Properties and functions of cell organelles table. The structure of eukaryotic cells

The structure and functions of cell organelles.

Parts and organelles of the cell

Structural features

Functions performed

Plasma (cell) membrane.

Educated a double layer of lipid molecules (bilayer) and molecules proteins. The membrane is dominatedphospholipids . Proteins are immersed at different depths in the lipid layer or are located on the outer or inner surface of the membrane. Some proteins located on the outer surface are attachedcarbohydrates, which are a kind of indicators of cell type.Membrane proteins: enzymes; receptors; channel-forming proteins (transport of ions into and out of the cell).

Outside the membrane, plant cells havecell wall . Animal cells outside of the membrane are coveredglycocalyx - a thin layer of proteins and polysaccharides.

1 . barrier function (protects the cytoplasm from physical and chemical damage).

2 . Metabolism between the cytoplasm and the environment.

3. Transport of substances : water, ions, inorganic and organic molecules enter the cell from the external environment. Metabolic products and substances synthesized in the cell are released into the external environment. Passive transport (osmosis, diffusion), active transport (phagocytosis, pinocytosis, sodium-potassium pump). Plant cells cannot capture substances with the help of phagocytosis, because. on top of the membrane are covered with a dense layer of fiber.4 Receptor function - membrane receptor proteins transmit signals from the outside into the cell.

5 . Provides communication between cells.

Cytoplasm

The main substancehyaloplasm (thick, colorless colloidal solution): 70-90% water, plus proteins, lipids, and minerals.

In the cytoplasm (in eukaryotes) there is a complex support system -cytoskeleton. cytoskeleton consists of three elements:

- microtubules (protein tubulin)

- intermediate filaments

- microfilaments ( actin protein)

It is capable of movement - circular, striated, ciliary.

1 .In the hyaloplasm processes of metabolism in the cell proceed.

2 .Through it, the interaction of the nucleus and organelles occurs.

3 . Cytoskeleton:

- mechanical function (maintains the shape of the cell);

- transport (transfer of various substances, movement of organelles); -participation in the processes of phagocytosis and pinocytosis (microfilaments are able to change the shape of the membrane).

Core

1 .The nucleus stores hereditary information about all the features and properties of the cell and the organism as a whole.

2 . The nucleus regulates all metabolic and energy processes.

Nuclear envelope (karyolemma) consisting of two membranes with pores: the inner one is smooth, the outer one passes into the EPS channels.

1 . Separates the nucleus from the cytoplasm.

2 . Regulates the transport of substances from the nucleus to the cytoplasm (i-RNA, t-RNA, ribosomes) and from the cytoplasm to the nucleus (organic substances, ATP)

Nuclear sap, or karyoplasm (semi-liquid)

1 .Transport of substances

2 . The environment in which the nucleoli and chromatin are located.

Chromatin is DNA associated with proteins. Before cell division, DNA coils up to form chromosomes. Eachchromosome formed by one DNA molecule in complex with the main protein- histone.

DNA contains the genetic information of a cell.

Nucleoli- dense rounded bodies, consisting of protein and RNA. Nucleoli are formed in certain regions of the chromosomes.

Formation of halves (subunits) of ribosomes from rRNA and protein.

Ribosomes

(non-membrane organelles)

Consist of two subunits - large and small. Each subunit is a complex of rRNA with proteins.

Protein synthesis.

Cell Center (non-membrane organelle)

Comprises two centrioles - cylinders located perpendicular to each other.Centriole walls educated nine triplets of microtubules. The main protein that forms centrioles is tubulin.

1 . Participates in the formation of the cytoskeleton.

2 . It plays an important role in cell division (participates in the formation of fission spindle filaments).

Endoplasmic reticulum ER

(single-membrane organelle)

A) EPS rough (granular)

B) EPS is smooth

Formed by a system of connectedcavities, tubules, tubules.

Ribosomes are located on membranes.

