Why are bacteria classified as a special kingdom of living nature? Real bacteria. Archaebacteria. Oxyphotobacteria The kingdom of bacteria includes living organisms

First question The kingdom of bacteria unites living organisms that have common characteristics: 1 Consist of... (one or many) cells 2 in the cell... (is present or absent) a clearly defined nucleus 3 Very small organisms, visible... (to the naked eye) eye or only with a microscope) 4 Found... (in all or only some) habitats Second question They are able to live both in the presence of oxygen (.... bacteria) and in an oxygen-free environment (.... .bacteria) Third question In industry, bacteria are used to produce fermented milk products, for example..... . Fourth question: Most bacteria are heterotrophs, that is, they are used for nutrition... . Among them there are saprotrophs that use... ; Bacteria settle in living organisms -... Question Five Bacteria multiply by... . The high rate of bacterial reproduction is especially dangerous in the case of the proliferation of pathogenic bacteria, for example... . Sixth question Knowing about the existence of (invisible bacteria), it is important to follow the rules of hygiene: ... . I give 60 points

Real bacteria. Archaebacteria. Oxyphotobacteria

OPTION 1

For each task, choose one correct answer from the four proposed.

A1. All bacteria inhabiting planet Earth are united in the kingdom

1) Prokaryotes

3) Plants

4) Animals

A2. They do not have a formal core

2) plants

3) bacteria

4) animals

AZ. The bacterial flagellum is an organelle for

1) movement

2) protein storage

3) reproduction

4) enduring unfavorable conditions

A4. Bacterial spores serve to

1) power supply

2) breathing

3) reproduction

4) enduring unfavorable conditions

A5. Organisms that feed on prepared organic substances are called

2) autotrophs

3) anaerobes

4) heterotrophs

A6. Organisms that absorb oxygen during respiration are called

1) aerobes

2) anaerobes

3) autotrophs

4) heterotrophs

A7. Bacteria convert the remains of dead bodies of organisms into inorganic substances.

1) destroyers

2) symbionts

3) nodule

4) pathogenic

A8*. The feeding method of most cyanobacteria is

1) photosynthesis

2) fermentation

4) rotting

A9*. Methane-producing bacteria live in

1) swamps

2) salt lakes

3) plant roots

4) spring water

B1.

A. Chemosynthesis is the process of formation of organic substances using the energy of inorganic compounds.

B. Kefir is produced using fermentation bacteria.

1) Only A is correct

2) Only B is correct

3) Both judgments are correct

4) Both judgments are incorrect

B2. Choose three true statements. The bacterial cell contains

1) Formed core

2) Chloroplast

3) Cytoplasm

4) Outer membrane

5) Mitochondria

6) Flagellum

B3. Establish a correspondence between the nutritional feature and the ecological group of bacteria.

FOOD FEATURE

A. They feed on the juices of living organisms, causing them harm

B. They themselves form organic substances using the energy of sunlight

B. Carry out the transformation of organic substances of dead bodies into inorganic compounds

ECOLOGICAL GROUP OF BACTERIA

1) Destroyers

3) Autotrophs

IN 1.

Organisms that themselves produce organic substances belong to the group ... (A), and organisms that absorb ready-made organic substances are ... (B). Of these, plant organisms in which sunlight is the primary source of energy are called ... (B).

Vocabulary: 1. Phototrophs, 2. Autotrophs, 3. Heterotrophs

Answer: A-2, B-3, C-1

OPTION 2

A1. The most ancient inhabitants of our planet -

2) Plants

3) Bacteria

4) Animals

A2. The hereditary material of the cell is not separated from the cytoplasm in

2) Plants

3) Bacteria

4) Animals

AZ. Separates the bacterial cell from the environment

1) cytoplasm

3) nuclear membrane

4) outer membrane

A4. Bacterial cells multiply

1) disputes

2) flagella

3) areas of the cytoplasm

4) cell division

A5. Organisms that are able to synthesize organic substances from inorganic compounds are called

2) anaerobes

3) autotrophs

4) heterotrophs

A6. Organisms that exist in an oxygen-free environment are called

2) anaerobes

3) autotrophs

4) heterotrophs

A7. Bacteria that interact with other organisms for mutual benefit are called

1) destroyers

2) symbionts

3) pathogenic

A8*. The mutually beneficial relationship between cyanobacteria and fungi is called

1) symbiosis

3) predation

4) competition

A9*. Halobacteria live in

1) swamps

2) salt lakes

3) plant roots

4) fresh water bodies

B1. Are the following statements true?

A. Photosynthesis is the process of formation of organic substances using the energy of sunlight.

B. Pathogenic bacteria affect only the human body and are not found in the body of plants and animals.

1) Only A is correct

3) Only B is correct

4) Both judgments are correct

5) Both judgments are incorrect

B2. Choose three true statements.

Bacteria carry out life processes

1) cell division in half

2) propagation by seeds

3) breathing

4) tissue formation

5) food

6) formation of organs

BZ. Establish a correspondence between the feeding habits of bacteria and the feeding method.

FEATURES OF BACTERIA NUTRITION

A. They live in the bodies of other organisms and benefit them

B. Eat other bacteria

B. They themselves form organic substances using the energy of inorganic compounds

METHOD OF NUTRITION

1) Autotrophic

2) Symbiosis

3) Predation

Write down the corresponding numbers in the table.

IN 1. Read the text. Fill in the gaps with the numbers that represent the words from the dictionary.

