The structure and life of protozoa. What is the shape of the amoeba nucleus?

Amoeba is a genus of single-celled eukaryotic organisms (they belong to the simplest). They are considered animal-like because they feed heterotrophically.

The structure of amoebas is usually considered on the example of a typical representative - the common amoeba (Proteus amoeba).

Amoeba ordinary (hereinafter amoeba) lives at the bottom of freshwater reservoirs with polluted water. Its size ranges from 0.2 mm to 0.5 mm. In appearance, the amoeba looks like a shapeless, colorless lump that can change its shape.

The amoeba cell does not have a hard shell. It forms protrusions and invaginations. Protrusions (cytoplasmic outgrowths) are called pseudopods or pseudopodia. Thanks to them, the amoeba can move slowly, as if flowing from place to place, and also capture food. The formation of prolegs and the movement of the amoeba occurs due to the movement of the cytoplasm, which gradually flows into the protrusion.

Although the amoeba is a unicellular organism and there can be no talk of organs and their systems, it is characterized by almost all the life processes characteristic of multicellular animals. The amoeba feeds, breathes, releases substances, and reproduces.

The amoeba cytoplasm is not homogeneous. A more transparent and dense outer layer is isolated ( eqtplasma) and a more granular and fluid inner layer of the cytoplasm ( endoplasm).

In the cytoplasm of the amoeba there are various organelles, the nucleus, as well as the digestive and contractile vacuoles.

The amoeba feeds on various unicellular organisms and organic residues. Food is wrapped around the pseudopods and is inside the cell, formed digestiveand Ivacuole. It receives various enzymes that break down nutrients. Those that the amoeba needs then enter the cytoplasm. Unnecessary food residues remain in the vacuole, which approaches the surface of the cell and everything is thrown out of it.

The "organ" of excretion in the amoeba is contractile vacuole. It receives excess water, unnecessary and harmful substances from the cytoplasm. The filled contractile vacuole periodically approaches the cytoplasmic membrane of the amoeba and pushes its contents out.

The amoeba breathes the entire surface of the body. Oxygen comes into it from water, carbon dioxide comes out of it. The process of respiration consists in the oxidation of organic substances in mitochondria with oxygen. As a result, energy is released, which is stored in ATP, and water and carbon dioxide are also formed. The energy stored in ATP is then used for various life processes.

For the amoeba, only asexual reproduction is described by dividing in two. Only large, i.e. grown, individuals divide. First, the nucleus divides, after which the amoeba cell divides by constriction. That daughter cell that does not receive a contractile vacuole forms one subsequently.

With the onset of cold weather or drought, the amoeba forms cyst. Cysts have a dense shell that performs a protective function. They are quite light and can be carried by the wind over long distances.

The amoeba is able to respond to light (creeps away from it), mechanical irritation, the presence of certain substances in the water.

The common amoeba (kingdom Animals, subkingdom Protozoa) has another name - Proteus, and is a representative of the Sarcode free-living class. It has a primitive structure and organization, moves with the help of temporary outgrowths of the cytoplasm, often referred to as pseudopods. Proteus consists of only one cell, but this cell is a complete independent organism.

Habitat

The structure of an ordinary amoeba

Amoeba ordinary - an organism consisting of one cell leading an independent existence. The body of the amoeba is a semi-liquid lump, 0.2-0.7 mm in size. Large individuals can be seen not only through a microscope, but also with an ordinary magnifying glass. The entire surface of the body is covered with cytoplasm, which covers the nucleus pulposus. During the movement, the cytoplasm constantly changes its shape. Stretching in one direction or the other, the cell forms processes, thanks to which it moves and feeds. It can push off algae and other objects with the help of pseudopods. So, in order to move, the amoeba stretches the pseudopod in the right direction, and then flows into it. The speed of movement is about 10 mm per hour.