The membranes are smooth (devoid of ribosomes)

transport system of the cell. Substances synthesized on the EPS membranes are transferred inside the tubules and transported through them to the Golgi apparatus.

Synthesis of proteins.

Synthesis of carbohydrates and lipids.

In liver cells, EPS is involved in the neutralization of toxic substances, and calcium ions, which are necessary for muscle contraction, accumulate in muscle cells.

Golgi complex (apparatus)

(single-membrane organelle)

Discovered in 1898 in neurons by the Italian histologist Camillo Golgi. Located next to the EPS. Consists of 3 main components:

- stacks flattened, slightly curved, disc-shapedcavities - "tanks"

System tubules, departing from the cavities;

- bubbles at the ends of the tubes.

1 .Substances that are used in the cell or are excreted into the external environment are accumulated.

2 . Formation of lysosomes.

3 . assembly of cell membranes.

Lysosomes (single-membrane organelles)

A small membranous vesicle containing digestiveenzymes(50 species).

1 .Cleavage (digestion) of polymeric organic compounds that have entered the animal cell during phagocytosis and pinocytosis to monomers absorbed by the cell.

2 . Participation in the removal of dying organs (tail in tadpoles), cells and organelles. During starvation, lysosomes dissolve some organelles without killing the cell.

Mitochondria (two-membrane organelles)

Spherical, oval or rod-shaped. Covered with outer and inner membranes.The outer membrane is smooth, while the inner forms numerous protrusions, folds -cristae . The inner membrane contains respiratory enzymes and ATP synthesis enzymes. The matrix contains a solution of various enzymes. They have their own genetic system that provides them self-reproduction: DNA, RNA, ribosomes, proteins, lipids, carbohydrates. They can synthesize proteins themselves.

Synthesis of ATP.

The energy of food substances is converted into the energy of ATP, which is necessary for the life of the cell and the organism as a whole.

plastids

(two-membrane organelles).

Characteristic only for plant cells To.

A) leukoplasts

leucoplasts → chloroplasts (in the light)

chloroplasts → chromoplasts.

B) Chromoplasts

The shape is round, colorless.

Spherical shape, contain red, yellow, orange pigments.

Serve as a place of accumulation of spare nutrients (starch grains).

They create a wide variety of colors of flowers (attracting pollinating insects) and plant fruits (spreading seeds by animals).

B) chloroplasts (colour green)

Biconvex lens shape.The outer membrane is smooth, the inner membrane is folded . Outgrowths are formed from its folds -thylakoids ( flat bags). Stacks of thylakoids -grains. Gran membranes contain chlorophyll (a green pigment). Each chloroplast contains about 50 grains. In the intervals between the grains in the matrix (stroma) - DNA, RNA, ribosomes. Thus,have their own genetic system, providing them self-reproduction. Synthesis of proteins by ribosomes.

Thanks to chlorophyll in chloroplasts, the energy of sunlight is converted into the chemical energy of ATP. ATP is used to synthesize organic compounds.

Photosynthesis is the process of formation of organic substances (glucose) from inorganic substances: carbon dioxide and water in the presence of light energy and chlorophyll pigment with the release of oxygen.

Organelles of movement

Eyelashes - numerous cytoplasmic outgrowths on the surface of the membrane.

Removal of dust particles (ciliated epithelium of the upper respiratory tract);

Movement (ciliates - shoe)

Flagella - single cytoplasmic outgrowths on the surface of the membrane.

Locomotion (spermatozoa, zoospores, unicellular organisms)

pseudopods - amoeboid protrusions of the cytoplasm.

They are formed in animals in different places of the cytoplasm to capture food, for movement.

myofibrils - thin filaments up to 1 cm long and more (actin and myosin)

Serve to reduce the muscle fibers along which they are located.

Vacuoles.

Only found in plant cells.

Cavities filled withcell sap - water with sugars and other organic and inorganic substances dissolved in it. Cell sap may contain pigments that give blue, purple, crimson color to petals and other parts of plants, as well as autumn leaves.

