What organelles make up an animal cell? The structure of an animal cell. main organelles and their functions. What organelles make up the cell?

Organelles (organelles) of a cell are permanent parts of the cell that have a specific structure and perform specific functions. There are membrane and non-membrane organelles. TO membrane organelles include the cytoplasmic reticulum (endoplasmic reticulum), lamellar complex (Golgi apparatus), mitochondria, lysosomes, peroxisomes. Non-membrane organelles represented by ribosomes (polyribosomes), the cell center and cytoskeletal elements: microtubules and fibrillar structures.

Rice. 8.Diagram of the ultramicroscopic structure of a cell:

1 – granular endoplasmic reticulum, on the membranes of which attached ribosomes are located; 2 – agranular endoplasmic reticulum; 3 – Golgi complex; 4 – mitochondria; 5 – developing phagosome; 6 – primary lysosome (storage granule); 7 – phagolysosome; 8 – endocytic vesicles; 9 – secondary lysosome; 10 – residual body; 11 – peroxisome; 12 – microtubules; 13 - microfilaments; 14 – centrioles; 15 – free ribosomes; 16 – transport bubbles; 17 – exocytotic vesicle; 18 – fatty inclusions (lipid drop); 19 - glycogen inclusions; 20 – karyolemma (nuclear membrane); 21 – nuclear pores; 22 – nucleolus; 23 – heterochromatin; 24 – euchromatin; 25 – basal body of the cilium; 26 - eyelash; 27 – special intercellular contact (desmosome); 28 – gap intercellular contact

2.5.2.1. Membrane organelles (organelles)

The endoplasmic reticulum (endoplasmic reticulum, cytoplasmic reticulum) is a set of interconnected tubules, vacuoles and “cisterns”, the wall of which is formed by elementary biological membranes. Opened by K.R. Porter in 1945. The discovery and description of the endoplasmic reticulum (ER) is due to the introduction of the electron microscope into the practice of cytological studies. The membranes that form the EPS differ from the plasmalemma of the cell in their smaller thickness (5-7 nm) and higher concentration of proteins, primarily those with enzymatic activity . There are two types of EPS(Fig. 8): rough (granular) and smooth (agranular). Rough XPS It is represented by flattened cisterns, on the surface of which ribosomes and polysomes are located. The membranes of granular ER contain proteins that promote the binding of ribosomes and flattening of the cisterns. The rough ER is especially well developed in cells specialized in protein synthesis. The smooth ER is formed by intertwining tubules, tubes and small vesicles. The channels and tanks of the EPS of these two types are not differentiated: membranes of one type pass into membranes of another type, forming the so-calledtransitional (transient) EPS.

Mainfunctions of granular EPS are:

1) synthesis of proteins on attached ribosomes(secreted proteins, proteins of cell membranes and specific proteins of the contents of membrane organelles); 2) hydroxylation, sulfation, phosphorylation and glycosylation of proteins; 3) transport of substances within the cytoplasm; 4) accumulation of both synthesized and transported substances; 5) regulation biochemical reactions, associated with the orderly localization in the structures of EPS of substances that enter into reactions, as well as their catalysts - enzymes.

Smooth XPS It is distinguished by the absence of proteins (ribophorins) on the membranes that bind ribosomal subunits. It is assumed that smooth ER is formed as a result of the formation of outgrowths of rough ER, the membrane of which loses ribosomes.

Functions of smooth EPS are: 1) lipid synthesis, including membrane lipids; 2) synthesis of carbohydrates(glycogen, etc.); 3) cholesterol synthesis; 4) neutralization of toxic substances endogenous and exogenous origin; 5) accumulation of Ca ions 2+ ; 6) restoration of the karyolemma in telophase of mitosis; 7) transport of substances; 8) accumulation of substances.

As a rule, smooth ER is less developed in cells than rough ER, but it is much better developed in cells that produce steroids, triglycerides and cholesterol, as well as in liver cells that detoxify various substances.

Rice. 9. Golgi complex:

1 – stack of flattened tanks; 2 – bubbles; 3 – secretory vesicles (vacuoles)

Transitional (transient) EPS - this is the site of transition of granular ER into agranular ER, which is located at the forming surface of the Golgi complex. The tubes and tubules of the transitional ER disintegrate into fragments, from which vesicles are formed that transport material from the ER to the Golgi complex.

The lamellar complex (Golgi complex, Golgi apparatus) is a cell organelle involved in the final formation of its metabolic products.(secrets, collagen, glycogen, lipids and other products),as well as in the synthesis of glycoproteins. The organoid is named after the Italian histologist C. Golgi, who described it in 1898. Formed by three components(Fig. 9): 1) a stack of flattened tanks (sacs); 2) bubbles; 3) secretory vesicles (vacuoles). The zone of accumulation of these elements is called dictyosomes. There may be several such zones in a cell (sometimes several dozen or even hundreds). The Golgi complex is located near the cell nucleus, often near the centrioles, and less often scattered throughout the cytoplasm. In secretory cells, it is located in the apical part of the cell, through which secretion is released by exocytosis. From 3 to 30 cisterns in the form of curved disks with a diameter of 0.5-5 microns form a stack. Adjacent tanks are separated by spaces of 15-30 nm. Individual groups The cisterns within the dictyosome are distinguished by a special composition of enzymes that determine the nature of biochemical reactions, in particular protein processing, etc.

The second constituent element of the dictyosome is vesicles They are spherical formations with a diameter of 40-80 nm, the moderately dense contents of which are surrounded by a membrane. Bubbles are formed by splitting off from the tanks.

The third element of the dictyosome is secretory vesicles (vacuoles) They are relatively large (0.1-1.0 μm) spherical membrane formations containing a secretion of moderate density that undergoes condensation and compaction (condensation vacuoles).

The Golgi complex is clearly vertically polarized. It contains two surfaces (two poles):

1) cis-surface, or an immature surface that has a convex shape, faces the endoplasmic reticulum (nucleus) and is associated with small transport vesicles separating from it;

2) trans-surface, or the surface facing the concave plasmolemma (Fig. 8), on the side of which vacuoles (secretory granules) are separated from the cisterns of the Golgi complex.

Mainfunctions of the Golgi complex are: 1) synthesis of glycoproteins and polysaccharides; 2) modification of the primary secretion, its condensation and packaging into membrane vesicles (formation of secretory granules); 3) molecular processing(phosphorylation, sulfation, acylation, etc.); 4) accumulation of substances secreted by the cell; 5) formation of lysosomes; 6) sorting of proteins synthesized by the cell at the trans-surface before their final transport (produced through receptor proteins that recognize the signal regions of macromolecules and direct them to various vesicles); 7) transport of substances: From transport vesicles, substances penetrate into the stack of cisterns of the Golgi complex from the cis surface, and exit it in the form of vacuoles from the trans surface. The mechanism of transport is explained by two models: a) a model for the movement of vesicles budding from the previous cistern and merging with the subsequent cistern sequentially in the direction from the cis surface to the trans surface; b) a model of cisternae movement, based on the idea of ​​continuous new formation of cisternae due to the fusion of vesicles on the cis surface and subsequent disintegration into vacuoles of cisternae moving toward the trans surface.

The above main functions allow us to state that the lamellar complex is the most important organelle of the eukaryotic cell, ensuring the organization and integration of intracellular metabolism. In this organelle, the final stages of formation, maturation, sorting and packaging of all products secreted by the cell, lysosome enzymes, as well as proteins and glycoproteins of the cell surface apparatus and other substances take place.

