What cell organelles perform a hereditary function. Cell structure. The starting materials for photosynthesis are

1) The main organelles of a plant cell classification and functions.

Organoid name	Structure			Functions
Membrane	Consists of fiber. She is very resilient (this is her physical property). Consists of 3 layers: internal and external of which consist of protein molecules; middle - from a two-layer molecule of phospholipids (hydrophilic outside, hydrophobic inside). The outer shell is soft.			Support function Passive and active exchange in-in; protective; transport in-in from cell to cell
plasmalemma	Very thin. The outer side is formed from carbohydrates, the inner side is from a thick protein molecule. The chemical basis of the membrane is: proteins - 60%, fats - 40% and carbohydrates - 2-10%.			*Permeability; *Transport function; * Protective f-I.
Cytoplasm	A semi-liquid substance that surrounds the cell nucleus. The base is hyoplasm. It contains granular bodies, proteins, enzymes, nucleic acids, carbohydrates, ATP molecules.			It can change from one state (liquid) to another - solid and vice versa.
MEMBRANE ORGANOSES
ER (endoplasmic reticulum)	Consists of cavities and diggers. It is divided into 2 types - granular and smooth. Granular - oblong hoofs and cavities; there are dense granules (ribosomes).			* Takes into account in the synthesis of glycolipid molecules and their transportation; * Takes into account in protein biosynthesis, transportation of synthesizing substances.
Golgi complex	It occurs in the form of a network interconnected by a system of cavities. They look like tanks .. It can be oval or heart-shaped.			* Takes into account in the formation of cell waste products; * Breaks down to dictyosome (during division); *Excretory function.
Lysosome	Means a solvent of things. The composition contains enzymes of hydrolysis. The lysosome is surrounded by a lipoprotein membrane; when it is destroyed, lysosome enzymes act on the external environment.			*F-I suction; *selection function; *Protective function.
Mitochondria	In the cell, it has the form of grains, granules and is found in quantities from 1 to 100 thousand. It belongs to two-membrane organoids and comp. from: a) outer membrane, b) inner membrane, c) intermembrane space. In the matrix of mitochondria there are circular DNA and RNA, ribosomes, granules, bodies. Proteins and fats are synthesized. Mitria consists of 65-70% protein, 25-30% lipids, nucleic acids and vitamins. Mitochondria is a protein synthesis system.			* F-yu mit-rii is sometimes performed by chloroplasts; * Transport facility; *Protein synthesis; * ATP synthesis.
Plastids are membranous organelles	It is the main organelle that grows. cells. 1) chloroplasts are green, oval in shape, inside there are many membrane thylakoids and stroma proteins that make up its mass. There are nucleic acids - DNA, RNA, ribosomes. They reproduce by division. 2) chromoplasts - different color. They contain various pigments. 3) leukoplasts - colorless. They are found in the tissues of germ cells, cytoplasms of spores and maternal gametes, seeds, fruits, roots. They are the synthesis and accumulation of starch.			* Carry out the process of photosynthesis * Attract the attention of insects *Store nutrients
NON-MEMBRANE ORGANOS
Ribosome		Comp. of two subunits: large and small. It has an ovoid shape. The synthesized polypeptide chain passes between the subunits.	*Protein biosynthesis occurs here; *Synthesis of a protein molecule; * Transport function.
Cell Center		Comp. from 2 centrioles. The center divides in half before cell division and pulls up from the equator to the poles. Cl. the center is doubled by division.	*Accounts for meiosis and mitosis
cell nucleus		Has a complex structure. Nuclear shell comp. from 2 three-layer membranes. During the period of the cell, the nuclear membrane disappears and is re-formed in new cells. Membranes St. nna semi-permeability. Core comp. from chromosomes, nuclear juice, nucleolus, RNA, and other parts that preserve hereditary information and properties of a living organism.	* Protective function

2) Leaf classification:

• simple - one leaf blade;
• complex - several leaf blades that have their own petiole, sitting on a common axis - rachis.

Compound leaves: A - unpaired pinnate; B - paired pinnate; B - ternary; G - palmately complex; D - doubly paroperistoslozhny; E - twice unpaired pinnate;

Types of dismemberment of the plate:

Classification simple leaves. Generalized scheme of leaf shapes:

The main types of tops, bases and edges of leaf blades: A - tops: 1 - sharp; 2 - pointed; 3 - dull; 4 - rounded; 5 - truncated; 6 - notched; 7 - pointed; B - bases: 1 - narrow wedge-shaped; 2 - wedge-shaped; 3 - wide wedge; 4 - descending; 5 - truncated; 6 - rounded; 7 - notched; 8 - heart-shaped; B - edge of the sheet: 1 - serrate; 2 - doubly serrate; 3 - gear; 4 - crenate; 5 - notched; 6 - solid.

The main types of venation of the leaves of angiosperms: 1 - pinnate; 2 - pinnatiform; 3 - pinnate; 4 - palmate; 5 - finger-loop-shaped; 6 - parallel; 7 - digitiform; 8 - arcuate.

Methods for attaching leaves to a stem:
Long-petiolate, sessile, vaginal, pierced, short-petiolate, descending.

3) Rosaceae. Forms: trees, shrubs, herbs. Ks - pivotal, many herbaceous have a rhizome. The stem is erect, some are shortened with a mustache, others have spines. Leaf: simple and complex with stipules

Formula: correct, bisexual

Bisexual Ca 5 Co 5 A ∞ G 1-∞ (perianth above ovary).

Inflorescence corymb, raceme, solitary, umbel

Fruit drupe, nut, berry

Subfamilies: spirea (spiraea, fieldfare, volzhanka), rose hips (rose hips, raspberries, blackberries, cotton, strawberries, strawberries), apple (apple, pear, mountain ash, quince, hawthorn), plum (cherry, plum, apricot, peach, bird cherry) , almond)

Meaning: food, lek (pluck), dec (rose, spirea)

cell organelles and their presence depends on the cell type. Modern biology divides all cells (or alive organisms) into two types: prokaryotes And eukaryotes. Prokaryotes are non-nuclear cells or organisms, which include viruses, prokaryotic bacteria and blue-green algae, in which the cell consists directly of the cytoplasm, in which one chromosome is located - DNA molecule(sometimes RNA).

eukaryotic cells have a nucleus containing nucleoproteins (histone protein + DNA complex), as well as other organelles. Eukaryotes include most modern known to science unicellular and multicellular living organisms (including plants).