1. Maintenance of turgor pressure of cells.

2. Accumulation of reserve substances.

3. Coloring of plant organs (attraction of pollinating insects, distribution of fruits and seeds).

Cell structure. The main parts and organelles of the cell, their structure and functions.

A cell is an elementary unit of the structure and vital activity of all organisms, having its own metabolism, capable of independent existence, self-reproduction and development.
Cell organelles are permanent cellular structures, cellular organs that ensure the performance of specific functions in the process of cell life - the storage and transmission of genetic information, the transfer of substances, the synthesis and transformation of substances and energy, division, movement, etc.
Chromosomes are nucleoprotein structures in the nucleus of a eukaryotic cell, in which most of the hereditary information is concentrated and which are designed for its storage, implementation and transmission.

2. Name the main components of cells.
Cytoplasm, nucleus, plasma membrane, mitochondria, ribosomes, Golgi complex, endoplasmic reticulum, lysosomes, microtubules and microfilaments.

3. Give examples of nuclear-free cells. Explain the reason for their non-nuclear. What is the difference between the life of non-nuclear cells and cells with a nucleus?
Prokaryotes are cells of microorganisms that instead of a nucleus contain chromatin in the cell, which contains hereditary information.
In eukaryotes: mammalian erythrocytes. In place of the nucleus, they contain hemoglobin and, consequently, the binding of O2 and CO2 increases, the oxygen capacity of the blood - gas exchange in the lungs and tissues proceeds more efficiently.

4. Complete the diagram "Types of organelles by structure."

5. Fill in the table "Structure and functions of cell organelles".

7. What are cell inclusions? What is their purpose?
These are accumulations of substances that the cell either uses for its own needs or releases into the external environment. These can be protein granules, fat drops, starch or glycogen grains located directly in the cytoplasm.

eukaryotic and prokaryotic cells. The structure and functions of chromosomes.
1. Define the concepts.
Eukaryotes are organisms whose cells contain one or more nuclei.
Prokaryotes are organisms whose cells do not have a well-formed nucleus.
Aerobes are organisms that use oxygen in the air for energy.
Anaerobes are organisms that do not use oxygen for energy metabolism.

3. Fill in the table "Comparison of prokaryotic and eukaryotic cells."

4. Draw a schematic structure of the chromosomes of prokaryotic and eukaryotic cells. Sign their basic structures.
What do the chromosomes of eukaryotic and prokaryotic cells have in common and how do they differ?
In prokaryotes, DNA is circular, has no sheath, and is located right in the center of the cell. Sometimes bacteria don't have DNA, but instead have RNA.
In eukaryotes, DNA is linear, located in the chromosomes in the nucleus, covered with an additional shell.
What these cells have in common is that the genetic material is represented by DNA located in the center of the cell. The function is the same - the storage and transmission of hereditary information.

6. Why do scientists believe that prokaryotes are the most ancient organisms on our planet?
Prokaryotes are the simplest and most primitive organisms in structure and life, however, they easily adapt to almost any conditions. This allowed them to populate the planets and give rise to other, more advanced organisms.

2. Representatives of what kingdoms of wildlife consist of eukaryotic cells?
Fungi, plants and animals are eukaryotes.

As a rule, a eukaryotic cell has a single nucleus, but there are binuclear (ciliates) and multinuclear cells (opaline). Some highly specialized cells lose their nucleus for the second time (mammalian erythrocytes, angiosperm sieve tubes).
The shape of the nucleus is spherical, elliptical, less often lobed, bean-shaped, etc. The diameter of the nucleus is usually from 3 to 10 microns.

Core structure:

1 - outer membrane; 2 - inner membrane; 3 - pores; 4 - nucleolus; 5 - heterochromatin; 6 - euchromatin.