The contents of the bacterial cell limit... (A). In a prokaryotic cell there is no... (B). Bacteria that absorb oxygen during respiration are called... (B), and those that use other substances for oxidation are... (D).

Vocabulary: 1. Anaerobes. 2. Plasma membrane. 3. Aerobes. 4. Nuclear envelope.

Answer: A-2, B-4, C-3, D-1

Test yourself by completing the suggested tasks (at the teacher's discretion - in class or at home).

1. Life on the modern planet is diverse and represented by several kingdoms.

Answer: plants, animals, fungi, bacteria.

2. The kingdom of bacteria unites living organisms that have common characteristics: they consist of

Answer: one cell

- in a cage

Answer: there is no clearly defined core

- very small organisms, visible

Answer: only through a microscope

- meet

Answer: in all habitats

3. Bacteria have all the signs of life. They breathe

Answer: they feed, excrete the products of their vital activity, i.e. carry out metabolism, reproduce, adapt to environmental conditions.

4. They are able to live in the presence of oxygen

Answer: bacteria - aerobes,

and in an oxygen-free environment

Answer: bacteria are anaerobes

5. Even in everyday life, it is important for a person to know about the existence of anaerobic bacteria, since

Answer: the absence of atmospheric oxygen is a favorable environment for their development. Anaerobe bacteria are dangerous to humans, so preserving a jar of mushrooms at home can result in poisoning.

6. In industry, bacteria are used to produce fermented milk products, for example

Answer: kefir, sour cream, cheeses.

7. Most bacteria are heterotrophs, i.e. used for nutrition

Answer: ready-made organic substances.

Among them there are saprotrophs that use

Answer: organic matter from dead bodies; Bacteria inhabit living organisms

8. In the process of metabolism, bacteria not only consume ready-made organic substances, but also release waste products into the environment. This feature of bacteria is used in biotechnology, producing

Answer: antibiotics, vitamins, proteins.

9. Bacteria multiply by

Answer: cell division into two parts. The high rate of bacterial reproduction is especially dangerous in the case of the proliferation of pathogenic bacteria, for example Answer: dysentery bacteria.

10. Knowing about the existence of “invisible bacteria”, it is important to follow the rules of hygiene

Answer: wash your hands and body, brush your teeth, keep your clothes clean, do not drink water from untested sources, fight flies, wear gloves when working in the garden, cover your coughs and sneezes with a tissue.

11. In case of simple injuries, it is necessary to know first aid techniques. Test yourself by naming these techniques.

Answer: the wound on the body must be treated with hydrogen peroxide and bandaged.

12. Having mastered all habitats, bacteria play a large role in the life of the modern planet.

Answer: They convert organic matter from fallen leaves, dying plants, and dead animals into minerals and return them to the soil solution, participating in the cycle of substances.

Biology test Kingdom of Prokaryotes for 7th grade students with answers. The test includes 2 options, each option consists of 3 parts (Part A, Part B, Part C). Part A has 9 tasks, Part B has 3 tasks, Part C has 1 task.

1 option

A1. All bacteria inhabiting planet Earth are united in the kingdom

1) Prokaryotes
2) Mushrooms
3) Plants
4) Animals

A2. Formed core Not have

1) mushrooms
2) plants
3) bacteria
4) animals

A3. The bacterial flagellum is an organelle for

1) movement
2) protein storage
3) reproduction

A4. Bacterial spores serve to

1) power supply
2) breathing
3) reproduction
4) enduring unfavorable conditions

A5. Organisms that feed on prepared organic substances are called

1) aerobes
2) anaerobes
3) autotrophs
4) heterotrophs

A6. Organisms that absorb oxygen during respiration are called

1) aerobes
2) anaerobes
3) autotrophs
4) heterotrophs

A7. Bacteria convert the remains of dead bodies of organisms into inorganic substances.

1) destroyers
2) symbionts
3) nodule
4) pathogenic

A8. The feeding method of most cyanobacteria is

A9. Methane-producing bacteria live in

1) swamps
2) salt lakes
3) plant roots
4) spring water

B1.

A. Chemosynthesis is the process of formation of organic substances using the energy of inorganic compounds.
B. Kefir is produced using fermentation bacteria.

1) Only A is correct
2) Only B is correct
3) Both judgments are correct
4) Both judgments are incorrect

B2.

The bacterial cell contains

1) decorated core
2) chloroplast
3) cytoplasm
4) outer membrane
5) mitochondria
6) flagellum

B3. Establish a correspondence between the nutritional feature and the ecological group of bacteria.

Nutrition feature

A. They feed on the juices of living organisms, causing them harm
B. They themselves form organic substances using the energy of sunlight
B. Carry out the transformation of organic substances of dead bodies into inorganic compounds

Ecological group of bacteria

B1.

Organisms that themselves produce organic substances belong to the group ... (A), and organisms that absorb ready-made organic substances are ... (B). Of these, plant organisms in which sunlight is the primary source of energy are called ... (B).

