Organoids- permanent, necessarily present, components of the cell that perform specific functions.
Endoplasmic reticulum
Endoplasmic reticulum (ER), or endoplasmic reticulum (ER), is a single-membrane organelle. It is a system of membranes that form “cisterns” and channels, connected to each other and delimiting a single internal space - the EPS cavities. The membranes are connected on one side to the cytoplasmic membrane and on the other to the outer nuclear membrane. There are two types of EPS: 1) rough (granular), containing ribosomes on its surface, and 2) smooth (agranular), the membranes of which do not carry ribosomes.
Functions: 1) transport of substances from one part of the cell to another, 2) division of the cell cytoplasm into compartments (“compartments”), 3) synthesis of carbohydrates and lipids (smooth ER), 4) protein synthesis (rough ER), 5) place of formation of the Golgi apparatus .
Or Golgi complex, is a single-membrane organelle. It consists of stacks of flattened “cisterns” with widened edges. Associated with them is a system of small single-membrane vesicles (Golgi vesicles). Each stack usually consists of 4-6 “cisterns”, is a structural and functional unit of the Golgi apparatus and is called a dictyosome. The number of dictyosomes in a cell ranges from one to several hundred. In plant cells, dictyosomes are isolated.
The Golgi apparatus is usually located near the cell nucleus (in animal cells, often near the cell center).
Functions of the Golgi apparatus: 1) accumulation of proteins, lipids, carbohydrates, 2) modification of incoming organic substances, 3) “packaging” of proteins, lipids, carbohydrates into membrane vesicles, 4) secretion of proteins, lipids, carbohydrates, 5) synthesis of carbohydrates and lipids, 6) place of formation lysosomes The secretory function is the most important, therefore the Golgi apparatus is well developed in secretory cells.
Lysosomes
Lysosomes- single-membrane organelles. They are small bubbles (diameter from 0.2 to 0.8 microns) containing a set of hydrolytic enzymes. Enzymes are synthesized on the rough ER and move to the Golgi apparatus, where they are modified and packaged into membrane vesicles, which, after separation from the Golgi apparatus, become lysosomes themselves. A lysosome can contain from 20 to 60 various types hydrolytic enzymes. The breakdown of substances using enzymes is called lysis.
There are: 1) primary lysosomes, 2) secondary lysosomes. Primary are called lysosomes that are detached from the Golgi apparatus. Primary lysosomes are a factor ensuring the exocytosis of enzymes from the cell.
Secondary are called lysosomes formed as a result of the fusion of primary lysosomes with endocytic vacuoles. In this case, they digest substances that enter the cell by phagocytosis or pinocytosis, so they can be called digestive vacuoles.
Autophagy- the process of destroying structures unnecessary for the cell. First, the structure to be destroyed is surrounded by a single membrane, then the resulting membrane capsule merges with the primary lysosome, resulting in the formation of a secondary lysosome (autophagic vacuole), in which this structure is digested. The products of digestion are absorbed by the cell cytoplasm, but some of the material remains undigested. The secondary lysosome containing this undigested material is called a residual body. By exocytosis, undigested particles are removed from the cell.
Autolysis- cell self-destruction, which occurs due to the release of lysosome contents. Normally, autolysis occurs during metamorphosis (disappearance of the tail in a tadpole of frogs), involution of the uterus after childbirth, and in areas of tissue necrosis.
Functions of lysosomes: 1) intracellular digestion of organic substances, 2) destruction of unnecessary cellular and non-cellular structures, 3) participation in the processes of cell reorganization.
Vacuoles
Vacuoles- single-membrane organelles, are “containers” filled aqueous solutions organic and inorganic substances. The ER and Golgi apparatus take part in the formation of vacuoles. Young plant cells contain many small vacuoles, which then, as the cells grow and differentiate, merge with each other and form one large central vacuole. The central vacuole can occupy up to 95% of the volume of a mature cell; the nucleus and organelles are pushed towards the cell membrane. The membrane bounding the plant vacuole is called the tonoplast. The fluid that fills a plant vacuole is called cell sap . The composition of cell sap includes water-soluble organic and inorganic salts, monosaccharides, disaccharides, amino acids, final or toxic metabolic products (glycosides, alkaloids), and some pigments (anthocyanins).
