separated from other elements by a membrane. It is inside the nucleus that information about growth and development is located, the genetic material, presented in the form of DNA molecules that make up;
• cytoplasm- this is a liquid substance that forms an internal environment where various vital processes take place, contains a lot of important components.

What does the cellular content consist of, what are the functions of the cytoplasm and its main components:

1. Ribosome- the most important organelle, which is necessary for the processes of protein biosynthesis from amino acids, proteins perform a huge number of vital tasks.
2. Mitochondria- another component located inside the cytoplasm. It can be described in one phrase - an energy source. Their function is to provide the components with power for further energy production.
3. golgi apparatus consists of 5 - 8 pouches, which are interconnected. The main task of this apparatus is the transfer of proteins to other parts of the cell to provide energy potential.
4. Cleaning of damaged elements is carried out lysosomes.
5. Is engaged in transportation endoplasmic reticulum, through which proteins move molecules of useful substances.
6. Centrioles responsible for reproduction.

Core

Since it is a cellular center, therefore, special attention should be paid to its structure and functions. This component is an essential element for all cells: it contains hereditary traits. Without the nucleus, the processes of reproduction and transmission of genetic information would become impossible. Look at the picture depicting the structure of the nucleus.

• The nuclear membrane, which is highlighted in lilac, lets in the necessary substances and releases them back through the pores - small holes.
• Plasma is a viscous substance, it contains all the other nuclear components.
• the core is located in the very center, has the shape of a sphere. Its main function is the formation of new ribosomes.
• If you look at the central part of the cell in a section, you can see subtle blue weaves - chromatin, the main substance that consists of a complex of proteins and long strands of DNA that carry the necessary information.

cell membrane

Let's take a closer look at the work, structure and functions of this component. Below is a table that clearly shows the importance of the outer shell.

Chloroplasts

This is another very important component. But why was the chloroplast not mentioned earlier, you ask. Yes, because this component is found only in plant cells. The main difference between animals and plants lies in the mode of nutrition: in animals it is heterotrophic, while in plants it is autotrophic. This means that animals are not able to create, that is, synthesize organic substances from inorganic ones - they feed on ready-made organic substances. Plants, on the contrary, are capable of carrying out the process of photosynthesis and contain special components - chloroplasts. These are green plastids containing chlorophyll. With its participation, the energy of light is converted into the energy of chemical bonds of organic substances.

Interesting! Chloroplasts are concentrated in large volumes mainly in the aerial parts of plants - green fruits and leaves.

If you are asked a question: name important feature structure of organic compounds of the cell, the answer can be given as follows.

• many of them contain carbon atoms, which have different chemical and physical properties, and are also able to connect with each other;
• are carriers, active participants in various processes occurring in organisms, or are their products. This refers to hormones, various enzymes, vitamins;
• can form chains and rings, which provides a variety of connections;
• are destroyed by heating and interaction with oxygen;
• atoms in the composition of molecules combine with each other using covalent bonds, do not decompose into ions and therefore interact slowly, reactions between substances take a very long time - for several hours and even days.

The structure of the chloroplast

fabrics

Cells can exist one at a time, as in unicellular organisms, but most often they are combined into groups of their own kind and form various tissue structures that make up the body. There are several types of tissues in the human body:

• epithelial- focused on the surface skin, organs, elements of the digestive tract and respiratory system;
• muscular- we move thanks to the contraction of the muscles of our body, we carry out a variety of movements: from the simplest movement of the little finger to high-speed running. By the way, the heartbeat also occurs due to the contraction of muscle tissue;
• connective tissue makes up to 80 percent of the mass of all organs and plays a protective and supporting role;
• nervous- forms nerve fibers. Thanks to it, various impulses pass through the body.

reproduction process

Throughout the life of an organism, mitosis occurs - this is the name for the process of division, consisting of four stages:

1. Prophase. The two centrioles of the cell divide and move in opposite directions. At the same time, the chromosomes form pairs, and the shell of the nucleus begins to break down.
2. The second stage is called metaphase. Chromosomes are located between the centrioles, gradually the outer shell of the nucleus completely disappears.
3. Anaphase is the third stage, during which the movement of centrioles continues in the opposite direction from each other, and individual chromosomes also follow the centrioles and move away from each other. The cytoplasm and the whole cell begin to shrink.
4. Telophase- the final stage. The cytoplasm shrinks until two identical new cells appear. A new membrane is formed around the chromosomes and one pair of centrioles appears in each new cell.