The nucleus is delimited from the cytoplasm by two membranes (each of them has a typical structure). Between the membranes is a narrow gap filled with a semi-liquid substance. In some places, the membranes merge with each other, forming pores (3), through which the exchange of substances between the nucleus and the cytoplasm takes place. The outer nuclear (1) membrane from the side facing the cytoplasm is covered with ribosomes, giving it a roughness, the inner (2) membrane is smooth. Nuclear membranes are part of the cell membrane system: outgrowths of the outer nuclear membrane are connected to the channels of the endoplasmic reticulum, forming a single system of communicating channels.

Karyoplasm (nuclear juice, nucleoplasm) - the inner contents of the nucleus, in which chromatin and one or more nucleoli are located. The composition of the nuclear juice includes various proteins (including nuclear enzymes), free nucleotides.

The nucleolus (4) is a rounded dense body immersed in nuclear juice. The number of nucleoli depends on the functional state of the nucleus and varies from 1 to 7 or more. Nucleoli are found only in non-dividing nuclei; during mitosis they disappear. The nucleolus is formed on certain regions of chromosomes that carry information about the structure of rRNA. Such regions are called the nucleolar organizer and contain numerous copies of the rRNA-coding genes. Ribosome subunits are formed from rRNA and proteins coming from the cytoplasm. Thus, the nucleolus is an accumulation of rRNA and ribosomal subunits at different stages of their formation.

Chromatin - internal nucleoprotein structures of the nucleus, stained with some dyes and differ in shape from the nucleolus. Chromatin has the form of lumps, granules and threads. The chemical composition of chromatin: 1) DNA (30–45%), 2) histone proteins (30–50%), 3) non-histone proteins (4–33%), therefore, chromatin is a deoxyribonucleoprotein complex (DNP). Depending on the functional state of chromatin, there are: heterochromatin (5) and euchromatin (6). Euchromatin - genetically active, heterochromatin - genetically inactive sections of chromatin. Euchromatin is not distinguishable under light microscopy, is weakly stained and represents decondensed (despiralized, untwisted) sections of chromatin. Under a light microscope, heterochromatin looks like clumps or granules, is intensely stained and is a condensed (spiralized, compacted) sections of chromatin. Chromatin is a form of existence of genetic material in interphase cells. During cell division (mitosis, meiosis), chromatin is converted into chromosomes.

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, come in different shapes and sizes, each variety performs a specific function, but the main features of their structure are similar.

First, let's find out what underlies structural organization of 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 protein molecules are immersed from the outside and inside.

What property is characteristic for 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 The 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 the main component, 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 an important structural feature of the organic compounds of a cell, then the answer can be given as follows.

• many of them contain carbon atoms that have different chemical and physical properties, and are also able to combine 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 of the 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.

An independent biosystem that has the basic properties of all living things. So, it can develop, multiply, move, adapt and change. In addition, metabolism, a specific structure, and orderliness of structures and functions are inherent in any cells.

The science that studies cells is cytology. Its subject is the structural units of multicellular animals and plants, unicellular organisms - bacteria, protozoa and algae, consisting of only one cell.

If we talk about the general organization of the structural units of living organisms, then they consist of a shell and a nucleus with a nucleolus. They also include cell organelles, cytoplasm. To date, a variety of research methods have been highly developed, but microscopy occupies a leading position, which allows you to study the structure of cells and explore its main structural elements.

What is an organoid?

Organelles (they are also called organelles) are the permanent constituent elements of any cell that make it complete and perform certain functions. These are the structures that are vital to sustaining its activities.

The organelles include the nucleus, lysosomes, the endoplasmic reticulum and the Golgi complex, vacuoles and vesicles, mitochondria, ribosomes, and the cell center (centrosome). This also includes structures that form the cytoskeleton of the cell (microtubules and microfilaments), melanosomes. Separately, it is necessary to single out the organelles of movement. These are cilia, flagella, myofibrils and pseudopods.

All these structures are interconnected and ensure the coordinated activity of cells. That is why the question: "What is an organoid?" - you can answer that this is a component that can be equated to an organ of a multicellular organism.