The proteus does not have a skeleton, which allows it to take any form and change it as needed. The respiration of the common amoeba is carried out by the entire surface of the body; there is no special organ responsible for the supply of oxygen. During movement and feeding, the amoeba captures a lot of water. Excess fluid is excreted by a contractile vacuole that bursts to expel water and then re-forms. The amoeba has no special sense organs. But she tries to hide from direct sunlight, is sensitive to mechanical stimuli and some chemicals.

Nutrition

Proteus feeds on unicellular algae, rotting residues, bacteria and other small organisms, which it captures with its pseudopods and draws into itself so that the food is inside the body. A special vacuole is immediately formed here, where the digestive juice is secreted. Amoeba nutrition can occur anywhere in the cell. At the same time, several pseudopods can capture food, then the digestion of food occurs immediately in several parts of the amoeba. Nutrients enter the cytoplasm and go to build the body of the amoeba. Particles of bacteria or algae are digested, and the remains of vital activity are immediately removed to the outside. The common amoeba is capable of throwing out unnecessary substances on any part of its body.

reproduction

Reproduction of the common amoeba occurs by dividing one organism into two. When the cell has grown enough, a second nucleus is formed in it. This serves as a signal to divide. The amoeba stretches out, and the nuclei diverge on opposite sides. Approximately in the middle there is a constriction. Then the cytoplasm in this place bursts, so there are two separate organisms. Each of them contains a nucleus. The contractile vacuole remains in one of the amoebas, and a new one arises in the other. During the day, the amoeba can divide several times. Reproduction occurs in the warm season.

Cyst formation

With the onset of cold weather, the amoeba stops eating. Its pseudopods are retracted into the body, which takes the form of a ball. A special protective film is formed on the entire surface - a cyst (of protein origin). Inside the cyst, the body is in hibernation, does not dry out and does not freeze. In this state, the amoeba remains until the onset of favorable conditions. When the reservoir dries up, the cysts can be carried by the wind over long distances. In this way, amoeba settle in other water bodies. With the onset of heat and suitable humidity, the amoeba leaves the cyst, releases pseudopods and begins to feed and multiply.

The place of the amoeba in wildlife

The simplest organisms are a necessary link in any ecosystem. The importance of the common amoeba lies in its ability to regulate the number of bacteria and pathogens on which it feeds. The simplest unicellular organisms eat decaying organic remains, maintaining the biological balance of water bodies. In addition, the common amoeba is food for small fish, crustaceans, and insects. And those, in turn, are eaten by larger fish and freshwater animals. These same simple organisms serve as objects of scientific research. Large accumulations of unicellular organisms, including the common amoeba, participated in the formation of limestone, chalk deposits.

Amoeba dysentery

There are several varieties of protozoan amoebas. The most dangerous for humans is the dysenteric amoeba. It differs from the ordinary one in shorter pseudopods. Once in the human body, the dysenteric amoeba settles in the intestines, feeds on blood, tissues, forms ulcers and causes intestinal dysentery.

Among the simplest organisms, the amoeba is considered the most primitive. Bacteria are microscopic in size and are single-celled creatures.

Amoeba is the simplest single-celled creature

Amoeba - what is it?

Amoeba (rhizome)- the lowest rank of living beings. What is it - a bacterium or an animal? The microorganism belongs to the simplest unicellular animals, has tiny dimensions (from 0.2 to 0.5 mm), the shape of the body changes all the time depending on external conditions. Single-celled creatures, like more complex animals, use oxygen for breathing, and release carbon dioxide into the external environment.

Kinds

Under adverse conditions (temperature fluctuations, ponds drying up, air currents), it goes into sleep mode, transforming into a cyst

Amoebas enter the human or animal body in the form of a cyst, which is protected by a strong two-layer membrane. Infection occurs through food (poorly washed fruits and vegetables), contaminated water, dirty hands.

Structure

The amoeba does not have a skeleton, a mouth, lungs and gills.

Its structure is made up of organelles:

• big core;
• cytoplasm, clearly divided into two zones - ectoplasm and endoplasm;
• pseudopodia (false legs with which the cell moves);
• digestive vacuole;
• contractile vacuole (removes excess water and food from the body of the amoeba).