Interesting! Cells in the epithelium divide faster than in bone tissue. It all depends on the density of the fabrics and other characteristics. The average life expectancy of the main structural units is 10 days.

Cell structure. The structure and functions of the cell. Cell life.

Conclusion

You learned what the structure of the cell is the most important component of the body. Billions of cells make up an amazingly wisely organized system that ensures the efficiency and vitality of all representatives of the animal and plant world.

The cell is the basic structural and functional unit of all living organisms, except for viruses. It has a specific structure, including many components that perform certain functions.

What science studies the cell?

Everyone knows that the science of living organisms is biology. The structure of the cell is studied by its branch - cytology.

What is a cell made of?

This structure consists of a membrane, cytoplasm, organelles, or organelles, and a nucleus (in prokaryotic cells is absent). The structure of the cells of organisms belonging to different classes is slightly different. Significant differences are observed between the structure of eukaryotic and prokaryotic cells.

plasma membrane

The membrane plays very important role- it separates and protects the contents of the cell from the external environment. It consists of three layers: two protein and medium phospholipid.

cell wall

Another structure that protects the cell from exposure external factors, located on top plasma membrane. It is present in the cells of plants, bacteria and fungi. In the first, it consists of cellulose, in the second, of murein, in the third, of chitin. In animal cells, a glycocalyx is located on top of the membrane, which consists of glycoproteins and polysaccharides.

Cytoplasm

It represents the entire space of the cell, bounded by the membrane, with the exception of the nucleus. The cytoplasm includes organelles that perform the main functions responsible for the life of the cell.

Organelles and their functions

The structure of a cell of a living organism implies a number of structures, each of which performs a specific function. They are called organelles, or organelles.

Mitochondria

They can be called one of the most important organelles. Mitochondria are responsible for the synthesis of energy necessary for life. In addition, they are involved in the synthesis of certain hormones and amino acids.

Energy in the mitochondria is produced due to the oxidation of ATP molecules, which occurs with the help of a special enzyme called ATP synthase. Mitochondria are round or rod-shaped structures. Their number in animal cage, on average, is 150-1500 pieces (it depends on its purpose). They consist of two membranes and a matrix, a semi-liquid mass that fills the interior of the organelle. The main component of the shells are proteins, and phospholipids are also present in their structure. The space between the membranes is filled with liquid. Within the mitochondrial matrix are grains that store certain substances, such as magnesium and calcium ions needed for energy production, and polysaccharides. Also, these organelles have their own protein biosynthesis apparatus, similar to that of prokaryotes. It consists of mitochondrial DNA, a set of enzymes, ribosomes, and RNA. The structure of a prokaryotic cell has its own characteristics: there are no mitochondria in it.

Ribosomes

These organelles are composed of ribosomal RNA (rRNA) and proteins. Thanks to them, translation is carried out - the process of protein synthesis on the mRNA matrix (messenger RNA). One cell can contain up to ten thousand of these organelles. Ribosomes consist of two parts: small and large, which unite directly in the presence of mRNA.

Ribosomes, which are involved in the synthesis of proteins necessary for the cell itself, are concentrated in the cytoplasm. And those with the help of which proteins are produced that are transported outside the cell are located on the plasma membrane.

Golgi complex

It is present only in eukaryotic cells. This organelle consists of dictosomes, which usually number about 20, but can reach up to several hundred. The Golgi apparatus enters into the structure of the cell only eukaryotic organisms. It is located near the nucleus and performs the function of synthesizing and storing certain substances, for example, polysaccharides. Lysosomes are formed in it, which will be discussed below. Also, this organelle is part of the excretory system of the cell. Dictosomes are presented in the form of stacks of flattened disk-shaped cisterns. Bubbles form at the edges of these structures, where substances are located that must be removed from the cell.