Organoid name

The structure of the organoid

Organoid functions

Cytoplasm	The internal environment of the cell, which contains the nucleus and other organelles. It has a semi-liquid, fine-grained structure.	Performs a transport function. Regulates the rate of flow of metabolic biochemical processes. Provides interaction between organelles.
Ribosomes	Small spherical or ellipsoidal organelles with a diameter of 15 to 30 nanometers.	They provide the process of synthesis of protein molecules, their assembly from amino acids.
Mitochondria	Organelles that have a wide variety of shapes - from spherical to filamentous. Inside the mitochondria there are folds from 0.2 to 0.7 microns. The outer shell of mitochondria has a two-membrane structure. The outer membrane is smooth, and on the inner there are outgrowths of the cruciform different shapes with respiratory enzymes.	Enzymes on membranes ensure the synthesis of ATP (adenosine triphosphoric acid). Energy function. Mitochondria supply energy to the cell by releasing it during the breakdown of ATP.
Endoplasmic reticulum (ER)	The membrane system in the cytoplasm that forms channels and cavities. There are two types: granular, on which there are ribosomes and smooth.	Provides processes for the synthesis of nutrients (proteins, fats, carbohydrates). Proteins are synthesized on granular ER, while fats and carbohydrates are synthesized on smooth ER. Provides circulation and delivery of nutrients within the cell.
plastids(organelles peculiar only to plant cells) are of three types:	Double membrane organelles
Leucoplasts	Colorless plastids found in tubers, roots and bulbs of plants.	They are an additional reservoir for storing nutrients.
Chloroplasts	Organelles are oval in shape and green in color. They are separated from the cytoplasm by two three-layer membranes. Inside the chloroplasts is chlorophyll.	Transform organic matter from inorganic matter using the energy of the sun.
Chromoplasts	Organelles, from yellow to brown, in which carotene accumulates.	They contribute to the appearance of parts with yellow, orange and red color in plants.
Lysosomes	Rounded organelles with a diameter of about 1 micron, having a membrane on the surface, and inside - a complex of enzymes.	digestive function. Digest nutrient particles and eliminate dead parts of the cell.
Golgi complex	It may be of different shapes. Consists of cavities separated by membranes. Tubular formations with bubbles at the ends depart from the cavities.	Forms lysosomes. Collects and removes organic substances synthesized in EPS.
Cell Center	It consists of a centrosphere (a compacted area of ​​the cytoplasm) and centrioles - two small bodies.	Performs an important function for cell division.
Cell inclusions	Carbohydrates, fats and proteins, which are non-permanent components of the cell.	Spare nutrients that are used for the life of the cell.
Organelles of movement	Flagella and cilia (outgrowths and cells), myofibrils (filamentous formations) and pseudopodia (or pseudopodia).	They perform a motor function, and also provide the process of muscle contraction.

cell nucleus is the main and most complex organelle of the cell, so we will consider it separately.

Option 1.

I. Solve the tests.

1. What cell organelle is found only in a plant cell?

A) Nucleus B) Vacuole C) Digestive vacuole D) Contractile vacuole

1. What organisms form mycelium?

A) Fungi B) Trees C) Bacteria D) Algae

1. What is the name of the body of a multicellular algae?

A) Mycorrhiza B) Rhizoids C) Thallus D) Rhizome

1. What moss makes peat?

A) Kukushkin flax B) Riccia C) Marchantia D) Sphagnum

1. Select the reproductive organ of the plant.

A) Rhizome B) Flower C) Stem D) Leaf

1. Which plant belongs to the cruciferous family?

A) Common peas B) Wild cabbage C) Cinnamon rosehip D) Potatoes

1. What animals have a body covered with bony scales?

A) Fish B) Toad C) Crocodile D) Birds

1. What animals have ray symmetry?

A) Rhizomes B) Chordates C) Coelenterates D) Insects

1. What animals are called social?

A) Primates B) Fish C) Insects D) Spiders

1. Which animals develop with metamorphosis?

A) Crocodile B) Butterfly C) Birds D) Locust

1. What worms are dioecious?

A) Round B) Ringed C) Flat

1. What class of arthropod type has three body parts?

A) Arachnids B) Crustaceans C) Insects

1. Answer the questions.

13. A large ciliate balantidia lives in the human intestine. Unlike the shoe, it lacks a cellular mouth, pharynx, and digestive vacuole.

Explain why?

14. How do the tree and the mycelium of the fungus, which form mycorrhiza, depend on each other?
Test for students in biology for grades 6-7.

Option 2.

1. Solve tests.

1. What cell organelle does only a plant cell have?

A) Chloroplast B) Nucleus C) Digestive vacuole D) Contractile vacuole

What organism forms the thallus?

A) Mosses B) Lichens C) Trees D) Mushrooms

3. How do algae attach to the substrate?

A) Rhizome B) Mycelium C) Rhizoid D) Bulb

4. What kind of moss is considered green?

A) Sphagnum B) Riccia C) Marchantia D) Kukushkin flax

5. Where does the gametophyte stage begin in a fern?

A) On the fronds B) On the rhizome C) On the sporangia D) On the outgrowth

6. Which plant belongs to the nightshade family?

A) Fragrant tobacco B) Common rose C) Wild cabbage D) Sunflower

7. In which animals is the body covered with horny scales?

A) Fish B) Birds C) Mammals D) Reptiles

8. In which animal outgrowths of the cytoplasm are formed?

A) Hydra B) Amoeba C) Ciliates D) Euglena

9. What animal can reproduce by budding?

A) Earthworm B) Insect C) Hydra D) Grape snail

10. Which of the mammals lays eggs?

A) Kangaroo B) Penguins C) Platypus D) Monkey

What first class of animals developed limb girdles and limbs?

A) Amphibians B) Birds C) Fish D) Reptiles

1. What animal develops without metamorphosis?

A) Frog B) Butterfly C) Monkey D) Triton
II. Answer the questions.

1. Explain why the ciliate shoe is considered the most complex unicellular animal in structure?

14. Why angiosperms considered the most common on earth.

Prokaryotes and eukaryotes

The first organisms that appeared 3.0 - 3.5 billion years ago, lived in anoxic conditions, were anaerobic heterotrophs.

They used organic matter of abiogenic origin as nutrients and obtained energy from oxygen-free oxidation and fermentation.

A remarkable event was the emergence of the process of photosynthesis, when the energy of sunlight began to be used for the synthesis of organic substances.

Bacterial photosynthesis at the first stages was not accompanied by the release of oxygen (the first photoautotrophs, use carbon dioxide as a source of carbon and H2S as a source of hydrogen).

6CO2 + 12H2S + Q light = C6H12O6 + 6S2 + 6H2O

Later, at blue-green, a photosystem appears that can split water and use its molecules as hydrogen donors.

Photolysis of water begins, during which oxygen is released. Photosynthesis of blue-greens is accompanied by the accumulation of oxygen in the atmosphere and the formation of an ozone screen.

Oxygen in the atmosphere stopped the process of abiogenic synthesis of organic compounds, but led to the emergence of an energetically more favorable process - respiration. Appear aerobic bacteria in which the products of glycolysis undergo further oxidation with the help of oxygen to carbon dioxide and water.

The symbiosis of a large anaerobic cell (probably belonging to archaebacteria and retaining the enzymes of glycolytic oxidation) with aerobic bacteria turned out to be mutually beneficial, and aerobic bacteria eventually lost their independence and turned into mitochondria.

The loss of independence is associated with the loss of part of the genes that have passed into the chromosomal apparatus of the host cell.

But still, mitochondria retained their own protein-synthesizing apparatus and the ability to reproduce.