Animal cells contain small digestive and autophagy vacuoles, which belong to the group of secondary lysosomes and contain hydrolytic enzymes. Unicellular animals also have contractile vacuoles that perform the function of osmoregulation and excretion.
Functions of the vacuole: 1) accumulation and storage of water, 2) regulation water-salt metabolism, 3) maintenance of turgor pressure, 4) accumulation of water-soluble metabolites, reserve nutrients, 5) coloring flowers and fruits and thereby attracting pollinators and seed dispersers, 6) see the functions of lysosomes.
The endoplasmic reticulum, Golgi apparatus, lysosomes and vacuoles form single vacuolar network of the cell, the individual elements of which can transform into each other.
Mitochondria
1 - outer membrane;
2 - internal membrane; 3 - matrix; 4 - crista; 5 - multienzyme system; 6 - circular DNA.
The shape, size and number of mitochondria vary enormously. Mitochondria can be rod-shaped, round, spiral, cup-shaped, or branched in shape. The length of mitochondria ranges from 1.5 to 10 µm, diameter - from 0.25 to 1.00 µm. The number of mitochondria in a cell can reach several thousand and depends on the metabolic activity of the cell.
The mitochondrion is bounded by two membranes. The outer membrane of mitochondria (1) is smooth, the inner (2) forms numerous folds - cristas(4). Cristae increase the surface area of the inner membrane, on which multienzyme systems (5) involved in the synthesis of ATP molecules are located. The internal space of mitochondria is filled with matrix (3). The matrix contains circular DNA (6), specific mRNA, prokaryotic type ribosomes (70S type), and Krebs cycle enzymes.
Mitochondrial DNA is not associated with proteins (“naked”), is attached to the inner membrane of the mitochondrion and carries information about the structure of about 30 proteins. To build a mitochondrion, many more proteins are required, so information about most mitochondrial proteins is contained in nuclear DNA, and these proteins are synthesized in the cytoplasm of the cell. Mitochondria are capable of autonomous reproduction by fission in two. Between the outer and inner membranes there is proton reservoir, where H + accumulation occurs.
Functions of mitochondria: 1) ATP synthesis, 2) oxygen breakdown of organic substances.
According to one hypothesis (the theory of symbiogenesis), mitochondria originated from ancient free-living aerobic prokaryotic organisms, which, having accidentally penetrated the host cell, then formed a mutually beneficial symbiotic complex with it. The following data support this hypothesis. Firstly, mitochondrial DNA has the same structural features as the DNA of modern bacteria (closed in a ring, not associated with proteins). Secondly, mitochondrial ribosomes and bacterial ribosomes belong to the same type - the 70S type. Thirdly, the mechanism of mitochondrial fission is similar to that of bacteria. Fourth, the synthesis of mitochondrial and bacterial proteins is suppressed by the same antibiotics.
Plastids
1 - outer membrane; 2 - internal membrane; 3 - stroma; 4 - thylakoid; 5 - grana; 6 - lamellae; 7 - starch grains; 8 - lipid drops.
Plastids are characteristic only of plant cells. Distinguish three main types of plastids: leucoplasts - colorless plastids in the cells of uncolored parts of plants, chromoplasts - colored plastids usually yellow, red and orange flowers chloroplasts are green plastids.
Chloroplasts. In the cells of higher plants, chloroplasts have the shape of a biconvex lens. The length of chloroplasts ranges from 5 to 10 µm, diameter - from 2 to 4 µm. Chloroplasts are bounded by two membranes. The outer membrane (1) is smooth, the inner (2) has a complex folded structure. The smallest fold is called thylakoid(4). A group of thylakoids arranged like a stack of coins is called facet(5). The chloroplast contains on average 40-60 grains, arranged in a checkerboard pattern. The granae are connected to each other by flattened channels - lamellae(6). The thylakoid membranes contain photosynthetic pigments and enzymes that provide ATP synthesis. The main photosynthetic pigment is chlorophyll, which determines green color chloroplasts.
The interior space of the chloroplasts is filled stroma(3). The stroma contains circular “naked” DNA, 70S-type ribosomes, Calvin cycle enzymes, and starch grains (7). Inside each thylakoid there is a proton reservoir, and H + accumulates. Chloroplasts, like mitochondria, are capable of autonomous reproduction by dividing into two. They are found in the cells of the green parts of higher plants, especially many chloroplasts in leaves and green fruits. Chloroplasts of lower plants are called chromatophores.
