There is a Golgi apparatus in prokaryotes or eukaryotes. Who are eukaryotes and prokaryotes: comparative characteristics of cells of different kingdoms

Plan

Introduction 2
Prokaryotic cell 4
Eukaryotic cell 6
Comparison of pro- and eukaryotic cells 13
Differences between eukaryotes and prokaryotes 14
List of used literature: 19

Introduction

A cell is an elementary unit of the structure and vital activity of all living organisms (except for viruses, which are often referred to as non-cellular forms of life), which has its own metabolism, capable of independent existence, self-reproduction and development. All living organisms, either, like multicellular animals, plants and fungi, consist of many cells, or, like many protozoa and bacteria, are single-celled organisms. The branch of biology dealing with the study of the structure and vital activity of cells is called cytology. Recently, it is also customary to talk about cell biology, or cell biology.
Discovery history
The first person to see the cells was the English scientist Robert Hooke (known to us thanks to Hooke's law). In 1665, trying to understand why the cork tree floats so well, Hooke began to examine thin sections of cork using a microscope he had improved. He discovered that the cork was divided into many tiny cells that reminded him of monastery cells, and he called these cells cells (in English cell means “cell, cell, cage”). In 1675, the Italian physician M. Malpighi, and in 1682 - the English botanist N. Gru, confirmed the cellular structure of plants. The cell began to be spoken of as a "bubble filled with nutritious juice." In 1674, the Dutch master Anthony van Leeuwenhoek (1632-1723) with the help of a microscope first saw in a drop of water “animals” - moving living organisms (ciliates, amoeba, bacteria). Also, Levenguk was the first to observe animal cells - erythrocytes and spermatozoa. Thus, already by the beginning of the 18th century, scientists knew that under high magnification, plants have a cellular structure, and they saw some organisms, which later were called unicellular. In 1802-1808, the French researcher Charles-Francois Mirbel established that all plants are composed of tissues formed by cells. JB Lamarck in 1809 extended Mirbel's idea of \u200b\u200bthe cellular structure to animal organisms. In 1825, the Czech scientist J. Purkine discovered the nucleus of the egg cell of birds, and in 1839 he coined the term "protoplasm". In 1831, the English botanist R. Brown first described the nucleus of a plant cell, and in 1833 he established that the nucleus is an indispensable organoid of a plant cell. Since then, the main thing in the organization of cells is not the membrane, but the content.
The cellular theory of the structure of organisms was formed in 1839 by the German zoologist T. Schwann and M. Schleiden and included three provisions. In 1858, Rudolf Virchow supplemented it with one more provision, but there were a number of mistakes in his ideas: for example, he assumed that the cells are weakly connected to each other and each exists "on its own." Only later was it possible to prove the integrity of the cellular system.
In 1878, the Russian scientist ID Chistyakov discovered mitosis in plant cells; in 1878 V. Flemming and P. I. Peremezhko discovered mitosis in animals. In 1882 W. Flemming observed meiosis in animal cells, and in 1888 E. Strasburger - in plant cells.
Cell structure
All cellular life forms on Earth can be divided into two kingdoms based on the structure of their constituent cells:
prokaryotes (prenuclear) are simpler in structure and arose earlier in the process of evolution;
eukaryotes (nuclear) - more complex, arose later. The cells that make up the human body are eukaryotic.
Despite the variety of forms, the organization of cells of all living organisms is subordinated to unified structural principles.
The contents of the cell are separated from the environment by the plasma membrane, or plasmalemma. Inside the cell is filled with cytoplasm, which contains various organelles and cellular inclusions, as well as genetic material in the form of a DNA molecule. Each of the organelles of the cell performs its own special function, and in the aggregate they all determine the vital activity of the cell as a whole.

Prokaryotic cell

Prokaryotes (from Latin pro - before, before and Greek ?????? - nucleus, nut) are organisms that, unlike eukaryotes, do not have a formed cell nucleus and other internal membrane organelles (with the exception of flat cisterns in photosynthetic species, for example, in cyanobacteria). The only large circular (in some species - linear) double-stranded DNA molecule, which contains the bulk of the cell's genetic material (the so-called nucleoid) does not form a complex with histone proteins (so-called chromatin). Prokaryotes include bacteria, including cyanobacteria (blue-green algae), and archaea. The descendants of prokaryotic cells are organelles of eukaryotic cells - mitochondria and plastids. The main content of the cell, filling its entire volume, is a viscous granular cytoplasm.
Prokaryotes (Latin Procaryota, from ancient Greek ??? "before" and ?????? "nucleus"), or prenuclear - unicellular living organisms that do not (unlike eukaryotes) have a formed cell nucleus and other internal membrane organelles (with the exception of flat cisterns in photosynthetic species, for example, in cyanobacteria). The only large circular (in some species - linear) double-stranded DNA molecule, which contains the bulk of the cell's genetic material (the so-called nucleoid) does not form a complex with histone proteins (so-called chromatin). Prokaryotes include bacteria, including cyanobacteria (blue-green algae), and archaea. The descendants of prokaryotic cells are organelles of eukaryotic cells - mitochondria and plastids.
Prokaryotes are divided into two taxa in the rank of domain (super kingdoms): Bacteria and Archaea.
Prokaryotic cells are characterized by the absence of a nuclear envelope; DNA is packed without the participation of histones. The type of nutrition is osmotrophic.
The genetic material of prokaryotes is represented by one DNA molecule, closed in a ring, there is only one replicon. The cells lack membrane-structured organelles. The genome may contain mobile genetic elements, and some prokaryotes (for example, Wolbachia) contain an unusually large number of them. The study of bacteria led to the discovery of horizontal gene transfer, which was described in Japan in 1959. This process is widespread among prokaryotes, as well as in some eukaryotes. The discovery of horizontal gene transfer in prokaryotes led to a different look at the evolution of life. Previously, evolutionary theory was based on the fact that species cannot exchange hereditary information. Prokaryotes can exchange genes with each other directly (conjugation, transformation) and also with the help of viruses - bacteriophages (transduction).