1. Phototrophs.
2. Autotrophs.
3. Heterotrophs.

Option 2

A1. The most ancient inhabitants of our planet -

1) mushrooms
2) plants
3) bacteria
4) animals

A2. Hereditary material of the cell Not separated from the cytoplasm

1) mushrooms
2) plants
3) bacteria
4) animals

A3. Separates the bacterial cell from the environment

1) cytoplasm
2) flagellum
3) nuclear membrane
4) outer membrane

A4. Bacterial cells multiply

1) disputes
2) flagella
3) areas of the cytoplasm
4) cell division

A5. Organisms that are able to synthesize organic substances from inorganic compounds are called

1) aerobes
2) anaerobes
3) autotrophs
4) heterotrophs

A6. Organisms that exist in an oxygen-free environment are called

1) aerobes
2) anaerobes
3) autotrophs
4) heterotrophs

A7. Bacteria that interact with other organisms for mutual benefit are called

1) destroyers
2) symbionts
3) pathogenic
4) predatory

A8. The mutually beneficial relationship between cyanobacteria and fungi is called

A9. Halobacteria live in

1) swamps
2) salt lakes
3) plant roots
4) fresh water bodies

B1. Are the following statements true?

A. Photosynthesis is the process of formation of organic substances using the energy of sunlight.
B. Pathogenic bacteria affect only the human body and are not found in the body of plants and animals.

1) Only A is correct
3) Only B is correct
4) Both judgments are correct
5) Both judgments are incorrect

B2. Choose three true statements.

Bacteria carry out life processes

1) cell division in half
2) propagation by seeds
3) breathing
4) tissue formation
5) food
6) formation of organs

B3. Establish a correspondence between the feeding habits of bacteria and the feeding method.

Features of bacterial nutrition

A. They live in the bodies of other organisms and benefit them
B. Eat other bacteria
B. They themselves form organic substances using the energy of inorganic compounds

Nutrition method

1. Autotrophic
2. Symbiosis
3. Predation

IN 1. Read the text. Fill in the blanks with the numbers that represent the words below.

The contents of the bacterial cell are limited by... (A). In a prokaryotic cell there is no... (B). Bacteria that absorb oxygen during respiration are called ... (B), and those that use other substances for oxidation are ... (D).

1. Anaerobes.
2. Plasma membrane.
3. Aerobes.
4. Nuclear envelope.

Answers to the biology test Kingdom of Prokaryotes
1 option
A1-1
A2-3
A3-1
A4-4
A5-4
A6-1
A7-1
A8-1
A9-1
B1-3
B2-346
B3-231
B1-231
Option 2
A1-3
A2-3
A3-4
A4-4
A5-3
A6-2
A7-2
A8-1
A9-2
B1-1
B2-134
B3-231
B1-2431

Major kingdoms of living organisms

Science deals with the classification of living organisms.taxonomy . Usually in scientific literature all living organisms are divided into two empires -empire non-cellular , orviruses , Andempire cellular .

Viruses

Cellular organisms

superkingdom eukaryotes , ornuclear having a formed nucleus, separated from the cytoplasm by a nuclear envelope;

superkingdom of prokaryotes , orpre-nuclear , which do not have a nuclear membrane (see Fig. 1).

Rice. 1. Classification of living organisms

Prokaryotes are very small, single-celled organisms without a nucleus. Among them we can distinguish the kingdom of bacteria and the kingdom of archaea, or archaebacteria.

Eukaryotes includethree major kingdoms of multicellular organisms -- animal kingdoms , plants Andmushrooms , - as well as unicellular ones (for example, amoebas, ciliates, etc.), which are combined intokingdom protists , orprotozoa . The kingdom of protozoa, that is, single-celled eukaryotes, is currently recognized as a collective (that is, heterogeneous in origin) group and is divided into many kingdoms of organisms based on the structural features of intracellular structures and DNA sequences. Plants, animals, and fungi appear to have independently evolved from different groups of single-celled eukaryotes.

MODERN SYSTEMATICS. WILDLIFE DOMAINS

INCurrently, based on the structural features of cells and DNA sequences, scientists distinguish threedomain living nature (Fig. 2) are large groups that have diverged evolutionarily for a very long time and differ from each other in a whole set of characteristics. The structural features of their cells are different. Domains:

1. Archaea (formerly called archaebacteria).

2. Eubacteria (that is, true bacteria, as opposed to archaea). This group also includes cyanobacteria (formerly called blue-green algae) - photosynthetic prokaryotic organisms.

3. Eukaryotes - protozoa, plants, animals and fungi.

PROKARYOTES

Some prokaryotes are capable of photo- or chemosynthesis. For example, cyanobacteria, which were previously sometimes called blue-green algae, photosynthesize. Other prokaryotes feed by absorbing low molecular weight organic substances through the cell surface. Such bacteria can settle in food products, causing them to spoil or, conversely, contributing to the production of fermented milk products and the fermentation of vegetables (lactobacteria). Also, when settling in the human body, bacteria can cause diseases, for example, tetanus, cholera, diphtheria.

Archaea - a special, extremely peculiar group of prokaryotes that lives in extreme habitats - in hot springs, in the salty Dead Sea, etc., as well as in soil, animal intestines, sea water. Due to the presence of many unique characteristics, as well as genetic and molecular differences, archaea are currently classified as a separatedomain cellular organisms - a large independent group, along with true bacteria (eubacteria) and eukaryotes.

Plants

Plants are characterized by the presence of plastids - organelles, which include chloroplasts, due to which the vast majority of them are capable of photosynthesis. Plastids, apparently, were formed from cyanobacteria - symbionts of an ancient eukaryotic cell. Photosynthesis is the process of formation of organic substances from inorganic substances (carbon dioxide and water) using the energy of sunlight. Therefore, plants do not need organic substances for their life activity, that is, in generaldo not require organic nutrition . Such organisms are calledautotrophic , they form all the necessary organic substances themselves. They absorb water and minerals (salts) from the environment in the form of a solution. Photosynthetic plant cells, for example in leaves, secrete sugars and other organic substances that are transported to other tissues along vascular bundles, and cells in non-photosynthetic tissues (not green) absorb these substances by feeding on them. This type of nutrition is calledosmotrophic - absorption of low molecular weight organic substances from the environment by cells.