Function of chloroplasts: photosynthesis. It is believed that chloroplasts originated from ancient endosymbiotic cyanobacteria (symbiogenesis theory). The basis for this assumption is the similarity of chloroplasts and modern bacteria in a number of characteristics (circular, “naked” DNA, 70S-type ribosomes, method of reproduction).
Leukoplasts. The shape varies (spherical, round, cupped, etc.). Leukoplasts are bounded by two membranes. The outer membrane is smooth, the inner one forms few thylakoids. The stroma contains circular “naked” DNA, 70S-type ribosomes, enzymes for the synthesis and hydrolysis of reserve nutrients. There are no pigments. The cells of the underground organs of the plant (roots, tubers, rhizomes, etc.) have especially many leucoplasts. Function of leucoplasts: synthesis, accumulation and storage of reserve nutrients. Amyloplasts- leukoplasts that synthesize and accumulate starch, elaioplasts- oils, proteinoplasts- proteins. Different substances can accumulate in the same leukoplast.
Chromoplasts. Bounded by two membranes. The outer membrane is smooth, the inner membrane is either smooth or forms single thylakoids. The stroma contains circular DNA and pigments - carotenoids, which give chromoplasts a yellow, red or orange color. The form of accumulation of pigments is different: in the form of crystals, dissolved in lipid droplets (8), etc. Contained in the cells of mature fruits, petals, autumn leaves, and rarely - root vegetables. Chromoplasts are considered the final stage of plastid development.
Function of chromoplasts: coloring flowers and fruits and thereby attracting pollinators and seed dispersers.
All types of plastids can be formed from proplastids. Proplastids- small organelles contained in meristematic tissues. Since plastids have a common origin, interconversions between them are possible. Leukoplasts can turn into chloroplasts (greening of potato tubers in the light), chloroplasts - into chromoplasts (yellowing of leaves and reddening of fruits). The transformation of chromoplasts into leucoplasts or chloroplasts is considered impossible.
Ribosomes
1 - large subunit; 2 - small subunit.
Ribosomes- non-membrane organelles, diameter approximately 20 nm. Ribosomes consist of two subunits - large and small, into which they can dissociate. Chemical composition ribosomes - proteins and rRNA. rRNA molecules make up 50-63% of the mass of the ribosome and form its structural framework. There are two types of ribosomes: 1) eukaryotic (with sedimentation constants for the whole ribosome - 80S, small subunit - 40S, large - 60S) and 2) prokaryotic (70S, 30S, 50S, respectively).
Ribosomes of the eukaryotic type contain 4 rRNA molecules and about 100 protein molecules, while the prokaryotic type contains 3 rRNA molecules and about 55 protein molecules. During protein biosynthesis, ribosomes can “work” individually or combine into complexes - polyribosomes (polysomes). In such complexes they are linked to each other by one mRNA molecule. Prokaryotic cells have only 70S-type ribosomes. Eukaryotic cells have both 80S-type ribosomes (rough EPS membranes, cytoplasm) and 70S-type (mitochondria, chloroplasts).
Eukaryotic ribosomal subunits are formed in the nucleolus. The combination of subunits into a whole ribosome occurs in the cytoplasm, usually during protein biosynthesis.
Function of ribosomes: assembly of a polypeptide chain (protein synthesis).
Cytoskeleton
Cytoskeleton formed by microtubules and microfilaments. Microtubules are cylindrical, unbranched structures. The length of microtubules ranges from 100 µm to 1 mm, the diameter is approximately 24 nm, and the wall thickness is 5 nm. The main chemical component is the protein tubulin. Microtubules are destroyed by colchicine. Microfilaments are filaments with a diameter of 5-7 nm and consist of the protein actin. Microtubules and microfilaments form complex weaves in the cytoplasm. Functions of the cytoskeleton: 1) determination of the shape of the cell, 2) support for organelles, 3) formation of the spindle, 4) participation in cell movements, 5) organization of cytoplasmic flow.