The structure of a typical prokaryotic cell: capsule, cell wall, plasmolemma, cytoplasm, ribosomes, plasmid, pili, flagellum, nucleoid.
Characteristics

Eukaryotic cell

Eukaryotes (eukaryotes) (from the Greek ?? - well, completely and ?????? - nucleus, nut) are organisms that, in contrast to prokaryotes, have a formed cell nucleus, delimited from the cytoplasm by a nuclear membrane. The genetic material is enclosed in several linear double-stranded DNA molecules (depending on the type of organisms, their number per nucleus can vary from two to several hundred), attached from the inside to the membrane of the cell nucleus and in the vast majority (except dinoflagellates) a complex with histone proteins, called chromatin. In eukaryotic cells, there is a system of internal membranes, which, in addition to the nucleus, form a number of other organelles (endoplasmic reticulum, Golgi apparatus, etc.). In addition, the overwhelming majority have permanent intracellular symbionts-prokaryotes - mitochondria, and in algae and plants - also plastids.
Eukaryotes, or Nuclear (lat. Eukaryota from the Greek. ?? - - good and ?????? - nucleus) is a domain (super-kingdom) of living organisms, whose cells contain nuclei. All organisms, except bacteria and archaea, are nuclear (viruses and viroids are also not eukaryotes, but not all biologists consider them to be living organisms).
Animals, plants, fungi, and groups of organisms under the general name protists are all eukaryotic organisms. They can be unicellular and multicellular, but they all have a common plan for the structure of cells. It is believed that all these such dissimilar organisms have a common origin, therefore the nuclear group is considered as a monophyletic taxon of the highest rank. According to the most widespread hypotheses, eukaryotes appeared 1.5–2 billion years ago. An important role in the evolution of eukaryotes was played by symbiogenesis - a symbiosis between a eukaryotic cell, which apparently already had a nucleus and is capable of phagocytosis, and bacteria swallowed by this cell - the precursors of mitochondria and plastids.

Endomembrane system and its components
The structure of the eukaryotic cell
Eukaryotic cells are on average much larger than prokaryotic cells, the difference in volume reaches thousands of times. Eukaryotic cells include about a dozen types of various structures known as organelles (or organelles, which, however, somewhat distorts the original meaning of this term), of which many are separated from the cytoplasm by one or more membranes (in prokaryotic cells, internal organelles surrounded by a membrane are rare ). The nucleus is a part of a cell, surrounded by a double membrane (two elementary membranes) in eukaryotes and containing genetic material: DNA molecules "packed" into chromosomes. The nucleus is usually one, but there are also multinucleated cells.