Organelles of intracellular digestion. Lysosomes are small vesicles bounded by an elementary membrane containing hydrolytic enzymes. The lysosome membrane, about 6 nm thick, performs passive compartmentalization, temporarily separating hydrolytic enzymes (more than 30 varieties) from the hyaloplasm. In an intact state, the membrane is resistant to the action of hydrolytic enzymes and prevents their leakage into the hyaloplasm. Corticosteroid hormones play an important role in membrane stabilization. Damage to lysosome membranes leads to self-digestion of the cell by hydrolytic enzymes.

The lysosome membrane contains an ATP-dependent proton pump, ensuring acidification of the environment inside the lysosomes. The latter promotes the activation of lysosome enzymes - acid hydrolases. Along with the the lysosome membrane contains receptors that determine the binding of lysosomes to transport vesicles and phagosomes. The membrane also ensures the diffusion of substances from lysosomes into the hyaloplasm. The binding of some hydrolase molecules to the lysosome membrane leads to their inactivation.

There are several types of lysosomes:primary lysosomes (hydrolase vesicles), secondary lysosomes (phagolysosomes, or digestive vacuoles), endosomes, phagosomes, autophagolysosomes, residual bodies(Fig. 8).

Endosomes are membrane vesicles that transport macromolecules from the cell surface to lysosomes by endocytosis. During the transfer process, the contents of endosomes may not change or undergo partial cleavage. In the latter case, hydrolases penetrate into the endosomes or the endosomes directly merge with hydrolase vesicles, as a result of which the medium gradually becomes acidified. Endosomes are divided into two groups: early (peripheral) And late (perinuclear) endosomes.

Early (peripheral) endosomes are formed on early stages endocytosis after separation of vesicles with captured contents from the plasmalemma. They are located in the peripheral layers of the cytoplasm and characterized by a neutral or slightly alkaline environment. In them, ligands are separated from receptors, ligands are sorted, and, possibly, receptors are returned in special vesicles to the plasmalemma. Along with the in early endosomes, cleavage of com-

Rice. 10 (A). Scheme of the formation of lysosomes and their participation in intracellular digestion.(B)Electron micrograph of a section of secondary lysosomes (indicated by arrows):

1 – formation of small vesicles with enzymes from the granular endoplasmic reticulum; 2 – transfer of enzymes to the Golgi apparatus; 3 – formation of primary lysosomes; 4 – isolation and use of (5) hydrolases during extracellular cleavage; 6 - phagosomes; 7 – fusion of primary lysosomes with phagosomes; 8, 9 – formation of secondary lysosomes (phagolysosomes); 10 – excretion of residual bodies; 11 – fusion of primary lysosomes with collapsing cell structures; 12 – autophagolysosome

complexes “receptor-hormone”, “antigen-antibody”, limited cleavage of antigens, inactivation of individual molecules. Under acidic conditions (pH=6.0) the environment in early endosomes, partial breakdown of macromolecules may occur. Gradually, moving deeper into the cytoplasm, early endosomes turn into late (perinuclear) endosomes located in the deep layers of the cytoplasm, surrounding the core. They reach 0.6-0.8 microns in diameter and differ from early endosomes in their more acidic (pH = 5.5) contents and a higher level of enzymatic digestion of the contents.

Phagosomes (heterophagosomes) are membrane vesicles that contain material captured by the cell from outside, subject to intracellular digestion.

Primary lysosomes (hydrolase vesicles) - vesicles with a diameter of 0.2-0.5 microns containing inactive enzymes (Fig. 10). Their movement in the cytoplasm is controlled by microtubules. Hydrolase vesicles transport hydrolytic enzymes from the lamellar complex to the organelles of the endocytic pathway (phagosomes, endosomes, etc.).

Secondary lysosomes (phagolysosomes, digestive vacuoles) are vesicles in which intracellular digestion is actively carried out through hydrolases at pH≤5. Their diameter reaches 0.5-2 microns. Secondary lysosomes (phagolysosomes and autophagolysosomes) formed by fusion of a phagosome with an endosome or primary lysosome (phagolysosome) or by fusion of an autophagosome(membrane vesicle containing the cell's own components) with primary lysosome(Fig. 10) or late endosome (autophagolysosome). Autophagy ensures the digestion of areas of the cytoplasm, mitochondria, ribosomes, membrane fragments, etc. The loss of the latter in the cell is compensated by their new formation, which leads to renewal (“rejuvenation”) of cellular structures. So, in nerve cells In humans, functioning for many decades, most organelles are renewed within 1 month.

A type of lysosome containing undigested substances (structures) is called residual bodies. The latter can remain in the cytoplasm for a long time or release their contents through exocytosis outside the cell.(Fig. 10). A common type of residual bodies in the body of animals are lipofuscin granules, which are membrane vesicles (0.3-3 µm) containing the sparingly soluble brown pigment lipofuscin.

Peroxisomes are membrane vesicles with a diameter of up to 1.5 µm, the matrix of which contains about 15 enzymes(Fig. 8). Among the latter, the most important catalase, which accounts for up to 40% of the total protein of the organelle, as well as peroxidase, amino acid oxidase, etc. Peroxisomes are formed in the endoplasmic reticulum and are renewed every 5-6 days. Along with mitochondria, peroxisomes are an important center for oxygen utilization in the cell. In particular, under the influence of catalase, hydrogen peroxide (H 2 O 2), formed during the oxidation of amino acids, carbohydrates and other cellular substances, breaks down. Thus, peroxisomes protect the cell from the damaging effects of hydrogen peroxide.

Organelles of energy metabolism. Mitochondria first described by R. Kölliker in 1850 in the muscles of insects called sarcosomes. They were later studied and described by R. Altman in 1894 as "bioplasts", and in 1897 by K. Benda called them mitochondria. Mitochondria are membrane-bound organelles that provide the cell (organism) with energy. The source of energy stored in the form of phosphate bonds of ATP is oxidation processes. Along with the mitochondria are involved in the biosynthesis of steroids and nucleic acids, as well as in the oxidation fatty acids.

M

Rice. eleven. Mitochondria structure diagram:

1 – outer membrane; 2 – internal membrane; 3 – cristae; 4 – matrix

N

Rice. 12. Electron photograph of mitochondria (cross section)

The intermembrane space of mitochondria, 10-20 nm wide, contains no a large number of enzymes. It is limited from the inside by the inner mitochondrial membrane, which contains transport proteins, respiratory chain enzymes and succinate dehydrogenase, as well as an ATP synthetase complex. The inner membrane is characterized by low permeability to small ions. It forms folds 20 nm thick, which are most often located perpendicular to the longitudinal axis of mitochondria, and in some cases (muscle and other cells) - longitudinally. With increasing mitochondrial activity, the number of folds (their total area) increases. On the cristae areoxisomes - mushroom-shaped formations consisting of a rounded head with a diameter of 9 nm and a stalk 3 nm thick. ATP synthesis occurs in the head region. The processes of oxidation and ATP synthesis in mitochondria are separated, which is why not all the energy is accumulated in ATP, being partially dissipated in the form of heat. This separation is most pronounced, for example, in brown adipose tissue, which is used for the spring “warm-up” of animals that were in a state of “hibernation.”

The inner chamber of the mitochondrion (the area between the inner membrane and the cristae) is filledmatrix (Fig. 11, 12), containing Krebs cycle enzymes, protein synthesis enzymes, fatty acid oxidation enzymes, mitochondrial DNA, ribosomes and mitochondrial granules.