Plant cells are surrounded by a strongcell wall , which is based on polysaccharide fiberscellulose . A strong cell wall prevents the cell membrane from stretching under the influence of osmotic pressure (the pressure of water entering the cell). Plant cells are also characterized by the presencelarge central vacuole, which regulates the osmotic pressure and acidity of the environment in the cell, accumulates metabolic products unnecessary for the cell, which cannot be removed outside its boundaries, and in some cases serves for the deposition of reserve nutrients (Fig. 3).

Rice. 3. Plant cell structure

Animals

Animals areheterotrophs , i.e. feed on ready-made organic matter. Animal cells do not have a cell wall. Therefore, some types of animal cells are capable of contraction -muscle cells . This allows the animals to actively move (or push the medium through themselves, like stationary filter feeders). Multicellular animals have one or another typemusculoskeletal system , and to control movement and respond to external factors, it is formednervous system .

Animals move in search of sources of organic substances, that is, food. The animal ingests food and it enters the cavitydigestive system , where it is digested, whilepolymers (high molecular weight substances) of food are broken down intomonomers (their low molecular weight units). These monomers move from the digestive system through its lining into the blood (if any) and tissue fluid. This type of nutrition is calledholozoic . Basically, animal cells absorb low molecular weight substances dissolved in the blood and tissue fluid. Some animal cells are capable of engulfing large food particles (phagocytosis), such as the phagocytes of the immune system that ingest bacteria.

Rice. 4. Animal cell structure

Mushrooms

Third kingdom -mushrooms - in some ways it is similar to plants, and in others - with animals. Just like plants, fungi have a cell wall, but it is formed on the basis of a different polysaccharide -chitin . Without plastids, fungi are not capable of photosynthesis and feed on ready-made organic compounds, i.e. they areheterotrophs like animals. They also break down complex nutrient polymers usingenzymes , but, unlike animals, they do not have a digestive system and do not swallow food, but release enzymes into the environment. The resulting monomers are absorbed by the fungal cells in the form of a solution from the environment, that is, they exhibitosmotrophic food type. Unlike plants, fungi usually lack a large central vacuole. In most cases, fungal cells do not diverge after division, and since division occurs in the same plane, long threads are formed - hyphae. Hyphae can branch and, intertwining, form a network - mycelium, sometimes quite dense.

Rice. 5. Structure of a fungal cell

Unicellular eukaryotes

There are different single-celled eukaryotes with different cell features and types of nutrition. Among them there areheterotrophic unicellular , such as amoebas and ciliates. They feed by phagocytosis, that is, the absorption of solid food particles, such as bacteria, by cells, and pinocytosis, the absorption of droplets of nutrient fluid. These organisms are capable of movement: ciliates move due to the beating of the cilia covering the cell, and amoebas move through amoeboid movement (changing the shape of the cell and its flow, “crawling” along the surface to which they are attached).

There are alsoautotrophic unicellular , capable of photosynthesis, in particular unicellular algae - Chlamydomonas (moves, has flagella), Chlorella (immobile). Some single-celled organisms, such as green euglena, -mixotrophs , that is, they are able to switch between photosynthesis (autotrophy) and heterotrophic nutrition depending on environmental conditions.

Thus,The kingdoms of eukaryotes differ from each other in the structure of their cells and methods of nutrition .

Taxonomy of eukaryotes

The modern classification is based on new molecular data, as well as differences in the structure of cells of different groups of eukaryotes. The most important features for classification are the structure of flagella, chloroplasts and mitochondria.

The Unikonta group (uniflagellates) includes:

Amoebozoe

Tubular cristae of mitochondria

No plastids

Flagella are usually lost (present at some stages of development or non-functional), locomotion is usually due to pseudopodia.

Representatives: amoebas, myxomycetes, etc.

Opisthokonta (Postoflagellates)

No plastids

Flagellum one, posterior

Representatives: fungi (except for oomycetes and myxomycetes), choanoflagellates, animals (Metazoa), etc.

The Bikonta group (biflagellates) includes:

Archaeplastida

Lamellar cristae of mitochondria

Chloroplasts have double membranes, chlorophyll pigments, a and b

Representatives: red, green, charophyte algae, plants (from mosses to angiosperms), etc.

Excavates

Mitochondrial cristae shaped like tennis rackets

Chloroplasts with three membranes, chlorophyll pigments, a and b

Representatives: euglena algae, kinetoplastids (trypanosomes, leishmania), etc.

SAR (unites three clusters, mitochondrial cristae are tubular)

Rhizaria

Most lack plastids

There are rhizopodia

Representatives: foraminifera, sunfish, radiolarians, etc.

Alveolates

Apicoplast (remnant of a 4-membrane plastid) or 3(4)-membrane chloroplasts of dinoflagellate algae

There are alveoli under the cell membrane - membrane vesicles (empty, with protein or carbohydrate filler)

Representatives: dinoflagellate algae, ciliates, sporozoans, etc.

Stramenopiles

Plastids are 4-membrane, pigments are chlorophylls, a and c

Tripartite mastigonemes on flagella

Representatives: ochrophyte algae (including brown, golden, diatoms...), opalines, etc.