Schematic representation of an animal cell. (When you click on any of the names of the component parts of the cell, you will go to the corresponding article.)
Surface complex of an animal cell
Consists of the glycocalyx, the plasmalemma and the cortical layer of the cytoplasm located under it. The plasma membrane is also called the plasmalemma, the outer cell membrane. It is a biological membrane, about 10 nanometers thick. First of all, it provides a delimiting function in relation to the environment external to the cell. In addition, it performs a transport function. The cell does not spend energy to preserve the integrity of its membrane: the molecules are held according to the same principle by which fat molecules are held together - it is thermodynamically more advantageous for hydrophobic parts of molecules to be located in close proximity to each other. Glycocalyx is a molecule of oligosaccharides, polysaccharides, glycoproteins and glycolipids "anchored" in the plasma membrane. Glycocalyx performs receptor and marker functions. The plasma membrane of animal cells mainly consists of phospholipids and lipoproteins with embedded molecules of proteins, in particular, surface antigens and receptors. The cortical (adjacent to the plasma membrane) layer of the cytoplasm contains specific elements of the cytoskeleton - actin microfilaments ordered in a certain way. The main and most important function of the cortical layer (cortex) is pseudopodial reactions: ejection, attachment and contraction of pseudopodia. In this case, the microfilaments are rebuilt, lengthened or shortened. The shape of the cell also depends on the structure of the cytoskeleton of the cortical layer (for example, the presence of microvilli).
Cytoplasm structure
The liquid component of the cytoplasm is also called cytosol. Under a light microscope, it seemed that the cell was filled with something like a liquid plasma or sol, in which the nucleus and other organelles "float". In fact, this is not the case. The inner space of a eukaryotic cell is strictly ordered. The movement of organelles is coordinated with the help of specialized transport systems, the so-called microtubules, which serve as intracellular "roads" and special proteins dyneins and kinesins, which play the role of "engines". Individual protein molecules also do not diffuse freely throughout the intracellular space, but are directed to the necessary compartments using special signals on their surface, which are recognized by the cell transport systems.
Endoplasmic reticulum
In a eukaryotic cell, there is a system of membrane compartments (tubes and cisterns) passing into each other, which is called the endoplasmic reticulum (or the endoplasmic reticulum, EPR or EPS). That part of the EPR, to the membranes of which ribosomes are attached, is referred to as the granular (or rough) endoplasmic reticulum; proteins are synthesized on its membranes. Those compartments without ribosomes on their walls are referred to as agranular (or smooth) EPR, which takes part in lipid synthesis. The internal spaces of smooth and granular EPR are not isolated, but merge into each other and communicate with the lumen of the nuclear envelope.
Golgi apparatus
The Golgi apparatus is a stack of flat membrane cisterns, slightly expanded towards the edges. In the cisterns of the Golgi apparatus, some proteins synthesized on the membranes of granular ER and intended for secretion or formation of lysosomes mature. The Golgi apparatus is asymmetric - the cisterns located closer to the cell nucleus (cis-Golgi) contain the least mature proteins, membrane vesicles, vesicles budding from the endoplasmic reticulum, continuously join these cisterns. Apparently, with the help of the same vesicles, further movement of maturing proteins from one cistern to another occurs. Eventually, vesicles containing fully mature proteins bud from the opposite end of the organelle (trans-Golgi).
Nucleus
The cell nucleus contains DNA molecules on which the body's genetic information is recorded. In the nucleus, replication occurs - the doubling of DNA molecules, as well as transcription - the synthesis of RNA molecules on the DNA matrix. In the nucleus, the synthesized RNA molecules undergo some modifications (for example, insignificant, meaningless areas are excluded from the messenger RNA molecules during splicing), after which they enter the cytoplasm. The assembly of ribosomes also occurs in the nucleus, in special formations called the nucleoli. The compartment for the nucleus - the karyoteca - is formed due to the expansion and fusion of the endoplasmic reticulum cisterns with each other in such a way that the nucleus has double walls due to the narrow compartments of the nuclear envelope surrounding it. The cavity of the nuclear envelope is called the lumen or perinuclear space. The inner surface of the nuclear envelope is underlain by a nuclear lamina, a rigid protein structure formed by lamina proteins to which strands of chromosomal DNA are attached. In some places, the inner and outer membranes of the nuclear envelope merge and form the so-called nuclear pores, through which material exchange between the nucleus and the cytoplasm takes place.
Lysosomes
Lysosome is a small body, limited from the cytoplasm by a single membrane. It contains lytic enzymes that can break down all biopolymers. The main function is autolysis - that is, the splitting of individual organelles, sections of the cell cytoplasm.
Cytoskeleton
The elements of the cytoskeleton include protein fibrillar structures located in the cytoplasm of the cell: microtubules, actin and intermediate filaments. Microtubules take part in the transport of organelles, are part of the flagella, and the mitotic spindle of division is built from microtubules. Actin filaments are necessary to maintain the shape of the cell, pseudopodial reactions. The role of intermediate filaments also appears to be to maintain cell structure. Cytoskeleton proteins make up several tens of percent of the mass of cellular protein.
Centrioli
Centrioles are cylindrical protein structures located near the nucleus of animal cells (plants do not have centrioles). The centriole is a cylinder, the lateral surface of which is formed by nine sets of microtubules. The number of microtubules in a set can vary from 1 to 3 for different organisms.
Around the centrioles is the so-called center of organization of the cytoskeleton, the region in which the minus ends of the cell microtubules are grouped.
Before division, the cell contains two centrioles located at right angles to each other. During mitosis, they diverge to different ends of the cell, forming the poles of the division spindle. After cytokinesis, each daughter cell receives one centriole, which doubles for the next division. Doubling of centrioles occurs not by division, but by synthesizing a new structure perpendicular to the existing one.
The centrioles seem to be homologous to the basal bodies of flagella and cilia.
Mitochondria
Mitochondria are special cell organelles, the main function of which is the synthesis of ATP - a universal carrier of energy. Respiration (absorption of oxygen and release of carbon dioxide) also occurs due to the enzymatic systems of mitochondria.
The inner lumen of mitochondria, called the matrix, is delimited from the cytoplasm by two membranes, outer and inner, between which the intermembrane space is located. The inner mitochondrial membrane forms folds called cristae. The matrix contains various enzymes that are involved in respiration and ATP synthesis. The hydrogen potential of the inner mitochondrial membrane is of central importance for the synthesis of ATP.
Mitochondria have their own DNA genome and prokaryotic ribosomes, which certainly points to the symbiotic origin of these organelles. Not all mitochondrial proteins are encoded in the DNA of mitochondria, most of the genes of mitochondrial proteins are located in the nuclear genome, and the corresponding products are synthesized in the cytoplasm, and then transported to the mitochondria. Mitochondrial genomes differ in size: for example, the genome of human mitochondria contains only 13 genes. The simplest Reclinomonas americana has the largest number of mitochondrial genes (97) of the studied organisms.
Division into kingdoms
There are several options for dividing the eukaryotic super-kingdom into kingdoms. The kingdoms of plants and animals were identified first. Then the kingdom of mushrooms was isolated, which, due to biochemical characteristics, according to most biologists, cannot be attributed to any of these kingdoms. Also, some authors distinguish the kingdoms of protozoa, myxomycetes, chromists. Some systems have up to 20 kingdoms. According to the Thomas Cavalier-Smith system, all eukaryotes are subdivided into two monophyletic taxa - Unikonta and Bikonta.
Eukaryotic cell division
Amitosis is a direct cell division that occurs less frequently in eukaryotic somatic cells than mitosis. In most cases, amitosis is observed in cells with reduced mitotic activity: these are aging or pathologically altered cells, often doomed to death (cells of the embryonic membranes of mammals, tumor cells, and others). In amitosis, the interphase state of the nucleus is morphologically preserved, the nucleolus and nuclear envelope are clearly visible. There is no DNA replication. Spiralization of chromatin does not occur, chromosomes are not detected. The cell retains its inherent functional activity, which almost completely disappears during mitosis. Such, for example, is the division of macronuclei of many ciliates, where segregation of short fragments of chromosomes occurs without the formation of a spindle. In amitosis, only the nucleus divides, and without the formation of a fission spindle, so the hereditary material is distributed randomly. The absence of cytokinesis leads to the formation of binucleated cells, which are subsequently unable to enter the normal mitotic cycle. With repeated amitosis, multinucleated cells can form.
Mitosis (from the Greek ????? - thread) is an indirect cell division, the most common way of reproduction of eukaryotic cells, one of the fundamental processes of ontogenesis. Mitotic division ensures the growth of multicellular eukaryotes by increasing the population of tissue cells. The biological significance of mitosis lies in the strictly equal distribution of chromosomes between daughter nuclei, which ensures the formation of genetically identical daughter cells and maintains continuity in a number of cell generations. The fragmentation of the fertilized egg and the growth of most tissues in animals also occurs through mitotic divisions. Based on morphological features, mitosis is conventionally divided into:

The duration of mitosis is on average 1-2 hours. In animal cells, mitosis usually lasts 30-60 minutes, and in plant cells - 2-3 hours. For 70 years, human cells in total undergo about 1014 cell divisions.
Meiosis (from the Greek meiosis - decrease) or reduction cell division - division of the nucleus of a eukaryotic cell with a decrease in the number of chromosomes by half. It occurs in two stages (reduction and equational stages of meiosis). Meiosis should not be confused with gametogenesis - the formation of specialized germ cells or gametes from undifferentiated stem cells. A decrease in the number of chromosomes as a result of meiosis in the life cycle leads to a transition from the diploid phase to the haploid phase. The restoration of ploidy (the transition from the haploid phase to the diploid phase) occurs as a result of the sexual process. Due to the fact that in the prophase of the first, reduction, stage there is a pairwise fusion (conjugation) of homologous chromosomes, the correct course of meiosis is possible only in diploid cells or in even polyploids (tetra-, hexaploid, etc. cells). Meiosis can also occur in odd polyploids (tri-, pentaploid, etc. cells), but in them, due to the impossibility of ensuring pairwise fusion of chromosomes in prophase I, chromosome divergence occurs with disorders that threaten the viability of the cell or the developing from it a multicellular haploid organism. The same mechanism underlies the sterility of interspecific hybrids. Certain restrictions on the conjugation of chromosomes are also imposed by chromosomal mutations (large-scale deletions, duplications, inversions or translocations).
Division of prokaryotic cells
Prokaryotic cells divide in two. First, the cell is lengthened, a transverse septum is formed in it. At the final stage, the daughter cells diverge. A distinctive feature of prokaryotic cell division is the direct participation of the replicated DNA in the division process. Usually, prokaryotic cells divide to form two daughter cells of the same size, therefore this process is sometimes called binary division. Due to the fact that in the overwhelming majority of cases prokaryotic cells have a cell wall, binary division is accompanied by the formation of a septum - a septum between daughter cells, which then stratifies in the middle. The process of prokaryotic cell division has been studied in detail on the example of Escherichia coli.

Comparison of pro- and eukaryotic cells

The most important difference between eukaryotes and prokaryotes has long been considered the presence of a formed nucleus and membrane organelles. However, by the 1970s-1980s. it became clear that this is only a consequence of deeper differences in the organization of the cytoskeleton. For some time it was believed that the cytoskeleton is characteristic only of eukaryotes, but in the mid-1990s. proteins homologous to the main proteins of the eukaryotic cytoskeleton have also been found in bacteria.
It is the presence of a specifically arranged cytoskeleton that allows eukaryotes to create a system of mobile internal membrane organelles. In addition, the cytoskeleton allows endo- and exocytosis (it is assumed that it is thanks to endocytosis that intracellular symbionts, including mitochondria and plastids, appeared in eukaryotic cells). Another important function of the eukaryotic cytoskeleton is to ensure the division of the nucleus (mitosis and meiosis) and the body (cytotomy) of the eukaryotic cell (the division of prokaryotic cells is easier to organize). Differences in the structure of the cytoskeleton also explain other differences between pro and eukaryotes - for example, the constancy and simplicity of the forms of prokaryotic cells and a significant variety of shape and the ability to change it in eukaryotic, as well as the relatively large size of the latter. Thus, the size of prokaryotic cells is on average 0.5-5 microns, the size of eukaryotic cells is on average from 10 to 50 microns. In addition, only among eukaryotes there are truly giant cells, such as massive eggs of sharks or ostriches (in a bird's egg, the entire yolk is one huge egg), neurons of large mammals, whose processes, strengthened by the cytoskeleton, can reach tens of centimeters in length.