Classification of organelles

Cells differ in size and shape, as well as their functions, but at the same time they have a similar chemical structure and a single principle of organization. At the same time, the question of what an organoid is and what structures it is is quite debatable. For example, lysosomes or vacuoles are sometimes not referred to as cell organelles.

If we talk about the classification of these cell components, then non-membrane and membrane organelles are distinguished. Non-membrane - this is the cell center and ribosomes. Organelles of movement (microtubules and microfilaments) are also devoid of membranes.

The structure of membrane organelles is based on the presence of a biological membrane. Single-membrane and double-membrane organelles have a shell with a single structure, which consists of a double layer of phospholipids and protein molecules. It separates the cytoplasm from the external environment, helps the cell to maintain its shape. It is worth remembering that in addition to the membrane, there is also an outer cellulose membrane, which is called the cell wall. It performs a supporting function.

Membrane organelles include EPS, lysosomes and mitochondria, as well as lysosomes and plastids. Their membranes can differ only in the set of proteins.

If we talk about the functional ability of organelles, then some of them are able to synthesize certain substances. So, important organelles of synthesis are mitochondria, in which ATP is formed. Ribosomes, plastids (chloroplasts) and the rough endoplasmic reticulum are responsible for the synthesis of proteins, the smooth ER is responsible for the synthesis of lipids and carbohydrates.

Consider the structure and functions of organelles in more detail.

Core

This organelle is extremely important, because when it is removed, the cells cease to function and die.

The nucleus has a double membrane with many pores. With the help of them, it is closely associated with the endoplasmic reticulum and cytoplasm. This organelle contains chromatin - chromosomes, which are a complex of proteins and DNA. Given this, we can say that it is the nucleus that is the organelle that is responsible for maintaining the bulk of the genome.

The liquid part of the nucleus is called karyoplasm. It contains the products of vital activity of the structures of the nucleus. The densest zone is the nucleolus, which houses ribosomes, complex proteins and RNA, as well as phosphates of potassium, magnesium, zinc, iron and calcium. The nucleolus disappears before and forms again at the last stages of this process.

Endoplasmic reticulum (reticulum)

EPS is a single-membrane organelle. It occupies half the volume of the cell and consists of tubules and cisterns that are connected to each other, as well as to the cytoplasmic membrane and the outer shell of the nucleus. The membrane of this organoid has the same structure as the plasmalemma. This structure is integral and does not open into the cytoplasm.

The endoplasmic reticulum is smooth and granular (rough). Ribosomes are located on the inner shell of the granular ER, in which protein synthesis takes place. There are no ribosomes on the surface of the smooth endoplasmic reticulum, but carbohydrate and fat synthesis takes place here.

All substances that are formed in the endoplasmic reticulum are transported through the system of tubules and tubules to their destinations, where they accumulate and are subsequently used in various biochemical processes.

Given the synthesizing ability of EPS, the rough reticulum is located in cells whose main function is the formation of proteins, and the smooth reticulum is located in cells synthesizing carbohydrates and fats. In addition, calcium ions accumulate in the smooth reticulum, which are necessary for the normal functioning of cells or the body as a whole.

It should also be noted that the ER is the site of the formation of the Golgi apparatus.

Lysosomes, their functions

Lysosomes are cellular organelles that are represented by single-membrane round-shaped sacs with hydrolytic and digestive enzymes (proteases, lipases and nucleases). The content of lysosomes is characterized by an acidic environment. The membranes of these formations isolate them from the cytoplasm, preventing the destruction of other structural components of cells. When the enzymes of the lysosome are released into the cytoplasm, the cell self-destructs - autolysis.

It should be noted that enzymes are primarily synthesized on the rough endoplasmic reticulum, after which they move to the Golgi apparatus. Here they undergo modification, are packed into membrane vesicles and begin to separate, becoming independent components of the cell - lysosomes, which are primary and secondary.