Includes two centrioles and a centrosphere. Centriole is a cylinder, the wall of which is formed by nine groups of three fused microtubules (9 triplets), interconnected at certain intervals by cross-links. Centrioles are united in pairs where they are located at right angles to each other. Before cell division, centrioles diverge to opposite poles, and a daughter centriole appears near each of them. They form a division spindle, which contributes to the even distribution of genetic material between daughter cells. In the cells of higher plants (gymnosperms, angiosperms), the cell center does not have centrioles. Centrioles are self-replicating organelles of the cytoplasm; they arise as a result of duplication of existing centrioles. Functions: 1) ensuring the divergence of chromosomes to the cell poles during mitosis or meiosis, 2) the center of organization of the cytoskeleton.
Organoids of movement
Not present in all cells. Organelles of movement include cilia (ciliates, epithelium respiratory tract), flagella (flagellates, sperm), pseudopods (rhizopods, leukocytes), myofibrils ( muscle cells) and etc.
Flagella and cilia- filament-shaped organelles, representing an axoneme bounded by a membrane. Axoneme is a cylindrical structure; the wall of the cylinder is formed by nine pairs of microtubules; in its center there are two single microtubules. At the base of the axoneme there are basal bodies, represented by two mutually perpendicular centrioles (each basal body consists of nine triplets of microtubules; there are no microtubules in its center). The length of the flagellum reaches 150 microns, the cilia are several times shorter.
Myofibrils consist of actin and myosin myofilaments that provide contraction of muscle cells.
Go to lectures No. 6“Eukaryotic cell: cytoplasm, cell membrane, structure and functions of cell membranes”
Unity of cell structure.
The contents of any cell are separated from the external environment by a special structure - plasma membrane (plasmalemma). This isolation allows you to create a very special environment inside the cell, unlike what surrounds it. Therefore, processes that do not occur anywhere else can occur in the cell; they are called life processes.
The internal environment of a living cell, bounded by the plasma membrane, is called cytoplasm. It includes hyaloplasm(basic transparent substance) and cell organelles, as well as various non-permanent structures - inclusions. Organelles that are present in any cell also include ribosomes, where it happens protein synthesis.
The structure of eukaryotic cells.
Eukaryotes- These are organisms whose cells have a nucleus. Core- this is the very organelle of the eukaryotic cell in which the hereditary information recorded in the chromosomes is stored and from which the hereditary information is transcribed. Chromosome is a DNA molecule integrated with proteins. The core contains nucleolus- the place where other important organelles involved in protein synthesis are formed - ribosomes. But ribosomes are only formed in the nucleus, and they work (i.e. synthesize protein) in the cytoplasm. Some of them are free in the cytoplasm, and some are attached to membranes, forming a network, which is called endoplasmic.
Ribosomes- non-membrane organelles.
Endoplasmic reticulum is a network of membrane-bounded tubules. There are two types: smooth and granular. Ribosomes are located on the membranes of the granular endoplasmic reticulum, so proteins are synthesized and transported there. And the smooth endoplasmic reticulum is the site of synthesis and transport of carbohydrates and lipids. There are no ribosomes on it.
The synthesis of proteins, carbohydrates and fats requires energy, which is produced in the eukaryotic cell by the “energy stations” of the cell - mitochondria.
Mitochondria- double-membrane organelles in which the process of cellular respiration occurs. Oxidizes on mitochondrial membranes organic compounds and chemical energy is accumulated in the form of special energy molecules (ATP).
There is also a place in the cell where organic compounds can accumulate and from where they can be transported - this is Golgi apparatus, system of flat membrane bags. It is involved in the transport of proteins, lipids, and carbohydrates. The Golgi apparatus also produces organelles for intracellular digestion - lysosomes.
Lysosomes- single-membrane organelles, characteristic of animal cells, contain enzymes that can break down proteins, carbohydrates, nucleic acids, and lipids.
A cell may contain organelles that do not have a membrane structure, such as ribosomes and a cytoskeleton.
Cytoskeleton- this is a musculoskeletal cell system, includes microfilaments, cilia, flagella, a cell center that produces microtubules and centrioles.
There are organelles that are characteristic only of plant cells, - plastids. There are: chloroplasts, chromoplasts and leucoplasts. The process of photosynthesis occurs in chloroplasts.
In plant cells also vacuoles- products cell activity, which are reservoirs of water and compounds dissolved in it. Eukaryotic organisms include plants, animals and fungi.