Lysosomes

These organelles are small vesicles with a set of enzymes. Their structure has a single membrane topped with a layer of protein. The function that lysosomes perform is the intracellular digestion of substances. Thanks to the hydrolase enzyme, fats, proteins, carbohydrates, and nucleic acids are broken down with the help of these organelles.

Endoplasmic reticulum (reticulum)

The structure of the cell of all eukaryotic cells implies the presence of EPS (endoplasmic reticulum). The endoplasmic reticulum consists of tubules and flattened cavities that have a membrane. This organoid is of two types: rough and smooth network. The first differs in that ribosomes are attached to its membrane, the second does not have such a feature. The rough endoplasmic reticulum performs the function of synthesizing proteins and lipids that are required for cell membrane formation or for other purposes. Smooth takes part in the production of fats, carbohydrates, hormones and other substances, except for proteins. Also, the endoplasmic reticulum performs the function of transporting substances through the cell.

cytoskeleton

It consists of microtubules and microfilaments (actin and intermediate). The components of the cytoskeleton are polymers of proteins, mainly actin, tubulin, or keratin. Microtubules serve to maintain the shape of the cell, they form the organs of movement in the simplest organisms, such as ciliates, chlamydomonas, euglena, etc. Actin microfilaments also play the role of a scaffold. In addition, they are involved in the process of moving organelles. Intermediate in different cells built from various proteins. They maintain the shape of the cell and also fix the nucleus and other organelles in a permanent position.

Cell Center

Consists of centrioles, which are shaped like a hollow cylinder. Its walls are made up of microtubules. This structure is involved in the division process, ensuring the distribution of chromosomes between daughter cells.

Core

In eukaryotic cells, it is one of the most important organelles. It stores DNA, which encodes information about the whole organism, about its properties, about proteins that must be synthesized by the cell, etc. It consists of a shell that protects the genetic material, nuclear juice (matrix), chromatin and nucleolus. The shell is formed from two porous membranes located at some distance from each other. The matrix is ​​represented by proteins; it forms a favorable environment inside the nucleus for storing hereditary information. The nuclear sap contains filamentous proteins that serve as a support, as well as RNA. Chromatin is also present here - the interphase form of the existence of chromosomes. During cell division, it turns from lumps into rod-shaped structures.

nucleolus

This is a separate part of the nucleus responsible for the formation of ribosomal RNA.

Organelles found only in plant cells

Plant cells have some organelles that are no longer characteristic of any organisms. These include vacuoles and plastids.

Vacuole

This is a kind of reservoir where reserve nutrients are stored, as well as waste products that cannot be brought out due to dense cell wall. It is separated from the cytoplasm by a specific membrane called the tonoplast. As the cell functions, individual small vacuoles merge into one large one - the central one.

plastids

These organelles are divided into three groups: chloroplasts, leukoplasts, and chromoplasts.

Chloroplasts

These are the most important organelles of the plant cell. Thanks to them, photosynthesis is carried out, during which the cell receives the nutrients it needs. Chloroplasts have two membranes: outer and inner; matrix - a substance that fills the inner space; own DNA and ribosomes; grains of starch; grains. The latter consist of stacks of thylakoids with chlorophyll surrounded by a membrane. It is in them that the process of photosynthesis takes place.

Leucoplasts

These structures consist of two membranes, a matrix, DNA, ribosomes, and thylakoids, but the latter do not contain chlorophyll. Leucoplasts perform a reserve function, accumulating nutrients. They contain special enzymes that make it possible to obtain starch from glucose, which, in fact, serves as a reserve substance.

Chromoplasts

These organelles have the same structure as those described above, however, they do not contain thylakoids, but there are carotenoids that have a specific color and are located directly near the membrane. It is thanks to these structures that the flower petals are colored in a certain color, which allows them to attract pollinating insects.