Features of the structure of an animal cell

Cytology - a science that studies the structure, development and functioning of cells.

Cell - the basic structural and functional unit of the body.

Organelles (organelles) - permanent parts of the cell that perform specific functions. Depending on their structure, organelles can be double-membrane, single-membrane or non-membrane.

Inclusions - temporary formations that make up the cell: starch grains, salt crystals, drops of fat, etc.

contains chromosomes (chromatin)

storage and transmission of hereditary information

cell (cytoplasmic) membrane

two layers of fats (lipids) and protein molecules

separates the internal contents of the cell;

selective transport of substances;

protective function;

receptor function

cytoplasm

internal environment of the cell;

consists of cytosol (hyaloplasm), organelles and inclusions

environment for all cellular processes: chemical reactions and transport of substances

Endoplasmic reticulum (reticulum) - ER

a network of membranes connecting the cell membrane to the nuclear membrane;

two kinds:

smooth EPS

rough ER (with ribosomes)

membrane synthesis;

smooth ER: synthesis and transport of fats and carbohydrates;

rough ER: protein synthesis and transport

Golgi apparatus (Golgi complex)

"stack" of single-membrane tubes, vesicles and cisterns near the nucleus

protein transport

enzyme synthesis

lysosome formation

lysosomes

small bubbles covered with a single-layer membrane;

maintains an acidic environment inside and contains digestive enzymes

intracellular digestion

vacuoles

single-membrane small bubbles

digestive vacuole: digestion;

contractile vacuole: release of excess water and undigested food debris from the cell

mitochondria

oval body surrounded by a two-layer membrane:

The outer membrane is smooth, the inner membrane forms folds (cristae)

energy metabolism (cellular respiration)

ribosomes

the smallest organelles (visible only with an electron microscope);

consist of two parts: large and small subunits

protein synthesis

cell center

two centrioles (cylinders of microtubules) located perpendicular to each other

cell division

COMPARISON OF THE STRUCTURE OF ANIMAL AND PLANT CELLS

The universal structural and functional unit of living things iscell . Cells are fairly small formations, usually visible only through a microscope, so the discovery and study of cells is closely related to the development of microscopic technology. Characteristic cell sizes: 1–5 μm for bacteria and 10–100 μm for animal and plant cells (micrometer, μm = 10−6 m, that is, a thousandth of a millimeter). The resolution limit of the human eye is about 100 microns (1/10 mm), but it must be taken into account that the object must be contrasty. Individual cells, even large ones, are often impossible to see within a tissue due to low contrast, and, as a rule, staining of the preparation is required to increase it. The case when a single cell with a size of the order of 100–200 microns can be seen with the naked eye is observation against a dark background in lateral light. Just as dust particles can be seen in an oblique beam of sunlight due to the scattering of light, in this case a cell can also be seen.

However, in most cases, optical instruments and preparation techniques are required to detect cells. Apparently, the first microscope was constructed by father and son Janssen at the end of the 16th century, but it was very imperfect.

The term “cell” was introduced by the English naturalist Robert Hooke (Fig. 1). He constructed a microscope and, using it to study various objects, in 1665 he discovered that a section of an ordinary wine cork was formed by regularly arranged rectangular cells (cells), which he called cells (Fig. 2 - illustration from his book “Micrography”) . He saw not living cells, but cell walls, since the cork is dead tissue. Subsequently, similar formations were discovered in other biological objects, and the term “cell” became generally accepted.

Rice. 1 Fig. 2

The Dutch scientist Antonie van Leeuwenhoek made a great contribution to the study of cells. At the end of the 17th century. He built a microscope and discovered various microorganisms in dental plaque, puddle water, and plant infusions. Leeuwenhoek's microscope was significantly improved by him and provided much more capabilities than the more primitive microscopes of his predecessors. Thus, the invisible world of microbes, which Leeuwenhoek called “animals,” was discovered. He also observed and sketched animal cells for the first time - sperm and erythrocytes (red blood cells). Leeuwenhoek described his observations in the book “Secrets of Nature Discovered by Anthony Leeuwenhoek Using Microscopes.”

After this, a period of rapid development of microscopy began, which led to the accumulation of information about the cellular structure of plant and animal tissues. As microscopic technology developed, it became clear that cells are universal components of living things.

Based on numerous observations of animal and plant cells in 1838, the botanist Matthias Schleiden and the histologist, physiologist, and cytologist Theodor Schwann formulatedcell theory . As further developmentcytology - cell science - this theory was developed and supplemented.

BASIC PROVISIONS OF CELL THEORY

The cell is the minimal structural and functional unit of living things. (“there is no life outside the cell”). Viruses do not have a cellular structure, but they exhibit all the properties of a living thing (such as metabolism, self-reproduction) only inside the living cell of the host they have infected.
All living organisms consist of cells and the extracellular substance formed by them. A multicellular organism is a system of cells and the intercellular substance secreted by them, formed as a result of the division of 1 original cell (fertilized egg - zygote).

Despite significant differences in the size and shape of cells, they all havegeneral plan of the building . Schwann and Schleiden believed that all cells have a membrane, cytoplasm and a nucleus, which is typical for plant and animal cells, but further development of microscopy made it possible to find out that there are also cells without a nucleus (that is, without a nuclear membrane), for example, bacterial cells. They are much smaller than plant and animal cells. However, the chemical foundations and general principles of the structure and functioning of cells are common to all living organisms. This is one of the proofs of the unity of origin of living nature and the kinship of all life on Earth.