What an amoeba looks like and what it consists of is shown in the photo.

Amoeba has a simple structure

Nutrition

The rhizopod feeds on pseudopodia. The process of taking in solid food is called phagocytosis. The capture of food is part of the main functions of the false legs: they wrap around edible particles, which helps the latter to get into the nutrient vacuole, where the membrane envelops them. Gradually, digestion occurs, the excess of which exits the contracting vacuole during the movement of the amoeba.

The process of capturing food by an amoeba

reproduction

Amoeba can only reproduce asexually. Having reached maturity, the cell begins to divide, which results in 2 daughter organisms.

How they reproduce:

• change in the core (first it stretches, then it lengthens, as a result of which it is pulled in the middle);
• division of the nucleus into two halves (formation of two independent nuclei);
• the division of the amoeba itself into two new cells, each of which has its own nucleus.

Amoeba reproduce asexually

During the appearance of a daughter microorganism, the formation of organelles missing for a new cell occurs. In 24 hours, an amoeba can go through the process of binary fission several times.

Life cycle

The amoeba has a simple cycle of existence. In a favorable environment, cells develop, grow and divide asexually. With the deterioration of the conditions of existence, the amoeba "freeze", thereby forming cysts. Once in the body of a person, animal, in water bodies or moist soil, microorganisms come to life, are released from the protective shell and begin to actively multiply.

When the environmental conditions deteriorate, the amoeba becomes covered with a protective shell (cyst)

Amoebiasis symptoms

Symptoms of amoebiasis largely depend on the type of disease:

1. Intestinal amoebiasis (dysentery amoebic colitis, amoebic dysentery). Characteristic symptoms: copious diarrhea streaked with blood, mucus and pus. As the disease develops, negative manifestations increase in the form of fever, chills, vomiting, and loss of appetite. During bowel movements, cramping pains in the lower abdomen are possible, which are less pronounced in a calm state.
2. Extraintestinal type of disease - occurs as a complication of intestinal amoebiasis. Most often affects the liver (abscess or amoebic hepatitis). Symptoms: an increase in the affected organ, pain in the right hypochondrium, the appearance of jaundice, high temperature (up to 40 degrees).

When amoebas damage the liver, pain appears in the right hypochondrium

Amebiasis has a mild course (fever, diarrhea, yellowness on the skin) and manifests itself already in the later stages of the disease in the form of a breakthrough of purulent formations (peritonitis). This threatens to damage the lungs, brain, genitourinary system.

Diagnostics

The basis for the diagnosis of amoebiasis is 2 main methods:

• bacteriological analysis of biological material (cysts are looked for in feces);
• endoscopic examination of the rectum (detection of the degree of damage to the intestinal mucosa).

Only after confirming the diagnosis, the specialist prescribes the necessary treatment, taking into account all the features and severity of the disease.

An endoscopic examination is used to determine the degree of damage to the rectum.

Amoebiasis treatment

Drugs that adversely affect amoebas are divided into 2 main groups:

• contact (translucent) - Clefamid, Paromomycin, Etofamide - are used for asymptomatic amoebiasis, as well as for the prevention of relapses;
• tissue - Tinidazole, Ornidazole, Metronidazole - are prescribed for intestinal amoebiasis, as well as in the treatment of abscesses in the liver, lungs, and brain.

An intestinal disease caused by amoebas responds well to therapy and is almost completely cured in the early stages of the pathology.

Metronidazole helps with intestinal amoebiasis

Prevention

Infection with protozoa can be prevented by following simple preventive measures:

• use only boiled water (boil for at least 10 minutes);
• wash fruits and vegetables well before use;
• make sure that flies do not sit on food (cover with a protective film);
• adhere to the rules of personal hygiene (wash hands after using the toilet, before eating, after visiting public places and walking on the street);
• do not fertilize the beds with human feces.

It is important to have regular check-ups and not to ignore any unpleasant symptoms. This is the only way to protect yourself from a serious illness.