An important stage in the evolution of the cell was the emergence of eukaryotes, in which the isolation of the nucleus occurred, the separation of the genetic apparatus of the cell from metabolic reactions.

Various methods of heterotrophic nutrition led to the formation of the kingdom of Fungi and the kingdom of Animals. In fungi, chitin is present in the cell wall, reserve nutrients are deposited in the form of glycogen, and urea is the product of protein metabolism.

Symbiosis with cyanobacteria led to the appearance of chloroplasts.

Chloroplasts have also lost some of their genes and are semi-autonomous organelles capable of self-reproduction. Their appearance led to the development along the path with an autotrophic type of metabolism and the separation of some organisms into the plant kingdom. For plants, the characteristic substance of the cell wall is fiber, the reserve substance is deposited in the form of starch, the presence of large vacuoles is characteristic and higher plants there are no centrioles in the cell center.

Many facts speak in favor of the symbiotic origin of mitochondria and chloroplasts.

Firstly, their genetic material is represented by a single circular DNA molecule (as in prokaryotes), and secondly, their ribosomes are similar in mass, in the structure of rRNA and ribosomal proteins to those of aerobic bacteria and blue-green bacteria. Thirdly, they reproduce as prokaryotes and, finally, the mechanisms of protein synthesis in mitochondria and bacteria are sensitive to some antibiotics (streptomycin), and cycloheximide blocks protein synthesis in the cytoplasm.

In addition, one species of amoeba is known that do not have mitochondria and live in symbiosis with aerobic bacteria, and cyanobacteria (blue-green), similar in structure to chloroplasts, were found in the cells of some plants.

Further evolution led to the separation and preservation of two empires - Precellular and Cellular. Pre-cellular are united in the kingdom Viruses, Cellular - in two super-kingdoms Prokaryotes (pre-nuclear) and Eukaryotes (nuclear).

Prokaryotes are included in the kingdom of Drobyanok and are divided into three sub-kingdoms: the most ancient belong to the sub-kingdom of Archaebacteria, another group of bacteria belongs to the sub-kingdom of Eubacteria, and prokaryotes that are capable of releasing oxygen during photosynthesis unite in the Blue-Green sub-kingdom.

Anchoring. Conversation. The work of students with a notebook and a codegram.

Homework assignment. Read the paragraph and answer the questions.

Annex 1.

Appendix 2

			Write down the numbers of questions, against them - the correct answers: 1. What organelles have one membrane outside? 2. What organelles have two membranes outside? 3. What non-membrane organelles do you know? 4. What organelle is called the "export system of the cell"? Here there is an accumulation, modification and removal of substances from the cell. This is where lysosomes are formed. 5. What organelles provide the biosynthesis of proteins in the cytoplasm of the cell? 6. What organelles are responsible for providing the cell with energy, called "respiratory organelles"? 7. What organelles are responsible for the breakdown of complex organic molecules into monomers, even food particles that enter the cell by phagocytosis? 8. What organelles are absent in the cells of higher plants? 9. What organelle is responsible for the formation of the cytoskeleton? Write down the answers and sit down.

Appendix 3

Task 7. "Organoids of the cell".

**Test 1. Single-membrane cell organelles:

1. Ribosomes. 6. Lysosomes.

2. Golgi complex. 7. EPS.

3. Mitochondria.

8. Myofibrils from actin and myosin.

**Test 2. Double-membrane cell organelles:

1. Ribosomes. 6. Lysosomes.

2. Golgi complex. 7. EPS.

Chloroplasts. 9. Cilia and flagella of eukaryotes.

5. Cytoskeleton. 10. Cell center.

**Test 3. Non-membrane cell organelles:

1. Ribosomes. 6. Lysosomes.

2. Golgi complex. 7. EPS.

3. Mitochondria. 8. Myofibrils from actin and myosin.

4. Chloroplasts. 9. Cilia and flagella of eukaryotes.

5. Cytoskeleton. 10. Cell center.

Test 4 An organelle that forms lysosomes and is called the "export system of the cell":

2. Golgi complex.

3. Cell center.

4. Mitochondria.

Test 5 Organelles that provide the biosynthesis of proteins in the cytoplasm of the cell:

1. Mitochondria.

2. Chloroplasts.

3. Golgi complex.

4. Ribosomes.

Test 6 The organelles responsible for providing the cell with energy, called "respiratory organelles":

1. Mitochondria.

2. Chloroplasts.

3. Golgi complex.

4. Ribosomes.

Test 7 Organelles responsible for the breakdown of complex organic molecules into monomers, even food particles that enter the cell by phagocytosis:

Lysosomes.

2. Ribosomes.

4. Golgi complex.

Test 8 Organelles absent in higher plant cells:

1. Mitochondria.

2. Chloroplasts.

3. Golgi complex.

4. Centrioles.

Test 9 The organelle responsible for the formation of the cytoskeleton:

1. Golgi complex.

2. Cell center.

4. Nucleolus.

Test 10 Organelles capable of converting energy sunlight into the energy of chemical bonds of the formed organic matter:

Mitochondria.

2. Chloroplasts.

3. Lysosomes.

4. Golgi complex.

Lesson 5

Tasks. Continue studying the diversity of life forms on Earth. Consider the features of the structure, vital activity of viruses and their significance in nature and for humans using the example of HIV.

Continue the formation of evolutionary ideas about the development of the organic world and the emergence of non-cellular life forms. Repeat the material and check the knowledge of students on the topic "Cell nucleus. Prokaryotes and eukaryotes." Report on the test at the next lesson.

Equipment.Demo material: tables by general biology, codogram, fragments of the film "Immunity", slides "Cage".

During the classes:

Repetition.

Written work with cards for 10 min.

How is the structure of the kernel related to the functions it performs?

2. What is the difference between prokaryotes and eukaryotes?

3. What are the similarities between prokaryotes and eukaryotes?

Working with a card at the blackboard: Appendix 2.

Computer testing: appendix 3.

oral repetition.

Learning new material. Explanation with the help of tables, fragments of the film, filmstrip, codogram.

1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 |

The structure of the cytoplasm

The cytoplasm is the internal contents of the cell and consists of the main substance (hyaloplasm) and the various elements inside it. cell structures(organelles and inclusions).

Hyaloplasm (matrix)- an aqueous solution of inorganic and organic substances that can change its viscosity and is in constant motion.

Cytoplasmic structures cells are represented by organelles and inclusions.

Organelles (organelles)- permanent and required components most cells that have a certain structure and perform vital functions. Inclusions- unstable structures of the cytoplasm in the form of granules (starch, glycogen, proteins) and drops (fats).

Organelles are membranous (single-membrane and double-membrane) and non-membrane.

Single membrane cell organelles

These include the endoplasmic reticulum, the Golgi apparatus, lysosomes, vacuoles, which form a single cell membrane system.

Endoplasmic reticulum (endoplasmic reticulum)- a system of interconnected cavities, tubules and channels, delimited from the cytoplasm by one layer of the membrane and dividing the cytoplasm of cells into isolated spaces.