Primary lysosomes are structures that separate from the Golgi apparatus, and secondary (digestive vacuoles) are those that form as a result of the fusion of primary lysosomes and endocytic vacuoles.

Given this structure and organization, the main functions of lysosomes can be distinguished:

• digestion of various substances inside the cell;
• destruction of cellular structures that are not needed;
• participation in the processes of cell reorganization.

Vacuoles

Vacuoles are single-membrane organelles of a spherical shape, which are reservoirs of water and organic and inorganic compounds dissolved in it. The Golgi apparatus and ER are involved in the formation of these structures.

There are few vacuoles in an animal cell. They are small and occupy no more than 5% of the volume. Their main role is to ensure the transport of substances throughout the cell.

Vacuoles are large and occupy up to 90% of the volume. In a mature cell, there is only one vacuole, which occupies a central position. Its membrane is called the tonoplast, and its contents are called cell sap. The main functions of plant vacuoles are to ensure the tension of the cell membrane, the accumulation of various compounds and waste products of the cell. In addition, these plant cell organelles supply the water needed for the photosynthesis process.

If we talk about the composition of cell sap, then it includes the following substances:

• spare - organic acids, carbohydrates and proteins, individual amino acids;
• compounds that are formed during the life of cells and accumulate in them (alkaloids, tannins and phenols);
• phytoncides and phytohormones;
• pigments, due to which the fruits, roots and flower petals are painted in the appropriate color.

Golgi complex

The structure of organoids called the "Golgi apparatus" is quite simple. In plant cells, they look like separate bodies with a membrane; in animal cells, they are represented by cisterns, tubules, and bladders. The structural unit of the Golgi complex is the dictyosome, which is represented by a stack of 4-6 "tanks" and small vesicles that are separated from them and are an intracellular transport system, and can also serve as a source of lysosomes. The number of dictyosomes can vary from one to several hundred.

The Golgi complex is usually located near the nucleus. In animal cells - near the cell center. The main functions of these organelles are as follows:

• secretion and accumulation of proteins, lipids and saccharides;
• modification of organic compounds entering the Golgi complex;
• This organelle is the site of lysosome formation.

It should be noted that ER, lysosomes, vacuoles, and the Golgi apparatus together form a tubular-vacuolar system that divides the cell into separate sections with corresponding functions. In addition, this system ensures constant renewal of the membranes.

Mitochondria are the powerhouses of the cell

Mitochondria are rod-shaped, spherical, or filamentous double-membrane organelles that synthesize ATP. They have a smooth outer surface and an inner membrane with numerous folds called cristae. It should be noted that the number of cristae in mitochondria may vary depending on the energy requirement of the cell. It is on the inner membrane that numerous enzyme complexes synthesizing adenosine triphosphate are concentrated. Here the energy of chemical bonds is converted into ATP. In addition, the breakdown of fatty acids and carbohydrates takes place in the mitochondria with the release of energy, which is accumulated and used for the processes of growth and synthesis.

The internal environment of these organelles is called the matrix. It contains circular DNA and RNA, small ribosomes. Interestingly, mitochondria are semi-autonomous organelles, since they depend on the functioning of the cell, but at the same time they can maintain a certain independence. So, they are able to synthesize their own proteins and enzymes, as well as reproduce on their own.

It is believed that mitochondria arose when aerobic prokaryotic organisms entered the host cell, which led to the formation of a specific symbiotic complex. Thus, mitochondrial DNA has the same structure as the DNA of modern bacteria, and protein synthesis in both mitochondria and bacteria is inhibited by the same antibiotics.

Plastids - plant cell organelles

Plastids are fairly large organelles. They are present only in plant cells and are formed from precursors - proplastids, contain DNA. These organelles play an important role in metabolism and are separated from the cytoplasm by a double membrane. In addition, they can form an ordered system of internal membranes.

