A cell is an elementary part of an organism, capable of independent existence, self-reproduction and development. The cell is the basis of the structure and life activity of all living organisms and plants. Cells can exist as independent organisms or as part of multicellular organisms (tissue cells). The term “Cell” was proposed by the English microscopist R. Hooke (1665). The cell is the subject of study of a special branch of biology - cytology. More systematic study of cells began in the nineteenth century. One of the largest scientific theories of that time was the Cell Theory, which asserted the unity of structure of all living nature. The study of all life at the cellular level is at the core of modern biological research. In the structure and functions of each cell, signs are found that are common to all cells, which reflects the unity of their origin from primary organic substances. The particular characteristics of various cells are the result of their specialization in the process of evolution. Thus, all cells regulate metabolism in the same way, double and use their hereditary material, receive and utilize energy. At the same time, different single-celled organisms (amoebas, slippers, ciliates, etc.) differ quite greatly in size, shape, and behavior. The cells of multicellular organisms differ no less sharply. Thus, a person has lymphoid cells - small (about 10 microns in diameter) round cells involved in immunological reactions, and nerve cells, some of which have processes more than a meter long; These cells carry out the main regulatory functions in the body.
Cell structure.
The cells of all organisms have a single structural plan, which clearly shows the commonality of all life processes. Each cell includes two inextricably linked parts: the cytoplasm and the nucleus. Both the cytoplasm and the nucleus are characterized by complexity and strictly ordered structure and, in turn, they include many different structural units that perform very specific functions. Shell. It directly interacts with the external environment and interacts with neighboring cells (in multicellular organisms). The shell is the custom of the cell. She vigilantly ensures that currently unnecessary substances do not penetrate into the cell; on the contrary, the substances that the cell needs can count on its maximum assistance. The core shell is double; consists of inner and outer nuclear membranes. Between these membranes is the perinuclear space. The outer nuclear membrane is usually associated with endoplasmic reticulum channels. The core shell contains numerous pores. They are formed by the closure of the outer and inner membranes and have different diameters. Some nuclei, such as egg nuclei, have many pores and are located at regular intervals on the surface of the nucleus. The number of pores in the nuclear envelope varies various types cells. The pores are located at an equal distance from each other. Since the diameter of the pore can vary, and in some cases its walls have a rather complex structure, it seems that the pores are contracting, or closing, or, conversely, expanding. Thanks to the pores, the karyoplasm comes into direct contact with the cytoplasm. Quite large molecules of nucleosides, nucleotides, amino acids and proteins easily pass through the pores, and thus an active exchange takes place between the cytoplasm and the nucleus.
Most living organisms have cellular structure. A cell is a structural and functional unit of living things. It is characterized by all the signs and functions of living organisms: metabolism and energy, growth, reproduction, self-regulation. Cells vary in shape, size, functions, and type of metabolism (Fig. 47).
Rice. 47. Diversity of cells: 1 - green euglena; 2 - bacteria; 3 - plant cell of the leaf pulp; 4 - epithelial cell; 5 - nerve cell
Cell sizes vary from 3-10 to 100 µm (1 µm = 0.001 m). Cells smaller than 1-3 microns in size are less common. 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, all cells have much in common. They have the same chemical composition and overall plan buildings.
Chemical composition cells. Of all the 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. From inorganic substances that are part of living organisms, highest value has water. 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, the cell also contains organic matter: 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, and regulation of all cell life processes.
Squirrels perform a number of functions: construction, regulatory, transport, contractile, protective, energy. But the most important is the enzymatic function of proteins.
Enzymes- these are biological catalysts that accelerate and regulate all the diversity chemical reactions occurring in living organisms. Not a single reaction in a living cell occurs without the participation of enzymes.
Lipids And carbohydrates They perform mainly construction and energy functions and are reserve nutrients for the body.
So, phospholipids together with proteins they build all membrane structures of the cell. A high molecular weight carbohydrate, cellulose forms the cell wall of plants and fungi.