This is necessary to separate the many parallel reactions. The rough endoplasmic reticulum is distinguished (on its surface there are ribosomes on which protein is synthesized) and the smooth endoplasmic reticulum (lipids and carbohydrates are synthesized on its surface).

golgi apparatus(lamellar complex) is a stack of 5-20 flattened disk-shaped membrane cavities and microbubbles laced from them.

Its function is the transformation, accumulation, transport of substances entering it to various intracellular structures or outside the cell. The membranes of the Golgi apparatus are capable of forming lysosomes.

Lysosomes- membranous vesicles containing hydrolytic enzymes.

There are primary and secondary lysosomes. Primary lysosomes are microvesicles that detach from the cavities of the Golgi apparatus, surrounded by a single membrane and containing a set of hydrolytic enzymes. Secondary lysosomes are formed after the fusion of primary lysosomes with a substrate to be cleaved.

Secondary lysosomes include:

1. digestive vacuoles - are formed by the fusion of primary lysosomes with phagocytic and pinocytic vacuoles (digestive vacuoles of protozoa).

   Their function is the digestion of substances that enter the cell during endocytosis;

2. residual bodies contain undigested material. Their function is the accumulation of undigested substances and, usually, their removal to the outside through exocytosis;
3. autolysosomes - are formed by the fusion of primary lysosomes with spent organelles.

   Their function is the destruction of the spent parts of the cell or the whole cell (autolysis).

Vacuoles- fluid-filled membrane sacs in the cytoplasm of plant cells. They are formed from small vesicles that split off from the endoplasmic reticulum. The membrane of the vacuole is called the tonoplast, and the contents of the cavity are called cell sap. Cell sap contains reserve nutrients, pigment solutions, waste products, hydrolytic enzymes.

Vacuoles are involved in the regulation of water-salt metabolism, the creation of turgor pressure, the accumulation of reserve substances and the removal of toxic compounds from the exchange.

Peroxisomes- Membrane vesicles containing a set of enzymes. Peroxisome enzymes (catalase, etc.) neutralize toxic hydrogen peroxide (H2O2), which is formed as intermediate product in biochemical reactions, catalyzing its decomposition into water and oxygen.

Peroxisomes are also involved in lipid metabolism.

two-membrane cell organelles

In eukaryotic cells, there are organelles isolated from the cytoplasm by two membranes - these are mitochondria and plastids.

They have their own circular DNA molecule, small ribosomes and are able to divide. This was the basis for the emergence of the symbiotic theory of the origin of eukaryotes.

According to this theory, in the past, mitochondria and plastids were independent prokaryotes, which later switched to endosymbiosis with other cellular organisms.

Mitochondria- two-membrane organelles present in all eukaryotic cells. They can be rod-shaped, oval or rounded. The content of mitochondria (matrix) is limited from the cytoplasm by two membranes: outer smooth and inner, forming folds (cristae).

ATP molecules are formed in mitochondria. For this, the energy released during the oxidation of organic compounds is used.

plastids- two-membrane organelles, characteristic only for cells of photosynthetic eukaryotic organisms.

They have two membranes and a homogeneous substance inside - the stroma (matrix). Depending on the color, the following types of plastids are distinguished.

1. Chloroplasts are green plastids in which the process of photosynthesis takes place.

   The outer membrane is smooth; internal - forms a system of flat vesicles (thylakoids), which are collected in piles (granas). Thylakoid membranes contain green pigments of chlorophyll, as well as carotenoids;

2. chromoplasts - plastids containing carotenoid pigments, giving them a red, yellow and orange color.

   They give a bright color to flowers and fruits;

3. leukoplasts are unpigmented, colorless plastids. Contained in the cells of underground or unpainted parts of plants (roots, rhizomes, tubers). Able to accumulate reserve nutrients, primarily starch, lipids and proteins. Leukoplasts can turn into chloroplasts (for example, during the flowering of potato tubers) and rarely into chromoplasts (for example, when the root ripens in carrots), and chloroplasts into chromoplasts (for example, when fruits ripen).

Non-membrane organelles

These include ribosomes, microtubules, microfilaments, and the cell center.

Ribosomes- small organelles formed by two subunits: large and small.

They are made up of proteins and rRNA.

The small subunit contains one rRNA molecule and proteins, while the large subunit contains three rRNA molecules and proteins. Ribosomes can either be free in the cytoplasm or attached to the endoplasmic reticulum. Protein synthesis takes place on ribosomes. Proteins synthesized on ribosomes on the surface of the endoplasmic reticulum usually enter its cisterns, while those formed on free ribosomes remain in the hyaloplasm.

microtubules And microfilaments- filamentous structures, consisting of contractile proteins and determining the motor functions of the cell.

Microtubules look like long hollow cylinders, the walls of which are composed of proteins - tubulins. Microfilaments are even thinner, long, filamentous structures composed of actin and myosin proteins. Microtubules and microfilaments penetrate the entire cytoplasm of the cell, forming its cytoskeleton, causing cyclosis (cytoplasmic flow), intracellular movements of organelles, forming a division spindle, etc.

Microtubules organized in a certain way form centrioles of the cell center, basal bodies, cilia, flagella.

Cell center (centrosome) usually located near the nucleus, consists of two centrioles located perpendicular to each other. Each centriole has the form of a hollow cylinder, the wall of which is formed by nine triplets of microtubules (9 + 0).

Centrioles play important role in cell division, forming the spindle of division.

Cilia, flagella- organelles of movement, which are peculiar outgrowths of the cytoplasm of the cell, covered with a plasma membrane. At the base of the cilia and flagella are the basal bodies that serve as their support.

The basal body is a cylinder formed by nine triplets of microtubules (9 + 0). Basal bodies are able to restore cilia and flagella after their loss. The skeleton of the cilium and flagellum is also a cylinder, along the perimeter of which there are nine paired microtubules, and in the center - two single microtubules (9 + 2).

S. V. Kachnova

The structure of eukaryotic cells. The structure of the cell wall

Lesson type: combined.

Methods: verbal, visual, practical, problem-search.

Lesson Objectives

Educational: to deepen students' knowledge of the structure of eukaryotic cells, to teach how to apply them in practical classes.

Developing: to improve the ability of students to work with didactic material; develop students' thinking by offering tasks for comparing prokaryotic and eukaryotic cells, plant cells and animal cells with the identification of similar and distinctive features.

Equipment: poster "The structure of the cytoplasmic membrane"; task cards; handout (the structure of a prokaryotic cell, a typical plant cell, the structure of an animal cell).

Interdisciplinary connections: botany, zoology, human anatomy and physiology.

Lesson Plan

I.

Organizing time

Check readiness for the lesson.
Checking the list of students.
Presentation of the topic and objectives of the lesson.

II.

Learning new material

Division of organisms into pro- and eukaryotes

The shape of the cells is extremely diverse: some are rounded, others look like stars with many rays, others are elongated, etc. Cells are also different in size - from the smallest, hardly distinguishable in a light microscope, to those perfectly visible to the naked eye (for example, fish and frog eggs).