Mitochondrial DNA represents the mitochondria's own genetic apparatus. It has the appearance of a circular double-stranded molecule, which contains about 37 genes. Mitochondrial DNA differs from nuclear DNA in its low content of non-coding sequences and the absence of connections with histones. Mitochondrial DNA encodes mRNA, tRNA and rRNA, but provides the synthesis of only 5-6% of mitochondrial proteins(enzymes of the ion transport system and some enzymes of ATP synthesis). The synthesis of all other proteins, as well as the duplication of mitochondria, is controlled by nuclear DNA. Most of the mitochondrial ribosomal proteins are synthesized in the cytoplasm and then transported to the mitochondria. Inheritance of mitochondrial DNA in many species of eukaryotes, including humans, occurs only through the maternal line: the paternal mitochondrial DNA disappears during gametogenesis and fertilization.

Mitochondria have a relatively short life cycle (about 10 days). Their destruction occurs through autophagy, and new formation occurs through division (ligation) preceding mitochondria. The latter is preceded by mitochondrial DNA replication, which occurs independently of nuclear DNA replication at any phase of the cell cycle.

Prokaryotes do not have mitochondria, and their functions are performed by the cell membrane. According to one hypothesis, mitochondria originated from aerobic bacteria as a result of symbiogenesis. There is an assumption about the participation of mitochondria in the transmission of hereditary information.

Anyone knows from school that all living organisms, both plants and animals, consist of cells. But what they themselves consist of is not known to everyone, and even if it is known, it is not always good. In this article we will look at the structure of plant and animal cells, and understand their differences and similarities.

But first, let's figure out what an organoid is.

An organoid is an organ of a cell that performs some of its own individual functions in it, while ensuring its viability, because, without exception, every process occurring in the system is very important for this system. And all the organelles make up the system. Organelles are also called organelles.

Plant organelles

So, let's look at what organelles are found in plants and what exact functions they perform.

The nucleus (nuclear apparatus) is one of the most important organelles. It is responsible for the transmission of hereditary information - DNA (deoxyribonucleic acid). The nucleus is a round organelle. It has something like a skeleton - the nuclear matrix. It is the matrix that is responsible for the morphology of the nucleus, its shape and size. The nucleus contains nuclear sap, or karyoplasm. It is a fairly viscous, thick liquid in which there is a small nucleolus that forms proteins and DNA, as well as chromatin, which realizes the accumulated genetic material.

The nuclear apparatus itself, together with other organelles, is located in the cytoplasm - a liquid medium. The cytoplasm consists of proteins, carbohydrates, nucleic acids and other substances that are the results of the production of other organelles. Main function cytoplasm - transfer of substances between organelles to support life. Since the cytoplasm is a liquid, slight movement of organelles occurs inside the cell.

Membrane shell

The membrane membrane, or plasmalemma, performs protective function, protecting the organelles from any damage. The membrane shell is a film. It is not continuous - the shell has pores through which some substances enter the cytoplasm and others exit. Folds and outgrowths of the membrane provide a strong connection between cells. Shell protected cell wall, this is the exoskeleton that gives the cell special form.

Vacuoles

Vacuoles are special reservoirs for storing cell sap. It contains nutrients and waste products. Vacuoles accumulate it throughout the life of the cell; such reserves are necessary in case of damage (rarely) or lack of nutrients.

Apparatus, lysosomes and mitochondria

Chloroplasts, leucoplasts and chromoplasts

Plastids are double-membrane cell organelles, divided into three types - chloroplasts, leucoplasts and chromoplasts:

• Chloroplasts give plants green color, they have a round shape and contain a special substance - the pigment chlorophyll, which is involved in the process of photosynthesis.
• Leukoplasts are transparent organelles responsible for processing glucose into starch.
• Chromoplasts are plastids that are red, orange, or yellow color. They can develop from chloroplasts when they lose chlorophyll and starch. We can observe this process when leaves turn yellow or fruits ripen. Chromoplasts can transform back into chloroplasts under certain conditions.

Endoplasmic reticulum

The endoplasmic reticulum consists of ribosomes and polyribosomes. Ribosomes are synthesized in the nucleolus; they perform the function of protein biosynthesis. Ribosomal complexes consist of two parts - large and small. The number of ribosomes in the cytoplasmic space is predominant.

A polyribosome is a set of ribosomes that translate one large molecule of a substance.

Animal cell organelles

Some of the organelles completely coincide with plant organelles, and some plant organelles are not found in animals at all. Below is a table comparing the structural features.

Let's deal with the last two:

We can say that the structure of animal and plant cells is different because plants and animals have various shapes life. Thus, the organelles of a plant cell are better protected because plants are motionless - they cannot run away from danger. Plastids are present in the plant cell, providing the plant with another type of nutrition - photosynthesis. Animals, due to their characteristics, have absolutely no need for nutrition through the processing of sunlight. And therefore none of three types There cannot be plastids in an animal cell.