The structure of prokaryotic cells.
Prokaryotes - single-celled organisms, whose cells do not have a nucleus.
Prokaryotic cells are small in size and store genetic material in the form of a circular DNA molecule (nucleoid). Prokaryotic organisms include bacteria and cyanobacteria, which were formerly called blue-green algae.
If the process of aerobic respiration occurs in prokaryotes, then special protrusions are used for this plasma membrane - mesosomes. If bacteria are photosynthetic, then the process of photosynthesis occurs on photosynthetic membranes - thylakoids.
Protein synthesis in prokaryotes occurs at ribosomes. Prokaryotic cells have few organelles.
Hypotheses of the origin of organelles of eukaryotic cells.
Prokaryotic cells appeared on Earth earlier than eukaryotic cells.
1) symbiotic hypothesis explains the mechanism of emergence of some organelles of the eukaryotic cell - mitochondria and photosynthetic plastids.
2) Intussusception hypothesis- states that the origin of the eukaryotic cell comes from the fact that the ancestral form was an aerobic prokaryote. The organelles in it arose as a result of invagination and detachment of parts of the shell, followed by functional specialization into the nucleus, mitochondria, chloroplasts of other organelles.
There are only two types of organisms on Earth: eukaryotes and prokaryotes. They differ greatly in their structure, origin and evolutionary development, which will be discussed in detail below.
In contact with
Signs of a prokaryotic cell
Prokaryotes are also called prenuclear. A prokaryotic cell does not have other organelles that have a membrane membrane (endoplasmic reticulum, Golgi complex).
Also characteristic features for them are the following:
- without a shell and does not form bonds with proteins. Information is transmitted and read continuously.
- All prokaryotes are haploid organisms.
- Enzymes are located in a free state (diffusely).
- They have the ability to form spores under unfavorable conditions.
- The presence of plasmids - small extrachromosomal DNA molecules. Their function is the transfer of genetic information, increasing resistance to many aggressive factors.
- The presence of flagella and pili - external protein formations necessary for movement.
- Gas vacuoles are cavities. Due to them, the body is able to move in the water column.
- The cell wall of prokaryotes (namely bacteria) consists of murein.
- The main methods of obtaining energy in prokaryotes are chemo- and photosynthesis.
These include bacteria and archaea. Examples of prokaryotes: spirochetes, proteobacteria, cyanobacteria, crenarchaeotes.
Attention! Despite the fact that prokaryotes lack a nucleus, they have its equivalent - a nucleoid (a circular DNA molecule devoid of shells), and free DNA in the form of plasmids.
Structure of a prokaryotic cell
Bacteria
Representatives of this kingdom are among the most ancient inhabitants of the Earth and have a high survival rate in extreme conditions.
There are gram-positive and gram-negative bacteria. Their main difference lies in the structure of the cell membrane. Gram-positive have a thicker shell, up to 80% consists of a murein base, as well as polysaccharides and polypeptides. When stained according to Gram they give purple. Most of these bacteria are pathogens. Gram-negatives have a thinner wall, which is separated from the membrane by the periplasmic space. However, such a shell has increased strength and is much more resistant to the effects of antibodies.
Bacteria play a very important role in nature:
- Cyanobacteria (blue-green algae) help maintain required level oxygen in the atmosphere. They form more than half of all O2 on Earth.
- They promote the decomposition of organic remains, thereby taking part in the cycle of all substances, and participate in the formation of soil.
- Nitrogen fixers on legume roots.
- They purify water from waste, for example, from the metallurgical industry.
- They are part of the microflora of living organisms, helping to maximize the absorption of nutrients.
- Used in Food Industry for fermentation This is how cheeses, cottage cheese, alcohol, and dough are obtained.
Attention! Besides positive value bacteria also play a negative role. Many of them are fatal dangerous diseases such as cholera, typhoid fever, syphilis, tuberculosis.