Any unfertilized egg, including giant fossilized dinosaur eggs that are kept in paleontological museums, were also once living cells. However, if we talk about the main elements of the internal structure, all cells are similar to each other.

prokaryotes(from Latin pro - before, before, instead of Greek karyon - nucleus) - these are organisms whose cells do not have a nucleus limited by a membrane, i.e.

all bacteria, including archaebacteria and cyanobacteria. The total number of species of prokaryotes is about 6000. All genetic information prokaryotic cell (genophore) is contained in a single circular DNA molecule. Mitochondria and chloroplasts are absent, and the functions of respiration or photosynthesis, which provide the cell with energy, are performed by the plasma membrane (Fig. 1). Prokaryotes reproduce without a pronounced sexual process by dividing in two. Prokaryotes are able to carry out a number of specific physiological processes: they fix molecular nitrogen, carry out lactic acid fermentation, decompose wood, and oxidize sulfur and iron.

After an introductory conversation, students consider the structure of a prokaryotic cell, comparing the main features of the structure with the types of eukaryotic cells (Fig.

eukaryotes- This higher organisms having a clearly defined nucleus, which is separated from the cytoplasm by a membrane (karyomembrane).

Eukaryotes include all higher animals and plants, as well as unicellular and multicellular algae, fungi and protozoa. Nuclear DNA in eukaryotes is enclosed in chromosomes. Eukaryotes have cellular organelles limited by membranes.

Differences between eukaryotes and prokaryotes

- Eukaryotes have a real nucleus: the genetic apparatus of a eukaryotic cell is protected by a shell similar to the shell of the cell itself.
– Organelles included in the cytoplasm are surrounded by a membrane.

The structure of plant and animal cells

The cell of any organism is a system. It consists of three interconnected parts: membrane, nucleus and cytoplasm.

In the study of botany, zoology and human anatomy, you have already become familiar with the structure various types cells. Let's briefly review this article.

Task 1. Determine from Figure 2 which organisms and types of tissues correspond to the cells under the numbers 1-12. What is the reason for their shape?

The structure and functions of organelles of plant and animal cells

Using figures 3 and 4 and using the Biological Encyclopedic Dictionary and textbook, students complete the table comparing animal and plant cells.

Table.

The structure and functions of organelles of plant and animal cells

cell organelles	The structure of organelles	Function	Presence of organelles in cells
plants	animals
Chloroplast	It is a type of plastid	Colors plants green for photosynthesis
leukoplast	The shell consists of two elementary membranes; internal, growing into the stroma, forms a few thylakoids	Synthesizes and accumulates starch, oils, proteins
Chromoplast	Plastids with yellow, orange and red color, the color is due to pigments - carotenoids	Red, yellow coloring autumn leaves, juicy fruits, etc.
	Occupies up to 90% of the volume of a mature cell, filled with cell sap	Maintenance of turgor, accumulation of reserve substances and metabolic products, regulation of osmotic pressure, etc.
microtubules	Composed of the protein tubulin, located near the plasma membrane	Participate in the deposition of cellulose on cell walls, the movement of various organelles in the cytoplasm. During cell division, microtubules form the basis of the division spindle structure.
Plasma membrane (CPM)	Consists of a lipid bilayer permeated with proteins immersed to various depths	Barrier, transport of substances, communication between cells
Smooth EPR	System of flat and branching tubules	Carries out the synthesis and release of lipids
Rough EPR	It got its name because of the many ribosomes on its surface.	Synthesis of proteins, their accumulation and transformation for release from the cell to the outside
	Surrounded by a double nuclear membrane with pores. The outer nuclear membrane forms a continuous structure with the ER membrane. Contains one or more nucleoli	Carrier of hereditary information, center of regulation of cell activity
cell wall	Composed of long cellulose molecules arranged in bundles called microfibrils	Outer frame, protective shell
Plasmodesmata	Tiny cytoplasmic channels that pierce cell walls	Unite protoplasts of adjacent cells
Mitochondria	The inner membrane of mitochondria forms numerous folds	ATP synthesis (energy storage)
golgi apparatus	Consists of a stack of flat sacs - cisterns, or dictyosomes	Synthesis of polysaccharides, formation of CPM and lysosomes
Lysosomes		intracellular digestion
Ribosomes	Composed of two unequal subunits large and small, into which they can dissociate	Site of protein biosynthesis
Cytoplasm	Consists of water with a large amount of dissolved substances containing glucose, proteins and ions	It contains other organelles of the cell and all processes of cellular metabolism are carried out.
Microfilaments	Actin fibers are usually arranged in bundles near the surface of cells	Involved in cell motility and reshaping
Centrioles	May be part of the mitotic apparatus of the cell. A diploid cell contains two pairs of centrioles	Participate in the process of cell division in animals; in zoospores of algae, mosses and in protozoa they form basal bodies of cilia
microvilli	protrusions of the plasma membrane	Increase the outer surface of the cell, microvilli together form the border of the cell

conclusions

The cell wall, plastids, and central vacuole are unique to plant cells.
2. Lysosomes, centrioles, microvilli are present mainly only in the cells of animal organisms.
3. All other organelles are characteristic of both plant and animal cells.

The structure of the cell membrane

The cell membrane is located outside the cell, delimiting the latter from the outer or internal environment organism.

It is based on the plasmalemma (cell membrane) and the carbohydrate-protein component.

Cell wall functions:

- maintains the shape of the cell and gives mechanical strength to the cell and the organism as a whole;
- protects the cell from mechanical damage and the ingress of harmful compounds into it;
- performs recognition of molecular signals;
- regulates the exchange of substances between the cell and the environment;
- carries out intercellular interaction in a multicellular organism.

Cell wall function:

- represents an external frame - a protective shell;
- provides transport of substances (water, salts, molecules of many organic substances pass through the cell wall).

The outer layer of animal cells, unlike the cell walls of plants, is very thin and elastic.

It is not visible under a light microscope and consists of a variety of polysaccharides and proteins. The surface layer of animal cells is called glycocalyx, it performs the function of a direct connection of animal cells with the external environment, with all the substances surrounding it, it does not play a supporting role.

Under the glycocalyx of the animal and cell wall of the plant cell, there is a plasma membrane that borders directly on the cytoplasm.

The plasma membrane contains proteins and lipids.

They are arranged in an orderly manner due to various chemical interactions with each other. Lipid molecules in the plasma membrane are arranged in two rows and form a continuous lipid bilayer. Protein molecules do not form a continuous layer, they are located in the lipid layer, plunging into it at different depths. Molecules of proteins and lipids are mobile.

Functions of the plasma membrane:

- forms a barrier that separates the internal contents of the cell from external environment;
- provides transport of substances;
- provides communication between cells in the tissues of multicellular organisms.

Entry of substances into the cell

The surface of the cell is not continuous.

In the cytoplasmic membrane there are numerous tiny holes - pores through which, with or without the help of special proteins, ions and small molecules can penetrate into the cell. In addition, some ions and small molecules can enter the cell directly through the membrane. The entry of the most important ions and molecules into the cell is not passive diffusion, but active transport, which requires energy. Transport of substances is selective. The selective permeability of a cell membrane is called semi-permeability.