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-1.jpg" alt=">Structure and functions of cell organelles.">!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-2.jpg" alt=">Organoids are permanent cellular structures that have a certain structure, chemical composition and performing specific functions.">!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-3.jpg" alt=">Cytoplasmic inclusions are optional components of the cell that appear and disappear depending on on intensity"> Включения цитоплазмы - это необязательные компоненты клетки, появляющиеся и исчезающие в зависимости от интенсивности и характера обмена веществ в клетке и от условий существования организма. Включения имеют вид зерен, глыбок, капель, вакуолей, гранул различной величины и формы. Их химическая природа очень разнообразна. В зависимости от функционального назначения включения объединяют в группы. ГРУППЫ: ТРОФИЧЕСКИЕ ЭКСКРЕТЫ И ДР. СЕКРЕТЫ СПЕЦИАЛЬНЫЕ ВКЛЮЧЕНИЯ (ГЕМОГЛОБИН) ИНКРЕТЫ ПИГМЕНТЫ!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-4.jpg" alt=">Plant cell">!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-5.jpg" alt=">The role of the nucleus in the life of the cell Between the nucleus and the surrounding cytoplasm there is a constant exchange"> Роль ядра в жизни клетки Между ядром и окружающей его цитоплазмой происходит постоянный обмен веществ. Это хорошо видно на примере взаимодействия ДНК и РНК ядра и цитоплазмы. Ядро играет огромную роль в жизни клетки. Его роль очень велика не только процессах созидания живой материи, но и во всех других проявлениях жизнедеятельности клетки.!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-6.jpg" alt=">Animal cell">!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-7.jpg" alt=">Comparison">!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-8.jpg" alt=">Cell organelles">!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-9.jpg" alt="> Cell organoids General organoids Special purpose organoids"> Органоиды клетки Органоиды общего Специальные назначения органоиды Характерные для специализированных клеток Присутствующие во многоклеточного всех клетках эукариот организма или клеток одноклеточного организма Пластиды, митохондрии, Реснички, жгутики и т. д. лизосомы и т. д.!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-10.jpg" alt="> Classification of organelles Organelles Non-membrane Membrane"> Классификация органоидов Органоиды Немембранные Мембранные Рибосомы Одномембранные Двухмембранные Клеточный центр Микротрубочки ЭПС Митохондрии Микрофиламенты Комплекс пластиды Хромосомы Гольджи Лизосомы Вакуоли!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-12.jpg" alt="> No nucleic acids. Metabolism"> Нуклеиновых кислот нет. Метаболизм липидов Синтез белка на ШЭР!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-13.jpg" alt=">ER (endoplasmic reticulum) is a continuous three-dimensional network of tubules and cisterns. Begins as a protrusion of the outer"> ЭПС (эндоплазматическая сеть) - непрерывная трехмерная сеть канальцев и цистерн. Начинается как выпячивание внешней мембраны ядра и заканчивается у цитоплазматической мембраны. Различают гладкий и шероховатый ретикулум. На шероховатом находятся рибосомы. Это место синтеза большинства белков и липидов клетки. Гладкий используется для перемещения синтезированных веществ.!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-14.jpg" alt=">Participates in the accumulation of products synthesized in the endoplasmic reticulum in their chemical perestroika and"> Участвует в накоплении продуктов, синтезированных в эндоплазматической сети, в их химической перестройке и созревании. В цистернах комплекса Гольджи происходит синтез полисахаридов, их комплексирование с белковыми молекулами. Одна из главных функций комплекса Гольджи - формирование готовых секреторных продуктов, которые выводятся за пределы клетки путем экзоцитоза. Важнейшими для клетки функциями комплекса Гольджи также являются обновление клеточных мембран, в том числе и участков плазмолеммы, а также замещение дефектов плазмолеммы в процессе секреторной деятельности клетки. Комплекс Гольджи считается источником образования первичных лизосом, хотя их ферменты синтезируются и в гранулярной сети.!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-15.jpg" alt=">Mitochondria Mitochondria is a symbiotic organism. Its predecessor was"> Митохондрии Митохондрия - симбиотический организм. Предшественницей была бактерия. Имеется собственные ДНК, рибосомы, двойная мембрана. Внутренняя мембрана имеет большое количество впячиваний - крист. Осуществляет процесс дыхания в клетке. Синтезирует АТФ из АДФ и обеспечивает таким образом клетку энергией.!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-16.jpg" alt=">Lysosomes A lysosome is a small body limited from the cytoplasm by a single membrane. In it contains lytic"> Лизосомы Лизосома - небольшое тельце, ограниченное от цитоплазмы одинарной мембраной. В ней находятся литические ферменты, способные расщепить все биополимеры. Основная функция - автолиз - то есть расщепление отдельных органоидов, участков цитоплазмы клетки.!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-17.jpg" alt=">Peroxisomes Peroxisomes or microbodies. Round in shape. Contain one"> Пероксисомы Пероксисомы- или микротельца. Округлой формы. Содержат одну мембрану, не содержат ДНК и рибосом. Утилизируют кислород в клетке. (кислород очень вреден для клетки. Кислородом отбеливают)!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-18.jpg" alt=">Ribosomes are the smallest organelles. Found in the ER, cytoplasm, chloroplasts, mitochondria. They synthesize proteins,"> Рибосомы - мельчайшие органоиды. Находятся в ЭПР, цитоплазме, хлоропластах, митохондриях. Синтезируют белки, необходимые клетке, отдельным органоидам. К мембранам эндоплазматической сети прикреплено большое число рибосом - мельчайших органоидов клетки, имеющих вид сферы с диаметром 20 нм и состоящих из РНК и белка. На рибосомах и происходит синтез белков. Затем вновь синтезированные белки поступают в систему полостей и канальцев, по которым перемещаются внутри клетки. В цитоплазме клетки есть и свободные, не прикрепленные к мембранам эндоплазматической сети рибосомы. Как правило, они располагаются группами, на них тоже синтезируются белки, используемые самой клеткой.!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-19.jpg" alt="> The cytoskeleton is a three-dimensional network of filaments that permeates the cell. Supports"> Цитоскелет - трехмерная сеть нитей, которая пронизывает клетку. Поддерживает форму клетки, не позволяет органоидам перемещаться, защищает их от повреждения, является амортизатором. Состоит из микротрубочек и более мелких микрофиламентов. Микротрубочки построены из белка тубулина, микрофиламенты - из актина. Могут собираться и разбираться.!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-20.jpg" alt=">Cell wall The cell wall is the hard shell of the plant cell. It gives"> Клеточная стенка Клеточная стенка- твердая оболочка растительной клетки. Придает форму клетке. Защищает от повреждений. Она прозрачна, пропускает солнечный свет и воду. В ней есть поры, которые обеспечивают взаимосвязь клеток. Состоит из целлюлозы и матрикса. В матриксе содержится гемицеллюлоза и пектиновые вещества.!}

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-21.jpg" alt=">A vacuole is an organelle separated from the cytoplasm. The vacuole is filled with cellular"> Вакуоль - органоид, отделенный от цитоплазмы. Вакуоль заполнена клеточным соком. Вакуоль обеспечивает хранение !} various substances- ions, pigments, organic acids; lysis of substances, protection from herbivores, since it may contain a large amount of toxic substances; provides pigmentation - pigments are located in the vacuole; isolation of toxic substances.

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-22.jpg" alt=">Plastids - found only in cells higher plants and algae. The predecessor was "> Plastids - found only in the cells of higher plants and algae. The predecessor was a cyanobacterium, which became a symbiotic organism. It has a double membrane. Inside there is a circular DNA molecule, ribosomes. There are: 1) chloroplasts - green plastids in which photosynthesis occurs. 2) Chromoplasts - yellow, orange and red plastids. Formed by the destruction of chlorophyll (leaves in autumn, tomatoes, carrots)

Src="https://present5.com/presentation/3/3887616_437514243.pdf-img/3887616_437514243.pdf-23.jpg" alt=">3)Amyloplasts 3) Amyloplasts are uncolored plastids. Filled with starch."> 3)Амилопласты 3) Амилопласты - неокрашенные пластиды. Заполнены крахмалом. Выполняют запасающую функцию. (клубень картофеля). 4) Этиопласты - развиваются у растений, находящихся в темноте. Под воздействием света превращаются в хлоропласты Новые пластиды образуются за счет деления уже имеющихся пластид. При мутации нескольких пластид образуются химеры. У химер один лист может быть белым, а другой - зеленым или только часть листа будет белой.!}

Organelles are permanent components of a cell that perform specific functions.

Depending on their structural features, they are divided into membrane and non-membrane. Membrane organelles, in turn, are classified as single-membrane (endoplasmic reticulum, Golgi complex and lysosomes) or double-membrane (mitochondria, plastids and nucleus). Non-membrane The organelles are ribosomes, microtubules, microfilaments and the cell center. Of the listed organelles, only ribosomes are inherent in prokaryotes.

Structure and functions of the nucleus. Core- a large double-membrane organelle lying in the center of the cell or at its periphery. The dimensions of the nucleus can range from 3-35 microns. The shape of the nucleus is most often spherical or ellipsoidal, but there are also rod-shaped, fusiform, bean-shaped, lobed and even segmented nuclei. Some researchers believe that the shape of the nucleus corresponds to the shape of the cell itself.

Most cells have one nucleus, but, for example, in the cells of the liver and heart there can be two, and in a number of neurons - up to 15. Fibers skeletal muscles usually contain many nuclei, but they are not cells in the full sense of the word, since they are formed as a result of the fusion of several cells.

The core is surrounded nuclear membrane, and its internal space is filled nuclear juice, or nucleoplasm (karyoplasm), in which they are immersed chromatin And nucleolus. The kernel does the following essential functions, as storage and transmission of hereditary information, as well as control of cell activity (Fig. 2.30).

The role of the nucleus in the transmission of hereditary information was convincingly proven in experiments with the green alga Acetabularia. In a single giant cell, reaching a length of 5 cm, a cap, a stalk and a rhizoid are distinguished. Moreover, it contains only one nucleus located in the rhizoid. In the 1930s, I. Hemmerling transplanted the nucleus of one species of acetabularia with a green color into the rhizoid of another species, with a brown color, from which the nucleus had been removed (Fig. 2.31). After some time, the plant with the transplanted nucleus grew a new cap, like the nucleus donor algae. At the same time, the cap or stalk, separated from the rhizoid and not containing a nucleus, died after some time.