Fats, starch And glycogen are reserve nutrients for the cell and the body as a whole. Glucose, fructose, sucrose and others Sahara are part of the roots, leaves, and fruits of plants. Glucose is an obligatory component of the blood plasma of humans and many animals. When carbohydrates and fats are broken down in the body, a large amount of energy is released, which is necessary for vital processes.
Cellular structures. The cell consists of an outer cell membrane, cytoplasm with organelles and a nucleus (Fig. 48).
Rice. 48. Combined diagram 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 cell structure, which 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. Cells of plant organisms and fungi, in addition to the membrane on the outside, also have a shell. This non-living 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.
IN cytoplasm, The semi-liquid contents of the cell contain all the organelles.
Endoplasmic reticulum penetrates the cytoplasm, providing communication between individual parts of the cell and 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 occurs in the cell.
Golgi apparatus ensures 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 the substances entering the cell. nutrients, providing intracellular digestion.
Mitochondria- These are semi-autonomous membrane structures of elongated shape. Their number in cells varies and increases as a result of division. Mitochondria are the energy stations of the cell. During the process of respiration, the final oxidation of substances with atmospheric oxygen occurs. In this case, the released energy is stored in ATP molecules, the synthesis of which occurs in these structures.
Chloroplasts, semi-autonomous membrane organelles, are 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 participates in the process of cell division. It consists of two centrioles and a centrosphere. During division, they form spindle threads and provide uniform distribution chromosomes in a cell.
Core- This is the center for regulating the life of the cell. The nucleus is separated from the cytoplasm by a 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, and ribosomes occurs. Often one or more dark round formations can be seen in the nucleus - these are nucleoli. Ribosomes are formed and accumulated here. In the nucleus, DNA molecules are not visible, as they are in the form of thin strands of chromatin. Before division, DNA spirals, 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 paired set of chromosomes is called diploid. Some cells and organisms contain a single, unpaired set called haploid.
Rice. 49. A - chromosome structure: 1 - centromere; 2 - chromosome arms; 3 - DNA molecules; 4 - sister chromatids; B - types of chromosomes: 1 - equal-armed; 2 - different shoulders; 3 - single-shoulder
The number of chromosomes for each type of organism is constant. Thus, in human cells there are 46 chromosomes (23 pairs), in wheat cells there are 28 (14 pairs), and in pigeons there are 80 (40 pairs). These organisms contain a diploid set of chromosomes. Some organisms, such as algae, mosses, and 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 Euglena green, Chlamydomonas, and some bacteria, and cilia are found in ciliates, the cells of the ciliated epithelium of animals.
| |
§ 43. Basic criteria for living things§ 45. Features of cell activity
Similar pages
Organisms of living nature mainly have a cellular structure. In this article we will tell you in more detail about the structural features and functioning of cells, and introduce them to their chemical composition and varieties.
Structural features
The cell is the unit of structure and vital activity of all living things on our planet. They can have different sizes (from 3 to 100 microns) and shapes (cylindrical, spherical, oval), perform various functions, and participate in all kinds of metabolic processes.
From common features chemical composition and structure can be identified.
The main elements of the chemical composition are carbon, oxygen, nitrogen and hydrogen. These macroelements make up the bulk of all components. Among inorganic substances, water and mineral salts, which are presented in the form of ions, are of particular importance. These include iron, iodine, potassium, calcium, phosphorus, chlorine, etc.
Rice. 1. Chemical composition.
Also constituent elements are organic substances: carbohydrates, proteins, nucleic acids, lipids. The following table will help you understand the functions of each of them:
TOP 1 articlewho are reading along with this
The structural elements of a cell are the cell membrane, nucleus and cytoplasm with organelles. Each of the constituent elements has its own characteristics and functions. For example:
- core contains the genetic code and regulates all processes occurring within the cellular organism;
- cell membrane protects against exposure environment, gives shape;
The cell membrane of plants is much denser than that of animals. This is possible due to the presence of cellulose in the composition.