Cells do not arise anew from non-cellular matter, but are formed by division of pre-existing cells (the so-called Virchow addition, made by Rudolf Virchow in 1858). It is assumed that billions of years ago cells arose abiogenically in the process of the origin of life from non-living matter, but it is believed that this is currently impossible because suitable conditions are not available. Even the great French scientist Louis Pasteur (1822–1895), in his experiments with boiling nutrient media in special flasks with curved spouts, where microorganisms and their spores did not fall, proved the impossibility of the spontaneous generation of life from inanimate matter.

pro- and eukaryotes

All cellular organisms are divided into two groups:

prokaryotes , orpre-nuclear , without a nuclear membrane;

eukaryotes , ornuclear , in which the genetic material (DNA) is located in the nucleus and is separated from the cytoplasmnuclear membrane.

Prokaryotes are very small, single-celled organisms without a nucleus. Among them we can highlightkingdom bacteria and kingdom archaea (formerly archaebacteria).

Eukaryotes include three main kingdoms of multicellular organisms -kingdoms of animals, plants and fungi, - as well as unicellular eukaryotes (for example, amoebas, ciliates, etc.), which are combined intokingdom protists, orprotozoa (currently recognized as a collective, that is, a group of heterogeneous origin and divided into many kingdoms of unicellular organisms).

FEATURES OF PRO- AND EUKARYOTIC CELLS

Pro- and eukaryotic cells are very different. Prokaryotes are more ancient and simply structured organisms (Fig. 3). Their cells are very small, on the order of several micrometers (1–5 µm). They do not have a nucleus and practically no internal membrane structures - organelles characteristic of eukaryotic cells. They usually have a cell wall on top of the membrane and sometimes an additional mucous capsule. DNA is found in the cytoplasm, this structure is callednucleoid (“nucleus” - core, “oides” - similar). DNA in prokaryotes is circular. In addition to the main chromosome, there may be additional small rings of DNA -plasmids . There is a lot in the cytoplasmribosomes - organelles like granules that carry out protein biosynthesis. Prokaryotic cells may have flagella.

Some prokaryotes are capable of photo- or chemosynthesis. For example, they photosynthesizecyanobacteria , which used to be sometimes called blue-green algae. Other prokaryotes feed by absorbing low molecular weight organic substances through the cell surface. Such bacteria can settle in food products, causing them to spoil or, conversely, contributing to the production of fermented milk products and the fermentation of vegetables (lactobacteria). Also, when settling in the human body, bacteria can cause diseases, such as tetanus, cholera, and diphtheria.

Archaea - a special, extremely peculiar group of prokaryotes that lives in extreme habitats - in hot springs, in the salty Dead Sea, etc., as well as in soil, in the intestines of animals.

Rice. 3. Structure of a prokaryotic cell

Eukaryotic cells are many times larger (10–100 µm) and much more complex in structure (Fig. 4) than prokaryotic cells. In the cytoplasm they have many complex structuresorganelles , including membrane ones, for example, the endoplasmic reticulum (ER), OR (its other name) the endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, mitochondria, and sometimes plastids.

The nucleus of eukaryotes hasdouble membrane nuclear envelope . Inside the nucleus there are DNA molecules; they are not circular, but linear, and there are usually several or many of them (at least two). They are complexed with proteins in chromosomes. The structure of a large and complex eukaryotic cell is supported by a system of protein fibers -cytoskeleton , which is practically not developed in prokaryotes. Cytoskeletal threads are also involved in the distribution of chromosomes to daughter cells during eukaryotic division.

Eukaryotic cells, as a rule, are able to absorb particles from the environment by invaginating the membrane, which is not typical for prokaryotes. This process is calledendocytosis . The reverse process is also characteristic of eukaryotes -exocytosis - secretion of substances by the cell by fusion of vesicles with the outer membrane. The cytoskeleton and a large number of membrane organelles, apparently, allowed eukaryotic cells to acquire large sizes during evolution. Found only in eukaryotestrue multicellularity .

Detailed information about the organelles of eukaryotic cells can be found in separate topics dedicated to them.

Rice. 4. Structure of a eukaryotic cell

The main (though not all) differences between pro- and eukaryotic cells are shown in the table.

lysosomes, vacuoles

No

There is

mitochondria, plastids

No

There is

ribosomes

smaller

more

DNA

1 ring

many linear chromosomes

cytoskeleton

not developed

developed

nitrogen fixation

It happens

can not be

endocytosis

No

There is

flagella

external
(not covered with membrane)

internal
(covered with membrane)

The structure of prokaryotic cells. Bacteria

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Cellsprokaryote do not have a nuclear membrane (Greek “pro” - before, “karyon” - core), they are small in size (usually 1 - 5 microns) and simple in structure.

SURFACE APPARATUS

All cells, including prokaryotic cells, are surrounded bycytoplasmic membrane . It isolates the contents of the cell from the environment, transports substances from and into the cell, and receives signals from the environment. Thus, the membrane ensures the maintenance of a constant intracellular environment.

Based on the structure of the surface apparatus, bacteria are divided into two large groups -gram-positive (gram+) andgram-negative (gram–). These names are given because of the varying ability of these cells to be Gram stained (a specific staining method).

In gram-positive bacteria, the murein layer is quite thick. Their cell walls also contain special compounds -teichoic acids .