Nuclear envelope formed by two membranes - external and internal, between which there is space. The intermembrane space communicates with the cavity of the rough endoplasmic reticulum, and the outer membrane of the nucleus can carry ribosomes. The nuclear envelope is permeated with numerous pores lined with special proteins. Transport of substances occurs through the pores: necessary proteins (including enzymes), ions, nucleotides and other substances enter the nucleus, and RNA molecules, spent proteins, and ribosomal subunits leave it.

Thus, the functions nuclear envelope are the separation of the contents of the nucleus from the cytoplasm, as well as the regulation of metabolism between the nucleus and the cytoplasm.

Nucleoplasm is the content of the nucleus, in which chromatin and the nucleolus are immersed. It is a colloidal solution, chemically reminiscent of cytoplasm. Nucleoplasmic enzymes catalyze the exchange of amino acids, nucleotides, proteins, etc. Nucleoplasma is connected to hyaloplasma through nuclear pores. The functions of nucleoplasm, like hyaloplasm, are to ensure the interconnection of all structural components of the nucleus and to carry out a number of enzymatic reactions.

Chromatin is a collection of thin filaments and granules embedded in the nucleoplasm. It can only be detected by staining, since the refractive indices of chromatin and nucleoplasm are approximately the same. The filamentous component of chromatin is called euchromatin, and the granular component is called heterochromatin. Euchromatin is weakly compacted, since hereditary information is read from it, while more spiralized heterochromatin is genetically inactive.

Chromatin is a structural modification of chromosomes in a non-dividing nucleus. Thus, chromosomes are constantly present in the nucleus; only their state changes depending on the function that the nucleus performs at the moment.

The composition of chromatin mainly includes nucleoprotein proteins (deoxyribonucleoproteins and ribonucleoproteins), as well as enzymes, the most important of which are associated with the synthesis of nucleic acids, and some other substances.

The functions of chromatin consist, firstly, in the synthesis of specific of a given organism nucleic acids that direct the synthesis of specific proteins, secondly, in the transmission of hereditary properties from mother cell daughter, for which chromatin threads are packaged into chromosomes during division.

Nucleolus- a spherical body, clearly visible under a microscope, with a diameter of 1-3 microns. It is formed on sections of chromatin in which information about the structure of rRNA and ribosomal proteins is encoded. There is often only one nucleolus in the nucleus, but in those cells where intensive vital processes occur, there may be two or more nucleoli. The functions of the nucleoli are the synthesis of rRNA and the assembly of ribosomal subunits by combining rRNA with proteins coming from the cytoplasm.

Mitochondria- double-membrane organelles are round, oval or rod-shaped, although spiral-shaped ones are also found (in sperm). The diameter of mitochondria is up to 1 µm, and the length is up to 7 µm. The space inside the mitochondria is filled with matrix. The matrix is ​​the main substance of mitochondria. A circular DNA molecule and ribosomes are immersed in it. The outer membrane of mitochondria is smooth and impermeable to many substances. The inner membrane has projections - cristae, which increase the surface area of ​​the membranes for chemical reactions to occur (Fig. 2.32). On the surface of the membrane there are numerous protein complexes that make up the so-called respiratory chain, as well as mushroom-shaped ATP synthetase enzymes. The aerobic stage of respiration occurs in mitochondria, during which ATP is synthesized.

Plastids- large double-membrane organelles, characteristic only of plant cells. The internal space of plastids is filled with stroma, or matrix. The stroma contains a more or less developed system of membrane vesicles - thylakoids, which are collected in stacks - grana, as well as its own circular DNA molecule and ribosomes. There are four main types of plastids: chloroplasts, chromoplasts, leucoplasts and proplastids.

Chloroplasts- these are green plastids with a diameter of 3-10 microns, clearly visible under a microscope (Fig. 2.33). They are found only in the green parts of plants - leaves, young stems, flowers and fruits. Chloroplasts are generally oval or ellipsoidal in shape, but can also be cup-shaped, spiral-shaped, or even lobed. The number of chloroplasts in a cell averages from 10 to 100 pieces.

However, for example, in some algae it may be one, have significant dimensions and a complex shape - then it is called chromatophore. In other cases, the number of chloroplasts can reach several hundred, while their sizes are small. The color of chloroplasts is due to the main pigment of photosynthesis - chlorophyll, although they also contain additional pigments - carotenoids. Carotenoids become noticeable only in autumn, when chlorophyll in aging leaves is destroyed. The main function of chloroplasts is photosynthesis. Light reactions of photosynthesis occur on thylakoid membranes, on which chlorophyll molecules are attached, and dark reactions take place in the stroma, where numerous enzymes are contained.

Chromoplasts.- these are yellow, orange and red plastids containing carotenoid pigments. The shape of chromoplasts can also vary significantly: they can be tubular, spherical, crystalline, etc. Chromoplasts give color to the flowers and fruits of plants, attracting pollinators and distributors of seeds and fruits.

Leukoplasts- These are white or colorless plastids, mostly round or oval in shape. They are common in non-photosynthetic parts of plants, for example in the skin of leaves, potato tubers, etc. They store nutrients, most often starch, but in some plants it can be proteins or oil.

Plastids are formed in plant cells from proplastids, which are already present in the cells of educational tissue and are small double-membrane bodies. At the early stages of development, different types of plastids are capable of transforming into each other: when exposed to light, the leucoplasts of a potato tuber and the chromoplasts of a carrot root turn green.

Plastids and mitochondria are called semi-autonomous organelles of the cell, since they have their own DNA molecules and ribosomes, carry out protein synthesis and divide independently of cell division. These features are explained by their origin from single-celled prokaryotic organisms. However, the “independence” of mitochondria and plastids is limited, since their DNA contains too few genes for free existence, while the rest of the information is encoded in the chromosomes of the nucleus, which allows it to control these organelles.

Endoplasmic reticulum(EPS), or endoplasmic reticulum(ER) is a single-membrane organelle, which is a network of membrane cavities and tubules occupying up to 30% of the contents of the cytoplasm. The diameter of the EPS tubules is about 25-30 nm. There are two types of EPS - rough and smooth. Rough XPS carries ribosomes, protein synthesis occurs on it (Fig. 2.34).

Smooth XPS lacks ribosomes. Its function is the synthesis of lipids and carbohydrates, the formation of lysosomes, as well as the transport, storage and neutralization of toxic substances. It is especially developed in those cells where intensive metabolic processes occur, for example in liver cells - hepatocytes - and skeletal muscle fibers. Substances synthesized in the ER are transported to the Golgi apparatus. The assembly of cell membranes also occurs in the ER, but their formation is completed in the Golgi apparatus.

Golgi apparatus, or Golgi complex- single-membrane organelle, formed by the system flat cisterns, tubules and vesicles detached from them (Fig. 2.35).

The structural unit of the Golgi apparatus is dictyosome- a stack of tanks, at one pole of which substances from the EPS come, and from the opposite pole, having undergone certain transformations, they are packed into vesicles and sent to other parts of the cell. The diameter of the tanks is about 2 microns, and the diameter of small bubbles is about 20-30 microns. The main functions of the Golgi complex are the synthesis of certain substances and modification (change) of proteins, lipids and carbohydrates coming from the ER, the final formation of membranes, as well as the transport of substances throughout the cell, renewal of its structures and the formation of lysosomes. The Golgi apparatus received its name in honor of the Italian scientist Camillo Golgi, who first discovered this organelle (1898).

Lysosomes- small single-membrane organelles up to 1 μm in diameter, which contain hydrolytic enzymes involved in intracellular digestion. The membranes of lysosomes are poorly permeable to these enzymes, so the lysosomes perform their functions very accurately and targetedly. Thus, they take an active part in the process of phagocytosis, forming digestive vacuoles, and in case of starvation or damage to certain parts of the cell, they digest them without affecting others. The role of lysosomes in cell death processes has recently been discovered.