By phagocytosis, large molecules of organic substances, such as proteins, polysaccharides, food particles, bacteria enter the cell. Phagocytosis is carried out with the participation of the plasma membrane. In the place where the surface of the cell comes into contact with a particle of some dense substance, the membrane flexes, forms a recess and surrounds the particle, which in the "membrane capsule" is immersed inside the cell.

A digestive vacuole is formed, and organic substances that have entered the cell are digested in it.

By phagocytosis, amoeba, ciliates, animal and human leukocytes feed. Leukocytes absorb bacteria, as well as a variety of solid particles that accidentally enter the body, thus protecting it from pathogenic bacteria. The cell wall of plants, bacteria and blue-green algae prevents phagocytosis, and therefore this pathway of substances entering the cell is not realized in them.

Liquid droplets containing various substances in a dissolved and suspended state also penetrate into the cell through the plasma membrane. This phenomenon was called pinocytosis.

The process of fluid absorption is similar to phagocytosis. A drop of liquid is immersed in the cytoplasm in a "membrane package". organic matter, which entered the cell along with water, begin to be digested under the influence of enzymes contained in the cytoplasm.

Pinocytosis is widespread in nature and is carried out by the cells of all animals.

III. Consolidation of the studied material

What two large groups are all organisms divided into according to the structure of the nucleus?
What organelles are found only in plant cells?
What organelles are found only in animal cells?
What is the difference between the structure of the cell wall of plants and animals?
What are the two ways substances enter the cell?
What is the importance of phagocytosis for animals?

Every living organism is made up of cells, many of which are able to move. In this article we will talk about the organoids of movement, their structure and functions.

Organelles of the movement of unicellular organisms

In modern biology, cells are divided into prokaryotes and eukaryotes. The former include representatives of the simplest organisms that contain one strand of DNA and do not have a nucleus (blue-green algae, viruses).

Eukaryotes have a nucleus and consist of a variety of organelles, one of which is the organelles of movement.

The organelles of the movement of unicellular organisms include cilia, flagella, filamentous formations - myofibrils, pseudopods. With their help, the cell can move freely.

Rice. 1. Varieties of organoids of movement.

Organelles of movement are also found in multicellular organisms. So, for example, in humans, the bronchial epithelium is covered with many cilia that move in exactly the same order. In this case, the so-called "wave" is formed, which can protect the respiratory tract from dust and foreign particles. And also flagella are present in spermatozoa (specialized cells of the male body that serve for reproduction).

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The motor function can also be carried out due to the contraction of microfibers (myonemes), which are located in the cytoplasm under the covers.

The structure and functions of the organelles of movement

Organelles of movement are outgrowths of the membrane, which reach 0.25 microns in diameter. In their structure, the flagella are much longer than the cilia.

The length of the sperm flagellum in some mammals can reach 100 microns, while the size of the cilia is up to 15 microns.

Despite such differences, the internal structure of these organelles is exactly the same. They are formed from microtubules, which are similar in structure to the centrioles of the cell center.

Motor movements are formed due to the sliding of microtubules among themselves, as a result of which they bend. At the base of these organelles is the basal body, which attaches them to the cellular cytoplasm. To ensure the work of the organelles of movement, the cell consumes the energy of ATP.

Rice. 2. The structure of the flagellum.

Some cells (amoebae, leukocytes) move due to pseudopodia, in other words, pseudopodia. However, unlike flagella and cilia, pseudopodia are temporary formations. They can disappear and reappear different places cytoplasm. Their functions include movement, as well as the capture of food and other particles.

Flagella consist of a filament, a hook, and a basal body. According to the number and location of these organelles on the surface of bacteria they are divided into:

• Monotrichous(one flagellum);
• amphitriches(one flagellum at different poles);
• lophotrichous(a bundle of formations at one or both poles);
• Peritrichi(many flagella located over the entire surface of the cell).

Rice. 3. Varieties of flagellates.

Among the functions performed by the organoids of movement are:

• ensuring the movement of a unicellular organism;
• the ability of muscles to contract;
• protective reaction of the respiratory tract from foreign particles;
• fluid advancement.

Flagellates play an important role in the circulation of substances in environment, many of them are good indicators of water pollution.

What have we learned?

One of the constituent elements of the cell are the organelles of movement. These include flagella and cilia, which are formed by microtubules. Their functions include ensuring the movement of a unicellular organism, the movement of fluids inside a multicellular organism.

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Organelles(organelles)- in cytology, permanent specialized structures in the cells of living organisms. Each organelle performs certain functions vital for the cell. The term "Organoids" is explained by the comparison of these components of the cell with the organs of a multicellular organism. Organelles contrast with the temporary inclusions of the cell, which appear and disappear in the process of metabolism.

Sometimes only permanent cell structures located in its cytoplasm are considered organelles. Often the nucleus and intranuclear structures (for example, the nucleolus) are not called organelles. The cell membrane, cilia and flagella are also usually not classified as organelles.

Receptors and other small, molecular level structures are not called organelles. The boundary between molecules and organelles is not very clear. Thus, ribosomes, which are usually unambiguously referred to as organelles, can also be considered as a complex molecular complex. Elements of the cytoskeleton (microtubules, thick filaments of striated muscles, etc.) are usually not classified as organelles.

In many ways, the set of organoids listed in the training manuals is determined by tradition.

Cellular organelles (having a membrane structure)

Name	animal cage	plant cell
Core		System of genetic determination and regulation of protein metabolism
Endoplasmic reticulum granular (ER)		Synthesis of hormones, enzymes, plasma proteins, membranes; segregation (isolation) of synthesized proteins; formation of membranes of the vacuolar system, plasmalemma, synthesis of phospholipids
Smooth endoplasmic reticulum (EPS)		Metabolism of lipids and some intracellular polysaccharides
Golgi lamellar complex	synthesis of polysaccharides	Secretion, segregation and accumulation of products synthesized in EPS, synthesis of polysaccharides
Lysosomes primary	Hydrolysis of biopolymers	Hydrolysis of biopolymers
Lysosomes secondary (see vacuole)		The result of phagocytosis, pinocytosis, transmembrane transport of substances
Autolysosome		Autolysis of cellular components
Peroxisomes	Oxidation of amino acids, formation of peroxides	Oxidation of amino acids, formation of peroxides, protective function
Mitochondria	ATP synthesis	ATP synthesis
kinetoplast		Complex function: movement and energy supply of movement
Plastids: chloroplasts chromatophores leucoplasts chromoplasts		Photosynthesis, synthesis and hydrolysis of secondary starch (amyloplasts); oils (elaioplasts); proteins (proteinoplasts, proteoplasts)
Vacuole	intracellular digestion	Accumulation of water and nutrients

Cellular organelles (having a non-membrane structure)