- cytoplasm ensures the interconnection of all organelles within the cell.
Among the organelles in all cells one can find ribosomes, lysosomes, the Golgi apparatus, mitochondria, and the endoplasmic reticulum.
Rice. 2. Cell structure.
Plant and animal cells are different from each other. Thus, a plant organism has vacuoles and plastids, which animals do not have. And the animal body contains cell centrioles, which are involved in division processes.
Features of life
The main manifestations of cell life are metabolic processes and energy conversion.
The formation of organic substances, which is accompanied by energy consumption, is called assimilation.
The breakdown or breakdown of organic substances, which releases energy, is called dissimilation.
Rice. 3. Cell activity
The sun is the main source of energy on Earth. Plants under the influence sun rays produce ATP molecules. Adenosine triphosphate (ATP) is an organic substance that acts as a kind of battery in living organisms.
Photosynthesis, which occurs in plant cells, gives oxygen to the atmosphere. Thanks to it, breathing is possible, and therefore the existence of all life on the planet.
Inside plants, under the influence of the Sun, organic substances are formed, which are consumed by other species of living nature (fungi, animals, bacteria).
Thanks to plants, all living organisms are provided not only with oxygen, but also with nutrients.
What have we learned?
The cell, like all living organisms, has its own characteristics in structure and life. Every cellular organism has a shell, nucleus and cytoplasm with organelles. The chemical composition of all cells is the same. The main components are carbon, oxygen, hydrogen and nitrogen. The main manifestations of cell life are the processes of assimilation and dissimilation.
Test on the topic
Evaluation of the report
average rating: 4.2. Total ratings received: 100.
Hello guys, today I will give you a biology lesson, my name is Elena Vladimirovna, I ask you not to be shy and be active in the lesson, sit down.
Today in the lesson we will not only discover new knowledge, but also trace our emotional condition through color. Let's determine which colors from the palette we will take for today's lesson, and what they will mean to us. What color expresses you confidence, self-satisfaction, delight - red. What color expresses you good mood, goal achievement, activity – yellow. What color is it winding? sadness, melancholy, ennui, sadness – black gray.(write in advance on the board to sign only colors). Guys, at a certain stage of the lesson you need to color the water in the laboratory beakers with one of these colors, according to your mood . (the glasses are numbered 1, 2, 3.) Agreed? Fine.
During the classes.
Theoretical stage:
Guys, look at the slide, read it poem.
Billions of years ago(slide 1)
In the chaos of the Universe
A drop of life was born
Timidly and timidly.
At the dawn of the living universe
Everything around was alien and dangerous.
Tiny, fragile creature
We began to build a strong house for Life.
Life has dressed itself in a shell.
What's around? There is water - you can drink.
Clean air, the sun was hot.
And the baby decided: “We will live!”
And off we go. Now a living cell
It began to grow stronger, multiply, grow,
So that the once wild planet
Everything could bloom like gardens.
So what is the main idea this poem? Respectively,subject our lesson today“The cell is the basis of the structure and functioning of organisms” (slide 2) .
Guys, where are cells located in living nature? Are all living organisms made of cells? Look at the slide (slide 3) What living organisms do you see? Are they made of cells? What kingdoms can these living organisms belong to? (bacteria, fungi, plants and animals). (Slide 4) Tell me, do the cells of plants, animals, fungi and bacteria have a similar structure? (No) . So, what are we going to do in class today? What is the purpose of the lesson: prove the unity of the animal world by identifying the structural features of the cells of plants, animals, fungi and bacteria. (slide 5)
There are information sheets on your tables, take them in your hands. You see a table that will become an indispensable reminder for each of you during today’s lesson. The first, second and third columns of the table are completed, you need to familiarize yourself with them. Get started.