Vacuole is a cavity in the cytoplasm of plant and animal cells, bounded by a membrane and filled with liquid. Digestive and contractile vacuoles are found in protozoan cells. The former take part in the process of phagocytosis, as they break down nutrients. The latter provide maintenance water-salt balance due to osmoregulation. In multicellular animals, digestive vacuoles are mainly found.

In plant cells, vacuoles are always present; they are surrounded by a special membrane and filled with cell sap. The membrane surrounding the vacuole is similar in chemical composition, structure and functions to the plasma membrane. Cell sap represents water solution various inorganic and organic substances, including mineral salts, organic acids, carbohydrates, proteins, glycosides, alkaloids, etc. The vacuole can occupy up to 90% of the cell volume and push the nucleus to the periphery. This part of the cell performs storage, excretory, osmotic, protective, lysosomal and other functions, since it accumulates nutrients and waste products, ensures the supply of water and maintains the shape and volume of the cell, and also contains enzymes for the breakdown of many cell components. Moreover, biologically active substances vacuoles can prevent many animals from eating these plants. In a number of plants, due to the swelling of vacuoles, cell growth occurs by elongation.

Vacuoles are also present in the cells of some fungi and bacteria, but in fungi they perform only the function of osmoregulation, while in cyanobacteria they maintain buoyancy and participate in the process of assimilation of nitrogen from the air.

Ribosomes- small non-membrane organelles with a diameter of 15-20 microns, consisting of two subunits - large and small (Fig. 2.36).

Eukaryotic ribosomal subunits are assembled in the nucleolus and then transported into the cytoplasm. Ribosomes in prokaryotes, mitochondria, and plastids are smaller in size than ribosomes in eukaryotes. Ribosomal subunits include rRNA and proteins.

The number of ribosomes per cell can reach several tens of millions: in the cytoplasm, mitochondria and plastids they are in a free state, and on the rough ER they are bound. They take part in protein synthesis, in particular, they carry out the process of translation - the biosynthesis of a polypeptide chain on an mRNA molecule. Free ribosomes synthesize the proteins of hyaloplasm, mitochondria, plastids, and their own ribosomal proteins, while ribosomes attached to the rough ER carry out the translation of proteins for removal from cells, membrane assembly, and the formation of lysosomes and vacuoles.

Ribosomes can be found singly in the hyaloplasm or assembled in groups during the simultaneous synthesis of several polypeptide chains on one mRNA. Such groups of ribosomes are called polyribosomes, or polysomes(Fig. 2.37).

Microtubules- These are cylindrical hollow non-membrane organelles that penetrate the entire cytoplasm of the cell. Their diameter is about 25 nm, wall thickness is 6-8 nm. They are formed by numerous protein molecules tubulin, which first form 13 threads resembling beads and then assemble into a microtubule. Microtubules form a cytoplasmic reticulum, which gives the cell shape and volume, connects the plasma membrane with other parts of the cell, ensures the transport of substances throughout the cell, takes part in the movement of the cell and intracellular components, as well as in the division of genetic material. They are part of the cell center and organelles of movement - flagella and cilia.

Microfilaments, or microthreads, are also non-membrane organelles, however, they have a filamentous shape and are formed not by tubulin, but actin. They take part in the processes of membrane transport, intercellular recognition, division of the cell cytoplasm and in its movement. IN muscle cells the interaction of actin microfilaments with myosin filaments ensures contraction.

Microtubules and microfilaments form internal skeleton cells - cytoskeleton. It is a complex network of fibers that provide mechanical support for the plasma membrane, determines the shape of the cell, the location of cellular organelles and their movement during cell division (Fig. 2.38).

Cell center- a non-membrane organelle located in animal cells near the nucleus; it is absent in plant cells (Fig. 2.39). Its length is about 0.2-0.3 microns, and its diameter is 0.1-0.15 microns. The cell center is formed by two centrioles, lying in mutually perpendicular planes, and radiant sphere from microtubules. Each centriole is formed by nine groups of microtubules, collected in groups of three, i.e., triplets. The cellular center takes part in the processes of microtubule assembly, division of the cell's hereditary material, as well as in the formation of flagella and cilia.

Organelles of movement. Flagella And cilia They are cell outgrowths covered with plasmalemma. The basis of these organelles is made up of nine pairs of microtubules located along the periphery and two free microtubules in the center (Fig. 2.40). Microtubules are interconnected by various proteins, ensuring their coordinated deviation from the axis - oscillation. Oscillations are energy-dependent, that is, the energy of high-energy ATP bonds is spent on this process. ATP breakdown is a function basal bodies, or kinetosomes, flagella and cilia located at the base.

The length of cilia is about 10-15 nm, and flagella - 20-50 µm. Due to the strictly directed movements of flagella and cilia, not only the movement of single-celled animals, sperm, etc. is carried out, but also cleaning occurs respiratory tract, the movement of the egg through the fallopian tubes, since all these parts of the human body are lined with ciliated epithelium.

Organoids – permanent and essential components of cells; specialized areas of the cell cytoplasm that have a specific structure and perform specific functions in the cell. There are organelles of general and special purpose.

General purpose organelles are present in most cells (endoplasmic reticulum, mitochondria, plastids, Golgi complex, lysosomes, vacuoles, cell center, ribosomes). Organelles for special purposes are characteristic only of specialized cells (myofibrils, flagella, cilia, contractile and digestive vacuoles). Organelles (with the exception of ribosomes and the cell center) have a membrane structure.

Endoplasmic reticulum (ER) – This is a branched system of interconnected cavities, tubes and channels formed by elementary membranes and penetrating the entire thickness of the cell. Opened in 1943 by Porter. There are especially many endoplasmic reticulum channels in cells with intense metabolism. On average, the volume of the EPS ranges from 30% to 50% of the total cell volume. EPS is labile. Shape of internal lacunae and cana

fish, their size, location in the cell and quantity change during life. The cell is more developed in animals. The ER is morphologically and functionally connected with the boundary layer of the cytoplasm, the nuclear envelope, ribosomes, the Golgi complex, and vacuoles, forming together with them a single functional and structural system for the metabolism and energy and movement of substances within the cell. Mitochondria and plastids accumulate near the endoplasmic reticulum.

There are two types of EPS: rough and smooth. Enzymes of the fat and carbohydrate synthesis systems are localized on the membranes of the smooth (agranular) ER: the synthesis of carbohydrates and almost all cellular lipids occurs here. Membranes of the smooth variety of the endoplasmic reticulum predominate in the cells of the sebaceous glands, liver (glycogen synthesis), in cells with high content nutrients (plant seeds). Ribosomes are located on the membrane of the rough (granular) EPS, where protein biosynthesis occurs. Some of the proteins they synthesize are included in the membrane of the endoplasmic reticulum, the rest enter the lumen of its channels, where they are converted and transported to the Golgi complex. There are especially many rough membranes in gland cells and nerve cells.

Rice. Rough and smooth endoplasmic reticulum.

Rice. Transport of substances through the nucleus – endoplasmic reticulum (ER) – Golgi complex system.

Functions of the endoplasmic reticulum:

1) synthesis of proteins (rough EPS), carbohydrates and lipids (smooth EPS);

2) transport of substances, both entering the cell and newly synthesized;

3) division of the cytoplasm into compartments (compartments), which ensures the spatial separation of enzyme systems necessary for their sequential entry into biochemical reactions.