Plastids are of three types:

Ribosomes

What is an organoid called called consisting of two fragments (small and large subunit). Their diameter is about 20 nm. They are found in cells of all types. These are organelles of animal and plant cells, bacteria. These structures are formed in the nucleus, after which they pass into the cytoplasm, where they are placed freely or attached to the EPS. Depending on the synthesizing properties, ribosomes function alone or combine into complexes, forming polyribosomes. In this case, these non-membrane organelles are bound by a messenger RNA molecule.

The ribosome contains 4 rRNA molecules that make up its backbone, as well as various proteins. The main task of this organoid is to assemble the polypeptide chain, which is the first step in protein synthesis. Those proteins that are formed by the ribosomes of the endoplasmic reticulum can be used by the whole organism. Proteins for the needs of an individual cell are synthesized by ribosomes, which are located in the cytoplasm. It should be noted that ribosomes are also found in mitochondria and plastids.

cell cytoskeleton

The cellular cytoskeleton is formed by microtubules and microfilaments. Microtubules are cylindrical formations with a diameter of 24 nm. Their length is 100 µm-1 mm. The main component is a protein called tubulin. It is incapable of contraction and can be destroyed by colchicine. Microtubules are located in the hyaloplasm and perform the following functions:

• create an elastic, but at the same time, a strong frame of the cell, which allows it to maintain its shape;
• take part in the process of distribution of cell chromosomes;
• provide movement of organelles;
• contained in the cell center, as well as in flagella and cilia.

Microfilaments are filaments that are placed under and consist of the protein actin or myosin. They can contract, resulting in movement of the cytoplasm or protrusion of the cell membrane. In addition, these components are involved in the formation of constriction during cell division.

Cell center (centrosome)

This organelle consists of 2 centrioles and a centrosphere. Cylindrical centriole. Its walls are formed by three microtubules, which merge with each other through cross-links. Centrioles are arranged in pairs at right angles to each other. It should be noted that the cells of higher plants lack these organelles.

The main role of the cell center is to ensure the uniform distribution of chromosomes during cell division. It is also the center of organization of the cytoskeleton.

Movement organelles

The organelles of movement include cilia, as well as flagella. These are tiny growths in the form of hairs. The flagellum contains 20 microtubules. Its base is located in the cytoplasm and is called the basal body. The length of the flagellum is 100 µm or more. Flagella that are only 10-20 microns in size are called cilia. When microtubules slide, cilia and flagella are able to oscillate, causing movement of the cell itself. The cytoplasm may contain contractile fibrils called myofibrils - these are organelles of an animal cell. Myofibrils, as a rule, are located in myocytes - muscle tissue cells, as well as in heart cells. They are made up of smaller fibers (protofibrils).

It should be noted that myofibril bundles consist of dark fibers - these are anisotropic disks, as well as light areas - these are isotropic disks. The structural unit of the myofibril is the sarcomere. This is the area between the anisotropic and isotropic disk, which has actin and myosin filaments. When they slide, the sarcomere contracts, which leads to the movement of the entire muscle fiber. This uses the energy of ATP and calcium ions.

With the help of flagella, protozoa and spermatozoa of animals move. Cilia are the organ of movement of the ciliates-shoes. In animals and humans, they cover the airways and help to get rid of small solid particles, such as dust. In addition, there are also pseudopods that provide amoeboid movement and are elements of many unicellular and animal cells (for example, leukocytes).

Most plants cannot move in space. Their movements consist in growth, leaf movements and changes in the flow of the cytoplasm of cells.

Conclusion

Despite all the diversity of cells, they all have a similar structure and organization. The structure and functions of organelles are characterized by identical properties, ensuring the normal functioning of both a single cell and the whole organism.

This pattern can be expressed as follows.

Table "Organoids of eukaryotic cells"

If we draw conclusions, then we can say that there are minor differences between the animal and plant cells. At the same time, the functional features and structure of organelles (the table above confirms this) has a general principle of organization. The cell functions as a harmonious and integral system. At the same time, the functions of organelles are interconnected and are aimed at optimal operation and maintenance of the cell's vital activity.