Bacteria
Archaea
Previously, they were combined with bacteria into the single kingdom of Drobyanok. However, over time, it became clear that archaea have their own individual path of evolution and are very different from other microorganisms in their biochemical composition and metabolism. There are up to 5 types, the most studied are euryarchaeota and crenarchaeota. The features of archaea are:
- most of them are chemoautotrophs - they synthesize organic matter from carbon dioxide, sugar, ammonia, metal ions and hydrogen;
- play a key role in the nitrogen and carbon cycle;
- participate in digestion in humans and many ruminants;
- have a more stable and durable membrane shell due to the presence of ether bonds in glycerol-ether lipids. This allows archaea to live in highly alkaline or acidic environments, as well as high temperatures;
- the cell wall, unlike bacteria, does not contain peptidoglycan and consists of pseudomurein.
Structure of eukaryotes
Eukaryotes are a superkingdom of organisms whose cells contain a nucleus. Apart from archaea and bacteria, all living things on Earth are eukaryotes (for example, plants, protozoa, animals). Cells can vary greatly in their shape, structure, size and functions. Despite this, they are similar in the basics of life, metabolism, growth, development, ability to irritate and variability.
Eukaryotic cells can be hundreds or thousands of times larger than prokaryotic cells. They include the nucleus and cytoplasm with numerous membranous and non-membranous organelles. Membranous ones include: endoplasmic reticulum, lysosomes, Golgi complex, mitochondria,. Non-membrane: ribosomes, cell center, microtubules, microfilaments.
Structure of eukaryotes
Let's compare eukaryotic cells from different kingdoms.
The superkingdom of eukaryotes includes the following kingdoms:
- protozoa. Heterotrophs, some capable of photosynthesis (algae). They reproduce asexually, sexually and in a simple way into two parts. Most lack a cell wall;
- plants. They are producers; the main method of obtaining energy is photosynthesis. Most of plants are immobile and reproduce asexually, sexually and vegetatively. The cell wall is made of cellulose;
- mushrooms. Multicellular. There are lower and higher. They are heterotrophic organisms and cannot move independently. They reproduce asexually, sexually and vegetatively. They store glycogen and have a strong cell wall made of chitin;
- animals. There are 10 types: sponges, worms, arthropods, echinoderms, chordates and others. They are heterotrophic organisms. Capable of independent movement. The main storage substance is glycogen. The cell wall consists of chitin, just like in fungi. The main way reproduction - sexual.
Table: Comparative characteristics plant and animal cells
| Structure | plant cell | animal cell |
| Cell wall | Cellulose | Consists of the glycocalyx - a thin layer of proteins, carbohydrates and lipids. |
| Core location | Located closer to the wall | Located in the central part |
| Cell center | Exclusively in lower algae | Present |
| Vacuoles | Contains cell sap | Contractile and digestive. |
| Spare substance | Starch | Glycogen |
| Plastids | Three types: chloroplasts, chromoplasts, leucoplasts | None |
| Nutrition | Autotrophic | Heterotrophic |
Comparison of prokaryotes and eukaryotes
The structural features of prokaryotic and eukaryotic cells are significant, but one of the main differences concerns the storage of genetic material and the method of obtaining energy.
Prokaryotes and eukaryotes photosynthesize differently. In prokaryotes, this process takes place on membrane outgrowths (chromatophores), arranged in separate stacks. Bacteria do not have a fluorine photosystem, so they do not produce oxygen, unlike blue-green algae, which produce it during photolysis. The sources of hydrogen in prokaryotes are hydrogen sulfide, H2, various organic substances and water. The main pigments are bacteriochlorophyll (in bacteria), chlorophyll and phycobilins (in cyanobacteria).
Of all the eukaryotes, only plants are capable of photosynthesis. They have special formations - chloroplasts, containing membranes arranged in grana or lamellae. The presence of photosystem II allows the release of oxygen into the atmosphere during the process of photolysis of water. The only source of hydrogen molecules is water. The main pigment is chlorophyll, and phycobilins are present only in red algae.
Main differences and characteristic features Prokaryotes and eukaryotes are presented in the table below.