Mitochondria – are present in almost all types of cells of uni- and multicellular organisms (with the exception of mammalian erythrocytes). Their number in different cells varies and depends on the level of functional activity of the cell. In a rat liver cell there are about 2500 of them, and in the male reproductive cell of some mollusks there are 20 - 22. There are more of them in pectoral muscle flying birds than in the pectoral muscle of flightless birds.

Mitochondria have the shape of spherical, oval and cylindrical bodies. The dimensions are 0.2 - 1.0 microns in diameter and up to 5 - 7 microns in length.

Rice. Mitochondria.

The length of filamentous forms reaches 15-20 microns. On the outside, mitochondria are bounded by a smooth outer membrane, similar in composition to the plasmalemma. The inner membrane forms numerous outgrowths - cristae - and contains numerous enzymes, ATP-somes (mushroom bodies), involved in the processes of transformation of nutrient energy into ATP energy. The number of cristae depends on the function of the cell. There are a lot of cristae in muscle mitochondria; they occupy the entire internal cavity of the organelle. In the mitochondria of embryonic cells, cristae are rare. In plants, the outgrowths of the inner membrane often have the shape of tubes. The mitochondrial cavity is filled with a matrix that contains water, mineral salts, enzyme proteins, and amino acids. Mitochondria have an autonomous protein-synthesizing system: a circular DNA molecule, various types of RNA, and ribosomes that are smaller than those in the cytoplasm.

Mitochondria are closely connected by membranes of the endoplasmic reticulum, whose channels often open directly into the mitochondria. With increasing load on the organ and intensification of synthetic processes that require energy, contacts between the EPS and mitochondria become especially numerous. The number of mitochondria can increase rapidly by fission. The ability of mitochondria to reproduce is due to the presence of a DNA molecule in them, reminiscent of the circular chromosome of bacteria.

Functions of mitochondria:

1) synthesis of a universal energy source - ATP;

2) synthesis steroid hormones;

3) biosynthesis of specific proteins.

Plastids - organelles with a membrane structure, characteristic only of plant cells. The processes of synthesis of carbohydrates, proteins and fats take place in them. Based on their pigment content, they are divided into three groups: chloroplasts, chromoplasts and leucoplasts.

Chloroplasts have a relatively constant elliptical or lens-shaped shape. The largest diameter size is 4 – 10 microns. The number in a cell ranges from a few units to several dozen. Their size, color intensity, number and location in the cell depend on lighting conditions, type and physiological state plants.

Rice. Chloroplast, structure.

These are protein-lipid bodies, consisting of 35-55% protein, 20-30% lipids, 9% chlorophyll, 4-5% carotenoids, 2-4% nucleic acids. The amount of carbohydrates varies; a certain amount was found minerals Chlorophyll is an ester of an organic dibasic acid - chlorophyllin and organic alcohols - methyl (CH 3 OH) and phytol (C 20 H 39 OH). In higher plants, chlorophyll a is constantly present in the chloroplasts - it has a blue-green color, and chlorophyll b - yellow-green; Moreover, the chlorophyll content is several times higher.

In addition to chlorophyll, chloroplasts include pigments - carotene C 40 H 56 and xanthophyll C 40 H 56 O 2 and some other pigments (carotenoids). In a green leaf, the yellow satellites of chlorophyll are masked by a brighter green color. However, in the fall, when leaves fall, chlorophyll is destroyed in most plants and then the presence of carotenoids in the leaf is detected - the leaf turns yellow.

The chloroplast is covered with a double shell, consisting of outer and inner membranes. The internal contents - the stroma - have a lamellar (lamellar) structure. In the colorless stroma, grana are distinguished - green-colored bodies, 0.3 - 1.7 μm. They are a collection of thylakoids - closed bodies in the form of flat vesicles or disks of membrane origin. Chlorophyll in the form of a monomolecular layer is located between the protein and lipid layers in close connection with them. The spatial arrangement of pigment molecules in the membrane structures of chloroplasts is very appropriate and creates optimal conditions for the most efficient absorption, transmission and use of radiant energy. Lipids form the anhydrous dielectric layers of the chloroplast membranes necessary for the functioning of the electron transport chain. The role of links in the electron transport chain is performed by proteins (cytochromes, plastoquinones, ferredoxin, plastocyanin) and individual chemical elements– iron, manganese, etc. The number of grains in a chloroplast is from 20 to 200. Between the grains, connecting them to each other, stromal lamellae are located. Granular lamellae and stromal lamellae have a membrane structure.

The internal structure of the chloroplast makes possible the spatial separation of numerous and diverse reactions that together constitute the content of photosynthesis.

Chloroplasts, like mitochondria, contain specific RNA and DNA, as well as smaller ribosomes and the entire molecular arsenal necessary for protein biosynthesis. These organelles have a sufficient amount of mRNA to ensure maximum activity of the protein synthesizing system. At the same time, they also contain enough DNA to encode certain proteins. They reproduce by division, by simple constriction.

It has been established that chloroplasts can change their shape, size and position in the cell, that is, they are able to move independently (chloroplast taxi). Two types of contractile proteins were found in them, due to which, obviously, the active movement of these organelles in the cytoplasm occurs.

Chromoplasts are widely distributed in the generative organs of plants. They color the petals of flowers (buttercup, dahlia, sunflower) and fruits (tomatoes, rowan berries, rose hips) yellow, orange, and red. IN vegetative organs chromoplasts are much less common.

The color of chromoplasts is due to the presence of carotenoids - carotene, xanthophyll and lycopene, which are found in plastids different condition: in the form of crystals, lipoid solution or in combination with proteins.

Chromoplasts, compared to chloroplasts, have a simpler structure - they lack a lamellar structure. Chemical composition also different: pigments – 20–50%, lipids up to 50%, proteins – about 20%, RNA – 2-3%. This indicates less physiological activity of chloroplasts.

Leukoplasts do not contain pigments and are colorless. These smallest plastids are round, ovoid or rod-shaped. In a cell they are often grouped around the nucleus.

The internal structure is even less differentiated compared to chloroplasts. They carry out the synthesis of starch, fats, and proteins. In accordance with this, three types of leukoplasts are distinguished - amyloplasts (starch), oleoplasts ( vegetable oils) and proteoplasts (proteins).

Leucoplasts arise from proplastids, with which they are similar in shape and structure, differing only in size.

All plastids are genetically related to each other. They are formed from proplastids - tiny colorless cytoplasmic formations, similar in appearance with mitochondria. Proplastids are found in spores, eggs, and embryonic growth point cells. Chloroplasts (in the light) and leucoplasts (in the dark) are formed directly from proplastids, and chromoplasts develop from them, which are the final product in the evolution of plastids in the cell.

Golgi complex - was first discovered in 1898 by the Italian scientist Golgi in animal cells. This is the system internal cavities, cisterns (5-20), located close together and parallel to each other, and large and small vacuoles. All these formations have a membrane structure and are specialized sections of the endoplasmic reticulum. In animal cells the Golgi complex is better developed than in plant cells; in the latter it is called dictyosomes.

Rice. The structure of the Golgi complex.

Proteins and lipids entering the lamellar complex undergo various transformations, accumulate, sort, package into secretory vesicles and are transported to their destination: to various structures inside the cell or outside the cell. The membranes of the Golgi complex also synthesize polysaccharides and form lysosomes. In mammary gland cells, the Golgi complex is involved in the formation of milk, and in liver cells - bile.

Functions of the Golgi complex:

1) concentration, dehydration and compaction of proteins, fats, polysaccharides and substances synthesized in the cell and received from the outside;

2) assembly of complex complexes of organic substances and preparation of them for removal from the cell (cellulose and hemicellulose in plants, glycoproteins and glycolipids in animals);

3) synthesis of polysaccharides;

4) formation of primary lysosomes.