Name	animal cage	plant cell
nucleolus		Site of ribosomal RNA formation
Centrioles (centrosomes)		Spindle formation
Ribosomes	protein synthesis	protein synthesis
microtubules		Cytoskeleton, participation in the transport of substances and organelles
Micro-filaments		Contractile elements of the cytoskeleton, cell mobility, intracellular movement of substances
microfibrils		Contractile function of the cell and intracellular movement of organelles
Flagella	Movement organs	Movement organs
Cilia	Increased suction surface	Organs of movement, protection
Dictyosomes, Desmosomes	High contact membranes	Organ of intercellular contact

eukaryotic organelles

(general information)

organelle	main function	Structure	organisms	Notes
Chloroplast (Plastids)	photosynthesis	two-membrane	plants, protista	have their own DNA; suggest that chloroplasts arose from cyanobacteria as a result of symbiogenesis
Endoplasmic reticulum	translation and folding of new proteins (granular endoplasmic reticulum), lipid synthesis (agranular endoplasmic reticulum)	single-membrane	all eukaryotes	on the surface of the granular endoplasmic reticulum there is a large number of ribosomes, folded like a bag; agranular endoplasmic reticulum coiled into tubules
golgi apparatus	sorting and converting proteins	single-membrane	All eukaryotes	asymmetric - cisterns located closer to the cell nucleus contain the least mature proteins, and vesicles containing fully mature proteins bud off from cisterns located farther from the nucleus
Mitochondria	energy	two-membrane	most eukaryotes	have their own mitochondrial DNA; suggest that mitochondria arose as a result of symbiogenesis
Vacuole	reserve, maintaining homeostasis, in plant cells - maintaining the shape of the cell (turgor)	single membrane	eukaryotes, more pronounced in plants
Core	DNA storage, RNA transcription	double membrane	all eukaryotes	contains the bulk of the genome
Ribosomes	protein synthesis based on messenger RNAs using transfer RNAs	RNA/protein	eukaryotes, prokaryotes
Vesicles	store or transport nutrients	single membrane	all eukaryotes
Lysosomes	small labile formations containing enzymes, in particular hydrolases, taking part in the processes of digestion of phagocytosed food and autolysis (self-dissolution of organelles)	single membrane	most eukaryotes
Centrioles (cell center)	Center for the organization of the cytoskeleton. Necessary for the process of cell division (evenly distributes chromosomes)	non-membrane	eukaryotes
Melanosome	pigment storage	single membrane	animals
myofibrils	contraction of muscle fibers	intricately organized bundle of protein filaments	animals

It is assumed that mitochondria And plastids- these are former symbionts of cells containing them, once independent prokaryotes

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General purpose organelles

Three groups can be distinguished among them:

1 - organelles involved in the synthesis of substances;

2 - organelles with a protective digestive function;

3 - organelles that provide the cell with energy.

4 - organelles involved in cell division and movement.

In any cell, the synthesis of substances characteristic of it is carried out, which are either building material for newly formed structures instead of worn ones, or enzymes involved in biochemical reactions, or secrets secreted from gland cells.

The starting products for synthesis are substances formed during the decay of cellular structures, but mainly absorbed by the cell from the outside. At the same time, those of them that are whole molecules of proteins, fats and carbohydrates, previously adsorbed on the cell surface and entered the cytoplasm, are broken down by enzymes into their constituent parts. An active role in the synthesis of cellular substances belongs to the endoplasmic reticulum and ribosomes.

Endoplasmic reticulum (ER)

The endoplasmic reticulum (endoplasmic reticulum) was first discovered by the American scientist Porter in 1945 when electron microscopy cultures of connective tissue cells - fibroblasts - and called the endoplasmic reticulum. There are two types of EPS: smooth (agranular) and rough (granular). Both of them are formed by cisterns or channels, which are limited by a membrane, 6-7 nm thick. On the outer surface of the membrane of the rough EPS there are ribonucleoprotein granules - ribosomes that are absent on the surface of the membranes of the smooth network. Both types of EPS are usually in a direct structural relationship due to the direct transition of EPS membranes of one type to EPS membranes of another type, and the contents of the channels and cisterns of these types of EPS are not delimited by special structures. However, both types of EPS are differentiated specific intracellular organelles specialized for the implementation of different functions.

The structure of a smooth EPS. It is represented by tubules with a diameter of 50–100 nm, which on ultrathin sections look like paired membranes (tubules) or sacs. The membranes of the smooth cytoplasmic reticulum have much in common with other cell membranes. Their structure is based on a lipoprotein complex with a significant content of lipids (up to 50%), The thickness of each membrane is about 6-7 nm. Agranular EPS is constantly present in the cells of the liver, glomerular and fascicular zones of the adrenal glands, as well as in cardiac myocytes and muscle fibers of skeletal muscles. The agranular network, as a rule, is determined in places of accumulation of glycogen or lipid inclusions.

Smooth EPS function associated mainly with carbohydrate and fat metabolism. It is believed that it is involved in the synthesis of lipids and the breakdown of glycogen, while protecting the resulting glucose from the action of glycolytic enzymes.

Finally, the importance of the smooth endoplasmic reticulum as an intracellular impulse conduction system, in particular, in muscle fibers, where it lies along myofibrils (protein filaments capable of contracting when stimulated), becomes more and more obvious. Smooth ER can transport and accumulate substances, perform the function of detoxifying harmful metabolic products. In striated muscle tissue, smooth ER plays the role of a reservoir of calcium ions, and its membranes contain powerful calcium pumps that can eject in hundredths of a second large quantities ions into the cytoplasm or, conversely, transport them into the cavity of these channels. ER in adrenal cells is specialized for the synthesis of precursors of steroid hormones.

Structure of EPS of granular type. It consists of a branched system of tubules or flat sacs bounded by lipoprotein membranes, on the surface of which ribosomes are located. It is found in almost all cells, but is most strongly developed in cells with high level protein metabolism, for example, in cells endocrine system, pancreas, liver, salivary glands, neurons of the central nervous system etc. Thus, in secretory cells synthesizing proteins for export, granular ER occupies the bulk of the cytoplasm.

After cell death, the granular EPS is destroyed much later than the agranular one.

EPS function of granular type, primarily associated with providing protein synthesis, intracellular transport And initial post-translational modification of proteins synthesized on attached ribosomes. It is proved that on the surface of granular EPS, the synthesis of the series simple substances protein nature. Synthesized substances are able to enter the ER space and move inside the cell. It has been established that EPS membranes can pass into the outer membrane of the nuclear envelope. As a result, the EPS space can communicate with the perinuclear space located between the outer and inner membranes of the nuclear envelope. Sometimes granular ER can play the role of a reservoir for storing reserve nutrients.

In addition, the most important function of the EPS membrane is its ability to limit homogeneous areas of the cytoplasm and the substances they contain. Such a phenomenon is called compartmentalization cytoplasm.

EPS biogenesis. This issue is of great interest, since the EPS is a dynamic structure that undergoes significant changes due to functional fluctuations inherent in cells. So, for example, during starvation of the body, when protein synthesis decreases and liver glycogen is intensively consumed, the mass of the granular network in its cells decreases and the volume of the agranular network increases sharply.