Differences between eukaryotes and prokaryotes

The most important, fundamental feature of eukaryotic cells is associated with the location of the genetic apparatus in the cell. The genetic apparatus of all eukaryotes is located in the nucleus and is protected by the nuclear envelope (in Greek “eukaryote” means having a nucleus). Eukaryotic DNA is linear (in prokaryotes, DNA is circular and is located in a special region of the cell - the nucleoid, which is not separated by a membrane from the rest of the cytoplasm). It is associated with histone proteins and other proteins in chromosomes that bacteria do not have.
In the life cycle of eukaryotes, there are usually two nuclear phases (haplophase and diplophase). The first phase is characterized by a haploid (single) set of chromosomes, then, merging, two haploid cells (or two nuclei) form a diploid cell (nucleus) containing a double (diploid) set of chromosomes. Sometimes during the next division, and more often after several divisions, the cell becomes haploid again. Such a life cycle and, in general, diploidy are not typical for prokaryotes.
The third, perhaps the most interesting difference, is the presence of special organelles in eukaryotic cells that have their own genetic apparatus, multiply by division and are surrounded by a membrane. These organelles are mitochondria and plastids. They are strikingly similar in structure and activity to bacteria. This circumstance prompted modern scientists to think that such organisms are the descendants of bacteria that have entered into a symbiotic relationship with eukaryotes. Prokaryotes are characterized by a small number of organelles, and none of them is surrounded by a double membrane. In prokaryotic cells, there is no endoplasmic reticulum, Golgi apparatus, lysosomes.
Another important difference between prokaryotes and eukaryotes is the presence of endocytosis in eukaryotes, including phagocytosis in many groups. Phagocytosis (literally "eating by the cell") refers to the ability of eukaryotic cells to capture, enclosing a membrane vesicle, and digest a variety of solid particles. This process provides an important protective function in the body. It was first discovered by I.I.Mechnikov at sea stars. The appearance of phagocytosis in eukaryotes is most likely associated with average sizes (further on the size differences are written in more detail). The size of prokaryotic cells is incommensurably smaller, and therefore, in the process of the evolutionary development of eukaryotes, they faced the problem of supplying the body with a large amount of food. As a result, the first real, mobile predators appear among eukaryotes.
Most bacteria have a cell wall that is different from the eukaryotic one (not all eukaryotes have one). In prokaryotes, this is a strong structure consisting mainly of murein (in archaea, of pseudomurein). The structure of murein is such that each cell is surrounded by a special mesh bag, which is one huge molecule. Among eukaryotes, many protists, fungi, and plants have a cell wall. In fungi, it consists of chitin and glucans, in lower plants, it consists of cellulose and glycoproteins, diatoms synthesize the cell wall from silicic acids, in higher plants it consists of cellulose, hemicellulose and pectin. Apparently, for larger eukaryotic cells, it became impossible to create a cell wall from one high-strength molecule. This circumstance could force eukaryotes to use a different material for the cell wall. Another explanation is that the common ancestor of eukaryotes, in connection with the transition to predation, lost the cell wall, and then the genes responsible for the synthesis of murein were also lost. When part of the eukaryotes returned to osmotrophic nutrition, the cell wall reappeared, but on a different biochemical basis.
The metabolism of bacteria is also diverse. In general, four types of food are distinguished, and all are found among bacteria. These are photoautotrophic, photoheterotrophic, chemoautotrophic, chemoheterotrophic (phototrophic use the energy of sunlight, chemotrophic use chemical energy). Eukaryotes either synthesize energy from sunlight themselves, or use ready-made energy of this origin. This may be due to the appearance of predators among eukaryotes, for which the need to synthesize energy has disappeared.
Another difference is the structure of the flagella. In bacteria, they are thin - only 15–20 nm in diameter. These are hollow filaments of flagellin protein. The structure of eukaryotic flagella is much more complex. They are a cell outgrowth surrounded by a membrane and contain a cytoskeleton (axoneme) of nine pairs of peripheral microtubules and two microtubules in the center. Unlike rotating prokaryotic flagella, eukaryotic flagella bend or wriggle.
The two groups of organisms under consideration, as has already been said, are also very different in their average size. The diameter of a prokaryotic cell is usually 0.5–10 µm, while the same indicator in eukaryotes is 10–100 µm. The volume of such a cell is 1000–10000 times larger than that of a prokaryotic one.
Ribosomes of prokaryotes are small (70S-type). Eukaryotic cells contain both larger 80S-type ribosomes located in the cytoplasm and 70s-prokaryotic-type ribosomes located in mitochondria and plastids.
Apparently, the time of the emergence of these groups also differs. The first prokaryotes arose in the process of evolution about 3.5 billion years ago, from which eukaryotic organisms evolved about 1.2 billion years ago.
Currently, prokaryotic (prenuclear) and eukaryotic (nuclear) cells are distinguished. Unlike prokaryotic, eukaryotic cell has a nucleus, limited by a membrane of two membranes and a large number of membrane organelles. Prokaryotes include blue-green algae, actinomycetes, bacteria, spirochetes, mycoplasmas, rickettsia and chlamydia; eukaryotes - most algae, fungi, lichens, plants and animals.

The main difference between prokaryotic and eukaryotic cells is that their DNA is not organized into chromosomes and is not surrounded by a nuclear envelope. Eukaryotic cells are much more complex. Their DNA, associated with a protein, is organized into chromosomes, which are located in a special formation, in fact, the largest cell organelle - the nucleus. In addition, the extra-nuclear active content of such a cell is
etc.................

All living organisms are subdivided into precellular and cellular. Viruses and phages are precellular. The second group, cellular, is divided into prokaryotes and eukaryotes, which are prenuclear and nuclear organisms.

Prokaryotes

The first cellular, prokaryotes, appeared on Earth more than 3 billion years ago. This was the greatest leap forward in life. Prokaryotes are bacteria. Their structure is relatively simple. Hereditary information, DNA, is in their primitive, low-protein ring chromosome. It is located in a special area of \u200b\u200bthe cytoplasm, a nucleoid, not separated from the rest of the cell by a membrane. The main thing that distinguishes prokaryotes and eukaryotes from each other is that in cells of the first type there is no real nucleus.

The cytoplasm of prenuclear cells has much fewer cellular structures. Of these, ribosomes are known that are smaller in comparison with the ribosomes of eukaryoid cells. The role of mitochondria in prokaryotes belongs to simple membrane structures. Chloroplast is also absent in them. Prokaryotes have a plasma membrane over which the cell membrane is located. They differ from eukaryotes in significantly smaller sizes. In some cases, in prokaryotes there may be so-called plasmids - small, in the form of a ring,

Eukaryotes

All nuclear cells differ in their general structural plan and common origin. They arose from prenuclear cells 1.2 billion years ago. Their structure is much more complicated. Both prokaryotes and eukaryotes have a cell membrane. But otherwise, their structural and biochemical features are very different. The most important difference is that nuclear cells have a true nucleus, which stores their genetic information.

The nucleus is delimited from the cytoplasm by a special membrane, consisting of the outer and inner layers. It is similar to the plasma membrane, but contains pores. Thanks to them, the exchange between the cytoplasm and the nucleus is carried out. The genome of a cell consists of a whole set of chromosomes; this is also how prokaryotes and eukaryotes differ from each other. The DNA in eukaryotic chromosomes is associated with histone proteins.

There are nucleoli in which ribosomes are formed. A structureless mass, karyoplasm, surrounds the chromosomes and nucleoli. Each species of animals and plants has its own, strictly defined set of chromosomes. When cells divide, they double and then are distributed among daughter cells

If we consider prokaryotes and eukaryotes, the differences are also visible in the cytoplasm of cells.

Plant cells are characterized by the presence of a large central vacuole and plastids. can move the nucleus to the periphery of the cell. The plant cell's nutrient reserve carbohydrate is starch. Outside, plant cells are covered with cellulose. There is no centriole in the cell center, which can only be seen in algae.