Table: Similarities and differences between prokaryotes and eukaryotes
| Comparison | Prokaryotes | Eukaryotes |
| Appearance time | More than 3.5 billion years | About 1.2 billion years |
| Cell sizes | Up to 10 microns | From 10 to 100 µm |
| Capsule | Eat. Performs a protective function. Associated with the cell wall | Absent |
| Plasma membrane | Eat | Eat |
| Cell wall | Composed of pectin or murein | Yes, except animals |
| Chromosomes | Instead there is circular DNA. Translation and transcription take place in the cytoplasm. | Linear DNA molecules. Translation takes place in the cytoplasm, and transcription in the nucleus. |
| Ribosomes | Small 70S-type. Located in the cytoplasm. | Large 80S-type, can attach to the endoplasmic reticulum and be located in plastids and mitochondria. |
| Membrane-enclosed organoid | None. There are membrane outgrowths - mesosomes | There are: mitochondria, Golgi complex, cell center, ER |
| Cytoplasm | Eat | Eat |
| None | Eat | |
| Vacuoles | Gas (aerosomes) | Eat |
| Chloroplasts | None. Photosynthesis takes place in bacteriochlorophylls | Present only in plants |
| Plasmids | Eat | None |
| Core | Absent | Eat |
| Microfilaments and microtubules. | None | Eat |
| Division methods | Constriction, budding, conjugation | Mitosis, meiosis |
| Interaction or contacts | None | Plasmodesmata, desmosomes or septa |
| Types of cell nutrition | Photoautotrophic, photoheterotrophic, chemoautotrophic, chemoheterotrophic | Phototrophic (in plants) endocytosis and phagocytosis (in others) |
Differences between prokaryotes and eukaryotes
Similarities and differences between prokaryotic and eukaryotic cells
Conclusion
Comparing a prokaryotic and eukaryotic organism is a rather labor-intensive process that requires consideration of many nuances. They have much in common with each other in terms of structure, ongoing processes and properties of all living things. The differences lie in the functions performed, methods of nutrition and internal organization. Anyone interested in this topic can use this information.
All living organisms, depending on the presence of a nucleus, can be divided into two large categories: prokaryotes and eukaryotes. Both of these terms originate from the Greek “karion” - core.
Those organisms that do not have a nucleus are called prokaryotes - prenuclear organisms with nuclear matter in the form of inclusions. The structure is somewhat different. Unlike prokaryotes, eukaryotes have a formed nucleus - this is their main difference. Prokaryotes include bacteria, cyanobacteria, rickettsia and other organisms. Representatives of Plants and Animals can be classified as eukaryotes.
The structure of various nuclear organisms is similar. Their main components are the nucleus and cytoplasm, which together make up the protoplast. Cytoplasm is a semi-liquid ground substance, or, as it is also called, hyaloplasm, which contains cellular structures- organelles that perform various functions. On the outside, the cytoplasm is surrounded by a plasma membrane. Plants have, in addition to the plasma membrane, a rigid cell membrane. The cytoplasm of fungi contains vacuoles - vesicles that are filled with water with various substances dissolved in it. In addition, the cell contains inclusions in the form of reserve nutrients or end products of metabolism. The structural features of a eukaryotic cell are determined by the functions of the inclusions found in the cell.
Structure and functions of a eukaryotic cell:
- The plasma membrane is a lipid bilayer with proteins embedded in it. The main function of the plasma membrane is the exchange of substances between the cell itself and environment. The plasma membrane also provides contact between two neighboring cells.
- core - this cellular element has a double membrane shell. The main one is the preservation of hereditary information - deoxyribonucleic acid. Thanks to the nucleus, cellular activity is regulated and genetic material is transferred to daughter cells.
- mitochondria - these organelles are present only in plant and animal cells. Mitochondria, like the nucleus, have two membranes, between which there are internal folds - cristae. Mitochondria contain circular DNA, ribosomes, and many enzymes. Thanks to these organelles, the oxygen stage of cell respiration is carried out (adenosine triphosphoric acid is synthesized).
- plastids - are found only in plant cells, since their main function is to carry out photosynthesis.
- (reticulum) is a whole system of flattened sacs - cisterns, cavities and tubes. Important organelles - ribosomes - are located on the endoplasmic reticulum (rough). In the tanks of the network, proteins are isolated and matured, which are also transported by the network itself. The synthesis of steroids and lipids occurs on the membranes of the smooth reticulum.
- Golgi complex - a system of flat single-membrane cisterns and vesicles attached to the expanded ends of the cisterns. The function of the Golgi complex is the accumulation and transformation of proteins and lipids. Secretory vesicles are also formed here, removing substances outside the cell. The structure of a eukaryotic cell is such that the cell has its own mechanism for excreting waste substances.