Currently, there are several points of view on the sources of the formation of EPS membranes: 1 - the formation of membranes with the participation of the nuclear membrane; 2 - the formation of new membranes in the existing granular ER, which are only secondarily transformed into a system of smooth ER; 3 - the formation of membranes anew from the proteins and lipids present in the cytoplasm.

Ribosomes

Ribosomes are ribonucleoprotein granules in which the synthesis of proteins characteristic of a given organism is carried out. In the cytoplasm of cells, they lie either on the surface of the membrane of the granular cytoplasmic reticulum ( linked ribosomes), or are located freely in the cytoplasm ( free ribosomes), or are part of mitochondria ( mitochondrial ribosomes). Single cytoplasmic ribosomes are about 10-25 nm in size, mitochondrial ribosomes are smaller.

The structure of the ribosome. Research done with electron microscope showed that the ribosome contains a messenger RNA (mRNA), two ribosomal subunits (large and small), and a transfer RNA (tRNA). Each subunit is built from ribosomal RNA (rRNA) and protein in a 1:1 ratio. The formation of ribosomes occurs in the cytoplasm of the cell as follows: the small subunit is first attached to the mRNA molecule, then the tRNA, and finally the large subunit. A complex complex is formed from closely adjacent macromolecules. There are also data on the presence of lipids, ions and enzymes in ribosomes. The connection of individual ribosomes with ER membranes is carried out by large subunits.

carried out in ribosomes synthesis of various proteins: in free ribosomes - proteins necessary for the cell itself, in membrane-bound ribosomes - proteins that go for "export", that is, secreted by the cell. Using the method of electron microscopy and the introduction of labeled amino acids, it was possible to establish that in ribosomes associated with membranes, protein synthesis occurs approximately 20 times faster than in free ribosomes. It is believed that on the ribosomes of the granular ER, proteins are synthesized in 2-3 minutes, and after 10 minutes they move into the lumen of the tubules of the endoplasmic reticulum.

During intensive protein synthesis, individual ribosomes are combined with the help of messenger RNA, as if strung on its long molecule, into small groups called polysomes, or polyribosomes. The number of ribosomes in a polysome can vary from 5-7 to 70-80 or more, depending on the size of the protein molecule.

Ribosome biogenesis. The number of ribosomes in the cytoplasm is subject to significant fluctuations, reflecting various functional states of cells. The nucleolus plays a key role in the formation of ribosomes. Direct evidence that the nucleolus is responsible for rRNA synthesis came in 1964 when it was discovered that rRNA synthesis does not occur in mutant cells lacking nucleoli. Synthesis of rRNA is encoded by ribosomal DNA, which is localized to specific regions of chromosomes - nucleolar regions (NORs). Ribosomal proteins (there are more than 50 types) are synthesized in the cytoplasm and then transported to the nucleolus, where they combine with rRNA. Thus, large and small subunits of ribosomes are formed in the nucleoli, which are subsequently transported from the nucleus to the cytoplasm of the cell.

Golgi lamellar complex

In 1898, the Italian scientist Golgi, using the silver nitrate impregnation method, discovered in nerve cells spinal ganglion structures consisting of plates and vesicles. This is the lamellar complex that wore for a long time Golgi's name.

A serious contribution to understanding the significance of the lamellar complex was made by the Soviet scientist cytologist D.N. Nasonov (1930), who established the essential role of this organelle in secretion processes.

The structure of the lamellar complex. The basis of the structure of the lamellar complex, as well as the basis of the structure of most cell organelles, are lipoprotein membranes, thick. Electron microscopy data showed that the lamellar complex is a heterogeneous formation. The central, most typical and permanent structure of the Golgi apparatus is a system of flattened cisterns that make up a stack or column of adjacent oval or rounded formations (dictyosome). In the peripheral part of the cisterns (in typical cases), the vacuolar part of the Golgi complex is formed, consisting of membrane-limited vesicles of different sizes.

In more complex variants of the organization of the Golgi complex, a complex system of tubular intertwining structures limited by membranes develops on the periphery of the cisterns, from which peripheral vesicles and vacuoles are laced.

On the periphery of the Golgi apparatus there are clusters of polyribosomes. It has been shown that they synthesize a number of enzymes specific for the membranes of the Golgi apparatus. A close spatial connection of the Golgi complex with the EPS membranes and the nuclear envelope is characteristic. Some authors have found a direct transition of the tubules of the granular EPS into the lamellar complex.

In a living cell, the lamellar complex is located near the nucleus. The shape of the lamellar complex varies depending on functional state cells.

Functions of the plate complex been involved for a long time in the design of secretory granules, in secretion And transport. The Golgi complex is a packaging "workshop" in the cell, a condensation membrane, concentrating substances produced by the cell in the form of drops or granules. However, in Lately it has been established that it also performs a number of other functions; happens in it dehydration(dehydration) of protein products of secretory granules, segregation(enlargement) of protein molecules, synthesis of complex complex compounds: glycoproteins, glycolipids, mucopolysaccharides, mature immunoglobulin molecules, etc.

It is believed that the plate complex gives rise to small bubbles, which play the role of transport structures that connect the lamellar complex with the cytoplasmic reticulum and cell membrane. It is also believed that he takes part in the formation of primary lysosomes. The Golgi complex is involved in the formation of the sperm acrosome. From the tanks of the Golgi apparatus, as well as from the EPS, peroxisomes.

Biogenesis of the lamellar complex. According to existing assumptions, the lamellar complex can arise in various ways: 1 - due to fragmentation (division) of its elements, 2 - from granular ER membranes, 3 - from microbubbles formed on the outer surface of the nuclear membrane, 4 - can be formed de novo.

microtubules

They were first observed in axoplasm squeezed out of myelinated nerve fibers. Cytoplasmic microtubules are characterized by constant dimensions and amazing straightness. Their diameter is about 24 nm, length is several microns. In cross section, they look like a ring. This configuration is formed by a dense wall and a light central area.

The microtubule wall consists of separate linear or helical filamentous structures with a diameter of about 5 nm, which, in turn, consist of protein subunits. On a cross section of a microtubule, there are about 13 subunits. Sometimes dense strands or rods are found in the central part of some microtubules.

Functions of microtubules. In cilia, flagella, the mitotic spindle and in the cytoplasm of protozoa capable of contracting the cell body, the functions of microtubules are associated with a reduction.

Microtubules make up about 10% of the protein spindle-forming division. It is they that cause the double refraction of the spindle and the rays of the star. During cytokinesis, peristaltic waves are observed in the bridge connecting two daughter cells (and containing numerous microtubules).

Microtubules are credited with the role of a scaffold (cytoskeleton), the function of which is in creating and maintaining the shape of the cell, as well as redistributing its contents.

Microtubules appear to be involved during intracellular microcirculation transport of small molecules within the cell. To do this, they form and delimit a kind of channels in the cytoplasm.

Microtubules may play a role in local cell shape changes that occur during cellular differentiation during embryonic development. A pronounced elongation of the spermatid nucleus is accompanied by the appearance of microtubules strictly ordered according to their location, which cover the nucleus in a direction perpendicular to its axis; these microtubules form a double helix around the nucleus.