Lysosomes - small oval bodies with a diameter of 0.2-2.0 microns. Central position occupies a vacuole containing 40 (according to various sources 30-60) hydrolytic enzymes capable of acidic environment(pH 4.5-5) break down proteins, nucleic acids, polysaccharides, lipids and other substances.

Around this cavity there is a stroma, covered on the outside with an elementary membrane. The breakdown of substances with the help of enzymes is called lysis, which is why the organelle is called a lysosome. The formation of lysosomes occurs in the Golgi complex. Primary lysosomes approach directly the pinocytotic or phagocytotic vacuoles (endosomes) and pour their contents into their cavity, forming secondary lysosomes (phagosomes), within which the digestion of substances occurs. The lysis products enter the cytoplasm through the lysosome membrane and are included in further metabolism. Secondary lysosomes with remnants of undigested substances are called residual bodies. An example of secondary lysosomes are the digestive vacuoles of protozoa.

Functions of lysosomes:

1) intracellular digestion of food macromolecules and foreign components entering the cell during pineal and phagocytosis, providing the cell with additional raw materials for biochemical and energy processes;

2) during fasting, lysosomes digest some organelles and replenish the supply of nutrients for some time;

3) destruction of temporary organs of embryos and larvae (tail and gills in a frog) during postembryonic development;

Rice. Lysosome formation

Vacuoles – cavities in the cytoplasm of plant cells and protists filled with liquid. They have the form of vesicles, thin tubules and others. Vacuoles are formed from extensions of the endoplasmic reticulum and vesicles of the Golgi complex as the thinnest cavities, then as the cell grows and the accumulation of metabolic products, their volume increases and their number decreases. A developed, formed cell usually has one large vacuole occupying a central position.

The vacuoles of plant cells are filled with cell sap, which is an aqueous solution of organic (malic, oxalic, citric acids, sugars, inulin, amino acids, proteins, tannins, alkaloids, glucosides) and mineral (nitrates, chlorides, phosphates) substances.

In protists, digestive vacuoles and contractile vacuoles are found.

Functions of vacuoles:

1) storage of reserve nutrients and receptacles for excretions (in plants);

2) determine and maintain osmotic pressure in cells;

3) provide intracellular digestion in protists.

Rice. Cellular center.

Cell center usually located near the nucleus and consists of two centrioles located perpendicular to each other and surrounded by the radiate sphere. Each centriole is a hollow cylindrical body 0.3-0.5 µm long and 0.15 µm long, the wall of which is formed by 9 triplets of microtubules. If the centriole lies at the base of the cilium or flagellum, then it is called basal body.

Before division, the centrioles diverge to opposite poles and a daughter centriole appears near each of them. From centrioles located at different poles of the cell, microtubules are formed that grow towards each other. They form the mitotic spindle, which promotes the uniform distribution of genetic material between daughter cells, and are the center of cytoskeletal organization. Some of the spindle threads are attached to the chromosomes. In the cells of higher plants, the cell center does not have centrioles.

Centrioles are self-replicating organelles of the cytoplasm. They arise as a result of duplication of existing ones. This occurs when the centrioles separate. The immature centriole contains 9 single microtubules; Apparently, each microtubule is a template for the assembly of triplets characteristic of a mature centriole.

The centrosome is characteristic of animal cells, some fungi, algae, mosses and ferns.

Functions of the cell center:

1) the formation of division poles and the formation of spindle microtubules.

Ribosomes - small spherical organelles, from 15 to 35 nm. They consist of two subunits, large (60S) and small (40S). Contain about 60% protein and 40% ribosomal RNA. rRNA molecules form its structural framework. Most proteins are specifically bound to certain regions of rRNA. Some proteins are included in ribosomes only during protein biosynthesis. Ribosomal subunits are formed in the nucleoli. and through pores in the nuclear envelope enter the cytoplasm, where they are located either on the EPA membrane or on outside nuclear membrane, or freely in the cytoplasm. First, rRNA is synthesized on nucleolar DNA, which is then covered with ribosomal proteins coming from the cytoplasm and cleaved to required sizes and form ribosomal subunits. There are no fully formed ribosomes in the nucleus. The combination of subunits into a whole ribosome occurs in the cytoplasm, usually during protein biosynthesis. Compared to mitochondria, plastids, and prokaryotic cells, ribosomes in the cytoplasm of eukaryotic cells are larger. They can combine 5-70 units into polysomes.

Functions of ribosomes:

1) participation in protein biosynthesis.

Rice. 287. Ribosome: 1 - small subunit; 2 - large subunit.

Cilia, flagella – outgrowths of the cytoplasm covered with an elementary membrane, under which there are 20 microtubules, forming 9 pairs along the periphery and two single ones in the center. At the base of the cilia and flagella there are basal bodies. The length of the flagella reaches 100 µm. Cilia are short – 10-20 microns – flagella. The movement of the flagella is screw-shaped, and the movement of the cilia is paddle-shaped. Thanks to cilia and flagella, bacteria, protists, ciliated animals move, particles or liquids (cilia of the ciliated epithelium of the respiratory tract, oviducts), and germ cells (spermatozoa) move.

Rice. The structure of flagella and cilia in eukaryotes

Inclusions - temporary components of the cytoplasm, appearing and disappearing. As a rule, they are contained in cells at certain stages life cycle. The specificity of the inclusions depends on the specificity of the corresponding tissue cells and organs. Inclusions are found primarily in plant cells. They can occur in the hyaloplasm, various organelles, and less commonly in the cell wall.

Functionally, inclusions are either compounds temporarily removed from cell metabolism (reserve substances - starch grains, lipid droplets and protein deposits) or end products of metabolism (crystals of certain substances).

Starch grains. These are the most common inclusions of plant cells. Starch is stored in plants exclusively in the form of starch grains. They are formed only in the stroma of plastids of living cells. During photosynthesis, green leaves produce assimilation, or primary starch. Assimilative starch does not accumulate in the leaves and, quickly hydrolyzing to sugars, flows into the parts of the plant in which its accumulation occurs. There it turns back into starch, which is called secondary. Secondary starch is also formed directly in tubers, rhizomes, seeds, that is, where it is stored. Then they call him spare. Leucoplasts that accumulate starch are called amyloplasts. Particularly rich in starch are the seeds, underground shoots (tubers, bulbs, rhizomes), and the parenchyma of the conducting tissues of the roots and stems of woody plants.

Lipid drops. Found in almost all plant cells. Seeds and fruits are the richest in them. Fixed oils in the form of lipid droplets - the second most important (after starch) form of reserve nutrients. The seeds of some plants (sunflower, cotton, etc.) can accumulate up to 40% oil by dry matter weight.

Lipid droplets, as a rule, accumulate directly in the hyaloplasm. They are spherical bodies, usually of submicroscopic size. Lipid droplets can also accumulate in leukoplasts, which are called elaioplasts.

Protein inclusions are formed in various organelles of the cell in the form of amorphous or crystalline deposits of various shapes and structures. Most often, crystals can be found in the nucleus - in the nucleoplasm, sometimes in the perinuclear space, less often in the hyaloplasm, plastid stroma, in the extensions of the ER cisterns, peroxisomal matrix and mitochondria. Vacuoles contain both crystalline and amorphous protein inclusions. IN the greatest number protein crystals are found in the storage cells of dry seeds in the form of so-called aleurone 3 grains or protein bodies.

Storage proteins are synthesized by ribosomes during seed development and deposited in vacuoles. When seeds ripen, accompanied by dehydration, protein vacuoles dry out and the protein crystallizes. As a result of this, in a mature dry seed, protein vacuoles are converted into protein bodies (aleurone grains).