In gram-negative bacteria, a thin murein layer is covered on top by a second membrane. Between the membranes there isperiplasmic space .

Rice. 1. Surface structure of gram+ and gram– bacteria

Some types of bacteria have an additional outer layer on top of the cell wall calledcapsule . Unlike the wall, it is loose and transparent. It consists of loosely bound polysaccharides and protects the cell from mechanical damage, and in the case of pathogenic bacteria, from the defense systems of the host body.

Rice. 2. Bacterial capsule. Colorized electron micrograph

Rice. 3. Structure of a bacterial cell

INTERNAL STRUCTURE

In an electron micrograph of the inside of a bacterial cell, an electron microscope shows areas of varying density.

Rice. 4

The part that is more transparent to electrons (light) contains DNA and is callednucleoid (Greek “nucleus” - core, “oides” - similar). It is not separated from the rest of the cell, called the cytoplasm, and has approximately the same composition. DNA in prokaryotes is usually represented by one circular molecule, attached to the cytoplasmic membrane at a certain point.

Ribosomes are scattered throughout the internal space of a bacterial cell, the number of which can reach 10,000 per cell. Because of this, the cytoplasm appears darker and more granular in electron micrographs. In addition, inside the cell there are a few invaginations of the cytoplasmic membrane, calledmesosomes . Previously it was believed that they are the site of ATP synthesis; According to new data, these are most likely fixation artifacts, and respiration occurs in other areas of the membrane.

Sometimes granules of some substances are observed in the cells of some bacteria. They may contain reserve nutrients (polysaccharides, fat drops, polyphosphates) or metabolic waste that cells cannot excrete (sulfur, iron oxides, etc.). Such granules are calledinclusions (see Fig. 5).

Rice. 5

Outside the bacterial cell membrane, long filamentous structures of two types can be located. The first of them areflagella - are protein helices capable of rotating relative to the bacterial cell membrane and ensuring the movement of bacteria by “screwing” the bacteria into the medium. Not all bacteria have flagella. The second group of threads -drank - not capable of movement, but ensures the attachment of bacteria to other cells.

SPORE FORMATION

Some bacteria are capable of formingdisputes . Spores in bacteria do not serve to reproduce, but to endure unfavorable conditions. The spore is formed inside the cell (one in each cell). It necessarily contains the genetic material of the bacterium. The spore covers itself with a dense shell, after which all remaining external parts of the cell die.

Rice. 7. Spores in the cells of the anthrax pathogen

Bacterial spores generally survive boiling. They can only be destroyed by autoclaving (pressure steam treatment, usually at a temperature of 120 OC), calcination. The destruction of all bacteria and their spores is calledsterilization .

ECOLOGY OF BACTERIA

Bacteria are able to exist in a wide variety of conditions. They are found in the atmosphere at an altitude of several kilometers and on the bottom of the oceans. Some types of bacteria live even several kilometers underground in oil and coal formations.

Bacteria, despite their small size, carry out large-scale processes in the biosphere.

1. Bacteria are one of the most important groupsdecomposers - organisms that decompose dead organic matter.

2. Many bacteria are capable of producing organic substances from inorganic ones, that is, they areautotrophs . They can do this at the expensephotosynthesis using light energy (photoautotrophs, primarilycyanobacteria - green, contain chlorophyll, are the ancestors of chloroplasts) orchemosynthesis - oxidation of inorganic substances (chemoautotrophs).

Rice. 8. Cyanobacteria (photosynthetics)

Thus, prokaryotes can be producers of biomass -producers , in some biocenoses the most important or the only ones. Thus, chemosynthetic bacteria, primarily those that oxidize hydrogen sulfide, are the only producers in deep-sea ecosystemsblack and white smokers - oceanic geothermal sources.

Rice. 9

3. Only bacteria are capable of converting molecular nitrogen from the atmosphere into nitrogen from organic compounds, i.e., carrying outnitrogen fixation . Nitrogen is fixed, for example, by nodule bacteria - symbionts of leguminous plants, as well as cyanobacteria.

BACTERIA AND HUMANS

Bacteria play an important role in human life.

First of all, we must say aboutpathogenic bacteria , causing various diseases of humans, domestic animals and cultivated plants (see the topic “Bacterial and viral diseases of humans”).

In addition, bacteria cause food spoilage and destruction of various materials.

A number of bacteria are used by humans in their economic activities. Bacteria are used in the food industry to produce yoghurts, curdled milk, cheeses and a number of other lactic acid products. Thanks to bacteria, the processes of pickling cabbage, pickling cucumbers, and ensiling feed are carried out.

Fermentation processes carried out by bacteria are an industrial source of a number of substances, such as acetone, lactic and butyric acid.

Some bacteria and related actinomycetes produceantibiotics , used in medicine. Bacteria are a source for obtaining a numberenzymes , used in the food industry, medicine and other industries.

ARCHAEA

Nuclear-free, that is, prokaryotic cells, are also found in a completely special group of living organisms, different from bacteria and eukaryotes -archaea (See the topic “The main kingdoms of living organisms”). In size and structure, archaeal cells are very similar to bacterial cells, but they differ greatly in biochemical and molecular biological characteristics. For example, some archaea have a membrane that is completely different from the membranes of all other organisms - it does not consist of phospholipids, but of ethers of polyisoprenoid alcohols (that is, alcohols formed by isoprene units, such as natural rubber). The archaeal cell wall consists of eitherpseudomureina , resembling murein, or from proteins, which is also not found in other organisms. Archaea, unlike other bacteria, never form spores.