Guys,Let's consolidate our knowledge about cell organelles and their functions by completing the task on the board. (slide 7) If we compare a cell with a factory, then which organelles and parts of the cell can be given the following names :
energy station (mitochondrion), finished product warehouse (Golgi apparatus), waste processing plant (lysosome), assembly container (ribosome), information center (nucleus), photochemical laboratory (chloroplast), highway (EPS).
Guys, tell me, do you know what cells are called prokaryotic? (without a nucleus, for example, bacteria), and eukaryotic (with a nucleus, for example, plants, animals, fungi).
Well done. Guys, I suggest you take a little rest and go on a journey through the eukaryotic cell. So, in the background of the film.
Dynamic pause. At the center of a eukaryotic cell is the nucleus, ( Child's name) we can ask you to leave. Along with the nucleus, what other organelles are there in the cell? Let's correctly imagine that they are near the core. All organelles of the cell are placed in a transparent, semi-viscous liquid - the cytoplasm. Please leave ( Names of 4 guys.) Hold hands. The cytoplasm is in constant movement. Move in a circle. Cell organelles immersed in the cytoplasm form the internal contents of the cell. Protects the internal contents of the cell from external environment cytoplasmic membrane. Please come out Names of 5 guys.) Hold hands, make wave-like movements. The main function of the membrane is to selectively conduct substances into the cell and remove unnecessary substances from it. If they enter the cell useful material, then you need to raise your hands up, we do the same when we release substances from the cell. If unwanted substances want to penetrate into the cell, the membrane closes and presses against each other, blocking the entrance to the cell. We still have (names of 2 children) Come to us, you will wake up with substances, your task is to penetrate the cell. Guys, we're ready. TO cell membrane the necessary substances are suitable. The cell needs to get rid of substances it does not need. Unnecessary substances enter the cell. The necessary substances are released by the cell. Well done, take your seats.
So guys, we have shown with this exercise that the cell is single, integral, open system. All processes in a cell occur naturally; cell organelles exchange substances not only with each other, but also with the environment.
Guys, close your eyes, relax, remember everything that happened to you up to this point in the lesson. Take a brush and paint the water in the glass number 1 with the color that matches your mood.
Practical stage:
Guys, tell me, can we see the cage at any time? How can we see the structure of a cell? (microscope). Yes, in order to gain knowledge about the structure of cells of plants, fungi, animals and bacteria, we will perform laboratory work. Since there are four kingdoms of the living organisms in question, there are also four laboratories. Look at the very top line in the information sheets. Here everyone has a laboratory number written on them. Grab a pen and information sheet and take a seat in your lab.
On the tables you see step by step instructions how to do laboratory work. Look at her. Read the goal laboratory work. (read aloud one by one ). In order to identify the structural features of a particular cell, you need to distribute tasks in the group. One person from the group sets up a light microscope, then a clear image of the preparation, raise your hands who wants to do this work. And the second person prepares the drug according to the instructions and gives it to a neighbor in the group for examination under a microscope, who is interested. And the third group member will study the theory about the structure of the cells in question. And each group member needs to examine the drug being studied under a microscope. After completing the laboratory work, each group will tell us about the work done and draw conclusions. While doing lab work, mark on your information sheets with a plus or minus sign which organelles are included in the cell being studied. Get started.
The guys listen carefully to the groups speaking and at the same time fill out the corresponding columns of the table in the information sheets.
Group defense: The first participant tells what drug they prepared and with a pointer shows those parts in the cells (slide 8) which participant 2 will talk about when telling the theory. The 3rd participant pronounces the conclusion to the work, and the remaining 2 participants speak interactive whiteboard do tasks. Drag the required organelles to the cell.
Coloring glass No. 2.
Fastening: test on the control sheet. Grade.
Homework: To choose from:
1. Paragraph text
2. Compose a crossword puzzle on the topic “Plant and animal cell", "Bacterial cell", "Fungi, plants or animals?".
3. Make a model (application) of a cell. Assessment in assessment sheets
Reflection. Please drain the liquid from glasses No. 1 and No. 2 and see what color it turns out.