Animal cells do not have a central vacuole, plastids, and a dense cell membrane. There is a centriole in the center of the cell. The reserve carbohydrate in animal cells is glycogen.

Fungal cells do not always have centriole. The cell wall consists of chitin, there are no plastids in the cytoplasm, but there is a central vacuole in the center of the cell. Their carbohydrate reserve is also glycogen.

In the cytoplasm of eukaryotes, there are mitochondria, lysosomes, endoplasmic reticulum, organelles of movement. Their ribosomes are much larger than the ribosomes of prokaryotes. The cytoplasm of the cell is divided into separate sections, compartments, using special membranes consisting of lipids. Each of them has its own biochemical processes. It is almost never found in prokaryotes.

In general, prokaryotes and eukaryotes express the laws of evolution, which is characterized by a movement from simpler forms to more complex ones.

However, prenuclear cells are characterized by great plasticity and variety of metabolic processes. Many bacteria can receive energy through light or chemical reactions, and exist in an oxygen-deprived environment (anaerobic bacteria). Thanks to this, they fit into the picture of the modern world.

All living organisms on earth are made up of cells. There are two types of cells, depending on their organization: eukaryotes and prokaryotes.

Eukaryotes represent the kingdom of living organisms. Translated from the Greek language "eukaryote" means "owning the nucleus." Accordingly, these organisms in their composition have a nucleus in which all genetic information is encoded. These include mushrooms, plants and animals.

Prokaryotes - these are living organisms in whose cells the nucleus is absent. Bacteria and cyanobacteria are typical representatives of prokaryotes.

Time of occurrence

Prokaryotes were the first to emerge about 3.5 billion years ago, and after 2.4 billion years the development of eukaryotic cells began.

The size

Eukaryotes and prokaryotes differ greatly in size from each other. So the diameter of a eukaryotic cell is 0.01-0.1 mm, and a prokaryotic cell is 0.0005-0.01 mm. The volume of a eukaryote is about 10,000 times that of a prokaryote.

DNA

Prokaryotes have circular DNA that is located in the nucleoid. This cellular region is separated from the rest of the cytoplasm by a membrane. DNA has nothing to do with RNA and proteins, there are no chromosomes.

The DNA of eukaryotic cells is linear, located in the nucleus, which contains chromosomes.

Cell division of eukaryotes and prokaryotes

Prokaryotes reproduce mainly by simple division in half, while eukaryotes divide by mitosis, meiosis, or a combination of the two.

Organelles

Eukaryotic cells have organelles characterized by their own genetic apparatus: mitochondria and plastids. They are surrounded by a membrane and have the ability to reproduce through division.

Organelles are also found in prokaryotic cells, but in smaller numbers and not limited by the membrane.

Phagocytosis

Eukaryotes, unlike prokaryotes, have the ability to digest solid particles, enclosing them in a membrane vesicle. There is an opinion that this feature arose in response to the need to fully provide food for a cell many times larger than a prokaryotic one. The appearance of the first predators was a consequence of the presence of phagocytosis in eukaryotes.

Motor aids

Eukaryotic flagella have a rather complex structure. They are thin cell outgrowths surrounded by three membrane layers containing 9 pairs of microtubules at the periphery and two in the center. They have a thickness of up to 0.1 millimeters and are capable of bending along their entire length. In addition to flagella, eukaryotes are characterized by the presence of cilia. They are identical in structure to flagella, differing only in size. The length of the cilia is no more than 0.01 mm.

Some prokaryotes also have flagella, however, very thin, about 20 nanometers in diameter. They are passively rotating hollow protein filaments.

Conclusions site

Eukaryotes are basically multicellular organisms that reproduce by means of. Prokaryotes are unicellular and reproduce by dividing in two.
DNA of prokaryotes is freely located in the cytoplasm and has the shape of a ring. Eukaryotes have a nucleus where linear DNA is located.
The size of a eukaryotic cell is much larger than the size of a prokaryotic one, while eukaryotes are characterized by the presence of phagocytosis, which contributes to sufficient nutrition of the cell.

1. Prokaryotes lack membranes that limit the organelles of the bacterial cell (nucleus, mitochondria, ribosomes) from the cytoplasm. Of the membranes, only the cytoplasmic membrane is present.

2. The nucleus of prokaryotes (nucleoid) of fibrial structure, the nuclear envelope is absent.

3. Prokaryotes lack mitochondria, chloroplasts, KG. EPS.

4. Redox fragments are localized in mesosomes (derivatives of the cytoplasmic membrane)

5. Prokaryotes do not have mitosis, they multiply by binary fission.

6. Prokaryotes have a haploid genome.

7. There is no cell center

8. Intracellular movements of the cytoplasm and amoeboid movement are not typical for prokaryotes.

Specific traits of M / O

1. Small size, weight, volume and relative simplicity of structure.

2. Extremely high breeding rates

3. A wide variety of ways to obtain energy and through metabolism, a wide range of end products of metabolism.

4. Ability to biodegrade almost all natural and artificial substances.

5. Extremely high degree of adaptation as a result of high rates of variability.

6. Mass population and ubiquity.

6. Structure and function of bacterial cell surface formations. Capsule. Detection methods.

The bacterial cell is surrounded by an outer shell (Fig. 3.2), which consists of a capsule, a capsule-like shell, and a cell wall. The ability of the cell to perceive aniline dyes (tinctorial properties) depends on their composition. Capsules, depending on the severity, are divided into micro- and macrocapsules. The former are found only during electron microscopic examination in the form of microfibrils of mucopolysaccharides, which are closely adjacent to the cell wall. Macrocapsules are a pronounced mucous layer that covers the outside of the cell wall. It consists of polysaccharides and rarely polypeptides (for example, in anthrax bacteria). As a rule, a few types of pathogenic bacteria (pneumococci, etc.) form a macrocapsule under unfavorable environmental conditions, for example, in the body of animals or humans. However, in some species (Klebsiella pneumoniae), the macrocapsule is constantly found.