- lysosomes are single-membrane vesicles that contain hydrolytic enzymes. Thanks to lysosomes, the cell digests damaged organelles and dead organ cells.
- ribosomes - there are two types, but their main function is the assembly of protein molecules.
- Centrioles are a system of microtubules that are built from protein molecules. Thanks to centrioles, the internal skeleton of the cell is formed and it can maintain its constant shape.
The structure of a eukaryotic cell is more complex than that of a prokaryotic cell. Thanks to the presence of a nucleus, eukaryotes have the ability to transmit genetic information, thereby ensuring the constancy of their species.
A typical eukaryotic cell consists of three components - the membrane, the cytoplasm and the nucleus. The basis of the cell shell consists of plasmalemma (cell membrane) and carbohydrate-protein surface structure.
1. Plasmalemma .
2. Carbohydrate-protein surface structure. Animal cells have a small layer of protein (glycocalyx) . In plants, the surface structure of the cell is cell wall consists of cellulose (fiber).
Functions cell membrane: maintains cell shape and imparts mechanical strength, protects the cell, recognizes molecular signals, regulates metabolism between the cell and the environment, and carries out intercellular interaction.
Cytoplasm consists of hyaloplasm (the main substance of the cytoplasm), organelles and inclusions.
1. Hyaloplasma is a colloidal solution of organic and inorganic compounds, unites all cell structures into a single whole.
2. Mitochondria have two membranes: an outer smooth inner one with folds - cristae. Inside between the cristae is matrix, containing DNA molecules, small ribosomes and respiration enzymes. ATP synthesis occurs in mitochondria. Mitochondria divide by fission in two.
3. Plastids characteristic of plant cells. There are three types of plastids: chloroplasts, chromoplasts and leucoplasts. Divided by division in two.
I. Chloroplasts – green plastids in which photosynthesis occurs. The chloroplast has a double membrane. The chloroplast body consists of a colorless protein-lipid stroma, permeated by a system of flat sacs (thylakoids) formed by an internal membrane. Thylakoids form grana. The stroma contains ribosomes, starch grains, and DNA molecules.
II. Chromoplasts give different organs plants coloring.
III. Leukoplasts store nutrients. Chromoplasts and chloroplasts can be formed from leucoplasts.
4. Endoplasmic reticulum is a branched system of tubes, channels and cavities. There are non-granular (smooth) and granular (rough) EPS. The non-granular EPS contains enzymes of fat and carbohydrate metabolism (the synthesis of fats and carbohydrates occurs). The supragranular ER contains ribosomes that carry out protein biosynthesis. Functions of EPS: transport, concentration and release.
5. Golgi apparatus consists of flat membrane sacs and vesicles. In animal cells, the Golgi apparatus performs a secretory function; in plant cells, it is the center of polysaccharide synthesis.
6. Vacuoles filled with plant cell sap. Functions of vacuoles: storing nutrients and water, maintaining turgor pressure in the cell.
7. Lysosomes spherical in shape, formed by a membrane, inside which contains enzymes that hydrolyze proteins, nucleic acids, carbohydrates, and fats.
8. Cell center controls the processes of cell division.
9. Microtubules And microfilaments c form the cell skeleton.
10. Ribosomes eukaryotes are larger (80S).
11. Inclusions – reserve substances and secretions – only in plant cells.
Core consists of the nuclear membrane, karyoplasm, nucleoli, chromatin.
1. Nuclear envelope similar in structure cell membrane, contains pores. The nuclear membrane protects the genetic apparatus from the effects of cytoplasmic substances. Controls the transport of substances.
2. Karyoplasm is a colloidal solution containing proteins, carbohydrates, salts, and other organic and inorganic substances.
3. Nucleolus – spherical formation, contains various proteins, nucleoproteins, lipoproteins, phosphoproteins. The function of nucleoli is the synthesis of ribosome embryos.
4. Chromatin (chromosomes). In the steady state (time between divisions), DNA is evenly distributed in the karyoplasm in the form of chromatin. When dividing, chromatin is converted into chromosomes.
Functions of the nucleus: the nucleus contains information about the hereditary characteristics of the organism (informative function); chromosomes transmit the characteristics of an organism from parents to offspring (inheritance function); the nucleus coordinates and regulates processes in the cell (regulation function).