Rice. 10. Cells of methanogenic archaea (colorized electron micrograph)

Rice. 11. Redwood City, California. Aerial view. Purple archaea live in salty ponds

Viruses are non-cellular life forms

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Virus (from Lat. virus - poison) - the simplest form of life, a microscopic particle, which is a nucleic acid molecule (DNA or RNA) enclosed in a protein shell (capsid ) and capable of infecting living organisms.

Viruses, with rare exceptions, contain only one type of nucleic acid: either DNA or RNA (some, such as mimiviruses, have both types of molecules).

Currently, viruses are known that reproduce in the cells of plants, animals, fungi and bacteria (the latter are usually calledbacteriophages ). Viruses that infect other viruses have also been discovered (satellite viruses ).

Rice. 1 Bacteriophage

Structure of viruses

Simply organized viruses consist of a nucleic acid and several proteins that form a shell around it -capsid. Examples of such viruses are the tobacco mosaic virus. Its capsid contains one type of protein with a small molecular weight.

Rice. 2 Tobacco mosaic virus

Complexly organized viruses have an additional shell - protein or lipoprotein; sometimes the outer shells of complex viruses contain carbohydrates in addition to proteins. Examples of complexly organized viruses are the pathogens of influenza and herpes. Their outer shell is a fragment of the nuclear or cytoplasmic membrane of the host cell, from which the virus exits into the extracellular environment.

Rice. 3 Influenza virus

Spread of viruses on Earth

Viruses are one of the most common forms of existence of organic matter on the planet in terms of numbers: the waters of the world's oceans contain a colossal number of bacteriophages (about 250 million particles per milliliter of water), their total number in the ocean is about 4 × 1030, and the number of viruses (bacteriophages) in bottom sediments of the ocean practically does not depend on depth and is very high everywhere. The ocean is home to hundreds of thousands of species (strains ) viruses, the vast majority of which have not been described, much less studied. Viruses play an important role in regulating the population size of some species of living organisms (for example, the feralization virus reduces the number of arctic foxes several times every few years).

Viral infection process

Conventionally, the process of viral infection on the scale of one cell can be divided into several overlapping stages:
cell penetration
cell reprogramming
persistence (transition to an inactive state)
creation of new viral components
maturation of new viral particles and their exit from the cell

PENETRATION INTO THE CELL

At this stage, the virus needs to deliver its genetic information inside the cell. Some viruses also carry their own proteins necessary for its implementation. Different viruses use different strategies to penetrate the cell: for example, picornaviruses inject their RNA through the plasma membrane, and orthomyxovirus virions are captured by the cell during endocytosis, enter the acidic environment of lysosomes, where their final maturation occurs (deproteinization of the viral particle), after which the RNA is in complexed with viral proteins overcomes the lysosomal membrane and enters the cytoplasm. Viruses also differ in the localization of their replication; some viruses (for example, the same picornaviruses) multiply in the cytoplasm of the cell, and some (for example, orthomyxoviruses) - in its nucleus.

CELL REPROGRAMMING

When a cell is infected with a virus, special antiviral defense mechanisms are activated. Infected cells begin to synthesize signaling molecules - interferons, which transfer surrounding healthy cells into an antiviral state and activate the immune system. Damage caused by the virus multiplying in a cell can be detected by internal cell control systems, and the cell will have to "commit suicide" in a process called apoptosis or programmed cell death. Its survival directly depends on the ability of the virus to overcome antiviral defense systems. It is not surprising that many viruses (for example, picornaviruses, flaviviruses) during evolution acquired the ability to suppress the synthesis of interferons, the apoptotic program, etc.

In addition to suppressing antiviral defenses, viruses strive to create the most favorable conditions in the cell for the development of their offspring.

PERSISTENCE

Some viruses can becomelatent state (the so-called persistence for eukaryotic viruses or lysogeny for bacteriophages - bacterial viruses), weakly interfering with the processes occurring in the cell, and are activated only under certain conditions. This is how, for example, the reproduction strategy of some bacteriophages is constructed - as long as the infected cell is in a favorable environment, the phage does not kill it, is inherited by daughter cells and is often integrated into the cellular genome. However, when a bacterium infected with a lysogenic phage enters an unfavorable environment, the pathogen seizes control of cellular processes, so that the cell begins to produce materials from which new phages are built (the so-called lytic stage). The cell turns into a factory capable of producing many thousands of phages. Mature particles leaving the cell rupture the cell membrane, thereby killing the cell. Some cancers are associated with the persistence of viruses (for example, papovaviruses).

CREATION OF NEW VIRUS COMPONENTS

In the most general case, virus replication involves three processes:

Transcription of the viral genome, that is, synthesis of viral mRNA.

Its translation, that is, the synthesis of viral proteins.

Many viruses have control systems that ensure optimal consumption of host cell biomaterials. For example, when enough viral mRNA has accumulated, transcription of the viral genome is suppressed, and replication, on the contrary, is activated.

MATURATION OF VIRIONS AND EXIT FROM THE CELL

Eventually, the newly synthesized genomic RNA or DNA is dressed with appropriate proteins and leaves the cell. It should be said that an actively replicating virus does not always kill the host cell. In some cases (for example, orthomyxoviruses), daughter viruses bud from the plasma membrane without causing its rupture. Thus, the cell can continue to live and produce the virus.