The capsule-like shell is a lipid-polysaccharide formation, relatively loosely bound to the cell surface, as a result of which, unlike a capsule, it can be released into the environment.

The capsule or capsule-like shell can be coated with exopolysaccharides, which are formed from environmental carbohydrates by the action of bacterial enzymes. At the same time, glucans and levans ensure the adhesion of bacteria to different surfaces, often smooth.

The capsule has various functions:

1. Protective, protecting the cell from adverse environmental conditions,

2. adhesive, promoting "adhesion" to the surface (receptors) of the host cell.

3. Often pathogenic and antigenic properties. Non-pathogenic bacteria can also form a macrocapsule, which apparently performs only a protective function.

7. The structure and function of the cell wall of gram-positive and gram-negative bacteria. Forms of bacteria with cell wall defects.

Cell wall (CS) -bioheteropolymer of complex chemical composition, covering the entire surface of a prokaryotic cell.

The basis of the cell wall is peptidoglycan, which provides the rigidity and elasticity of the CS. The structure of peptidoglycan parallel polysaccharide (glycan) chains consisting of alternating links [\\ "- acetyl1 lnjozamineand N-acetylmuramic acidA tripeptide is covalently linked to each residue of N-acetidmuramic acid

Differences between Gram + and Gram-bacteria.

Group	1 "rumm - * -_ ^ ____________________	Gram -
Gram stain	purple	pink
CS thickness	20-60 nm	10-20 nm
% lipid content	1,6%	22,6%
The structure of peptidoglycan	Peptides of peptidoglycans are linked through a peptidyl bridge of 5, glycine residues	Acetylmuramic acids of each glycan chain are linked through two tetrapeptides of the same type
% peptidoglycan content	40-90% Multi-layer	5-10% Single layer
The presence of teichoic acids	There are	Absent
The peculiarity of the release of enzymes	Enzymes are released inconsistently into the environment	Enzymes are released into the periplasmic space between the CS and CM
Representatives	All disease-causing cocci, except for gonococcus and meningococcus, bacillus, iclostrpdia	Enterobacteriaceae, vibrios, treponema

KS functions:

1. Gives the cell a certain shape.

2. Protects it from environmental influences

3. It carries a variety of receptors on the surface, to which some phages, colysines and chemical compounds attach.

4. Through the CS, nutrients enter the cell and metabolic products are released

5. Suppresses high intracellular osmotic pressure.

KS gram-bact. represented by a three-layer outer membrane (peptidoglycan + lipopolysaccharide + lipoproteins). Some proteins (norins), penetrating the outer membrane, form pores through which hydrophilic substances with low molecular weight pass.

Peptidoglycan is the target of some antibiotics (penicillin) and enzymes (lysozyme). Penicillin disrupts the formation of tetrapeptide bonds, lysozyme destroys glycosidic bonds between muramic acid and acetylglucosamine.

With the action of penicillin on the growing tank. culture is formed shellless formsbacteria:

1 Protoplasts are completely devoid of CS.

2.Spheroplasts - partially devoid of CS

Both protoplasts and spheroplasts undergo plasmolysis in an isotonic environment, but in a psheryunic environment they show weak metabolic activity! lose the ability to reproduce.

3.L-forms - completely or partially devoid of KS, retain the ability to reproduce.

a) stable - capable of reversion to the original form.

b) unstable - not capable of reversion

8. Cytoplasmic structures of bacteria, functions, methods of detection. Acid-resistant microbes. Painting method.

Flagella... Flagella are located on the surface of a number of bacterial cells (Fig. 3.5). They include the flagelin protein, which in its structure belongs to the contractile proteins of the Myosin type. Flagella are attached to the basal body, which consists of a system of several discs mounted in the cytoplasmic membrane and CS. The number and location of flagella in different bacteria is not the same.

Monotrichs have only one flagellum at one of the cell poles,

lofotrichi - a bunch of flagella,

amphitrichs - flagella are located at both poles of the cell,

peritrichus - Over its entire surface.

Flagella have antigenic properties.

Drank- thin hollow filaments of a protein nature, 0.3–10 µm in length, 10 nm thick, covering the surface of bacterial cells. Unlike flagella, they do not perform a locomotor function. By their functional purpose, they are divided into several types.

Drank 1 general type cause the attachment or adhesion of bacteria to certain cells of the host organism. Their number is large - from several hundred to several thousand per one bacterial cell. Adhesion is the initial stage of any infectious process.

Drank 2 types (synonym: conjugative, or sex, drank - sex pili)participate in the conjugation of bacteria, which ensures the transfer of a part of the genetic material from the donor cell to the recipient cell. They are available only in donor bacteria in a limited amount (1-4 per cell).

Cytoplasmic membrane (CM) is a vital structural component of a bacterial cell. It restricts the protoplast to just below the cell wall. Chemically, CM is a lipoprotein consisting of 15-30% lipids and 50-70% proteins. In addition, it contains about 2-5% carbohydrates and a small amount of RNA. The composition of membrane lipids consists mainly of neutral lipids and phospholipids. Some bacteria have glycolipids, and mycoplasmas have sterols.

The lipid composition of membranes is not constant in terms of quality and quantity. In the same type of bacteria, it changes depending on the conditions of its cultivation on a nutrient medium and the age of the culture. Different types of bacteria differ from each other in the lipid composition of their membranes.

Membrane proteins are divided into structural and functional. The latter include enzymes involved in the biosynthesis of various components of the CM, which occurs on the surface of the CM, as well as redox enzymes, permeases, etc.

CM is a complexly organized structure consisting of three layers, which are revealed during electron microscopic examination. The double phospholipid layer is permeated with globulins, which provide the transport of substances into the bacterial cell.

CMs perform vital functions,violation of which leads to the death of the bacterial cell. These include, first of all, the regulation of the entry of metabolites and ions into the cell, participation

in metabolism, DNA replication, and in a number of bacteria in sporulation, etc.

Mesosomes are derivatives of CM. They have a different structure in different bacteria, located in different parts of the cell, either in the form of concentric membranes, or bubbles, tubules, or in the form of a loop, which is characteristic mainly of gram-negative bacteria. Mesosomes are associated with a nucleoid. They are involved in cell division and sporulation.

The cytoplasm in prokaryotes, as well as in eukaryotes, is a complex colloid system consisting of water (about 75%), mineral compounds, proteins, RNA and DNA, which are part of nucleoid organelles, ribosomes, mesosomes, inclusions.

Nucleoid is the equivalent of the eukaryotic nucleus, although it differs from it in its structure and chemical composition. It is devoid of a nuclear membrane, does not contain chromosomes, and does not divide by mitosis. The nucleoid lacks the main proteins - histones. The only exceptions are some bacteria. It contains a double-stranded DNA molecule, as well as small amounts of RNA and proteins. A DNA molecule with a molecular weight of (2-3) x 10 9 is a closed ring structure in which all the hereditary information of the cell is encoded, i.e. the genome of the cell. By analogy with eukaryotic chromosomes, bacterial DNA is often referred to as a chromosome. It should be remembered that it is presented in the cell in the singular, since bacteria are haploid. However, before cell division, the number of nucleoids doubles, and during division it increases to 4 or more.

All organisms that have a cellular structure belong to one of the groups (super kingdoms) - prokaryotes (pre-nuclear) or eukaryotes (nuclear).

TO eukaryotes include the kingdoms of mushrooms, plants and animals. Translated from Greek, the word "eukaryote" means "owning the nucleus," that is, all eukaryotes have a nucleus. Eukaryotic cells are generally similar in structure. Although there are noticeable differences between the cells of organisms that belong to different kingdoms of living nature. for instance , plant cells have various plastids and a large central vacuole, which sometimes pushes the nucleus to the periphery. In fungal cells, the wall usually consists of chitin, and plastids are absent. In animal cells, there are no plastids, no dense wall, no central vacuole.

In addition to fairly large ribosomes, eukaryotes also have many other organelles: EPS, mitochondria, cell center, plastids, etc.

Cells prokaryote have relatively simple structure... They don't an organized nucleus, and a single chromosome is not separated by a membrane from the rest of the cell, but lies directly in the cytoplasm. However, this chromosome contains all the hereditary information of the cell. Prokaryotes include bacteria, cyanobacteria, and archaea.

Cytoplasm of prokaryotes very poor in structure. It contains numerous small ribosomes. The functional role of chloroplasts and mitochondria is played by special membrane folds.

The cells of eukaryotes and prokaryotes themselves are very different. and in size... A eukaryotic cell is 1000 times larger than a prokaryotic cell in volume and 10 times in diameter. The diameter of a eukaryotic cell is 0.01-0.1 mm, and that of a prokaryotic cell is 0.0005-0.01 mm.

Eukaryotes and prokaryotes differ in genetic apparatus... Thus, the genetic apparatus of a eukaryotic cell is located in the nucleus and is protected by a membrane. Eukaryotic DNA is linear, in a 50/50 ratio is linked to proteins. They form a chromosome. Unlike eukaryotes, DNA in prokaryotes is circular, naked (almost not connected to proteins), lies in a special region of the cytoplasm - the nucleoid and is separated from the rest of the cytoplasm by means of a membrane.

Eukaryotic cell is divided by mitosis, meiosis, or a combination of these methods. The life cycle of eukaryotes consists of two nuclear phases. The first (haplophase) is distinguished by a single set of chromosomes. In the second phase (diplophase), two haploid cells merge to form a diploid cell, which contains a double set of chromosomes. After several divisions, the cell becomes haploid again.

This life cycle is not typical for prokaryotes. Basically, prokaryotes reproduce by simple division.

Eukaryotes, unlike prokaryotes, can digest particulate matter by enclosing them in a membrane vesicle. It is believed that the appearance of the first predators in eukaryotes was a consequence of this process (phagocytosis).

Eukaryotes are different from prokaryotes and the presence of motor devices... Eukaryotes have flagella that are complex in structure. Flagella are thin cellular outgrowths that are surrounded by three layers of membrane. These outgrowths contain nine pairs of microtubules along the periphery and two in the center. Flagella are up to 0.1 mm thick and can bend. Also, in addition to flagella, eukaryotes have cilia. The cilia and flagella are identical in structure and differ only in size. The length of the cilia reaches no more than 0.01 mm.

Some prokaryotes are also characterized by the presence of flagella, the thickness of which is very small and is about 20 nanometers in diameter. Prokaryotic flagella are passively rotating hollow protein filaments.

It is believed that prokaryotes were the first to appear about 3.5 billion years ago, which after 2.4 billion years began the emergence of eukaryotic cells.

So:

Eukaryotes include fungi, plants, and animals, while prokaryotes include bacteria, cyanobacteria, and archaea.
Eukaryotes of any kingdom have a nucleus. It is in the nucleus that the genetic apparatus of eukaryotes is located, protected by a special membrane. Prokaryotes have no nucleus.
Prokaryotic cells have a simple structure, and the only chromosome with all hereditary information lies simply in the cytoplasm, in contrast to the eukaryotic cell, which is much more complex and diverse.
The cytoplasm of prokaryotes is poor in composition and has many small ribosomes. Eukaryotes have large ribosomes and many other organelles. The cell itself is 1000 times larger than a prokaryotic cell in volume, and 10 times in diameter.
Eukaryotic DNA is linear, half connected to proteins and a chromosome is formed in it. In prokaryotes, DNA is circular, naked and lies in the nucleoid - a special region of the cytoplasm.
Eukaryotes mainly reproduce through mitosis and meiosis or a combination of both, while prokaryotes reproduce by dividing the cell in two.