Amoeba are the simplest animals that consist of one cell. Among primitive microorganisms there is a dangerous species - dysenteric amoeba (not to be confused with malaria pathogens), which causes a dangerous intestinal disease amoebiasis. If the pathology is not detected in time, it can lead to severe complications in the liver, lungs and even the brain. Prevention and timely access to a specialist make it possible to prevent dangerous consequences.

The sub-kingdom Unicellular includes animals whose body consists of only one cell, for the most part microscopic in size, but with all the functions inherent in the body. Physiologically, this cell represents a whole independent organism.

The two main components of the body of unicellular organisms are the cytoplasm and the nucleus (one or more). The cytoplasm is surrounded by an outer membrane. It has two layers: the outer (lighter and denser) - ectoplasm - and the inner - endoplasm. The endoplasm contains cellular organelles: mitochondria, endoplasmic reticulum, ribosomes, elements of the Golgi apparatus, various supporting and contractile fibers, contractile and digestive vacuoles, etc.

Habitat and external structure of the common amoeba

The simplest lives in water. It can be lake water, a dew drop, soil moisture, and even water inside us. The surface of their body is very delicate and dries instantly without water. Outwardly, the amoeba looks like a grayish gelatinous lump (0.2-05 mm), which does not have a permanent shape.

Motion

Amoeba "flows" along the bottom. Outgrowths that change their shape are constantly formed on the body - pseudopodia (pseudopodia). The cytoplasm gradually overflows into one of these protrusions, the false leg attaches to the substrate at several points, and movement occurs.

Internal structure

The internal structure of the amoeba

Nutrition

When moving, the amoeba encounters unicellular algae, bacteria, small unicellular organisms, “flows around” them and includes them in the cytoplasm, forming a digestive vacuole.

amoeba nutrition

Enzymes that break down proteins, carbohydrates and lipids enter the digestive vacuole, and intracellular digestion occurs. Food is digested and absorbed into the cytoplasm. The method of capturing food with the help of false legs is called phagocytosis.

Breath

Oxygen is used for cellular respiration. When it becomes less than in the external environment, new molecules pass into the cell.

amoeba breath

Molecules of carbon dioxide and harmful substances accumulated as a result of vital activity, on the contrary, go outside.

Selection

The digestive vacuole approaches the cell membrane and opens outward to throw out undigested residues anywhere in the body. The fluid enters the body of the amoeba through the resulting thin tubular channels, by pinocytosis. Contractile vacuoles are involved in pumping out excess water from the body. They gradually fill up, and every 5-10 minutes they are sharply reduced and push the water out. Vacuoles can occur anywhere in the cell.

reproduction

Amoeba reproduce only asexually.

amoeba reproduction

The grown amoeba begins to reproduce. It occurs through cell division. Prior to cell division, the nucleus doubles up so that each daughter cell receives its own copy of hereditary information (1). Reproduction begins with a change in the nucleus. It stretches (2), and then gradually lengthens (3,4) and is pulled in the middle. The transverse groove is divided into two halves, which diverge in different directions - two new nuclei are formed. The body of the amoeba is divided into two parts by constriction and two new amoeba are formed. Each of them gets one core (5). During division, the formation of missing organelles occurs.

During the day, division can be repeated several times.

asexual reproduction is a simple and quick way to increase the number of your descendants. This method of reproduction does not differ from cell division during the growth of the body of a multicellular organism. The difference is that the daughter cells of a unicellular organism diverge as independent ones.

Reaction to irritation

Amoeba has irritability - the ability to feel and respond to signals from the external environment. Crawling on objects, it distinguishes edible from inedible and captures them with pseudopods. She crawls and hides from the bright light (1)

mechanical irritations and increased concentrations of harmful substances (2).

This behavior, consisting in moving towards or away from the stimulus, is called taxis.

sexual process

Is absent.

Experiencing Adverse Conditions

A unicellular animal is very sensitive to environmental changes.

Under unfavorable conditions (when the reservoir dries up, during the cold season), amoeba draw in pseudopodia. A significant amount of water and substances are released onto the surface of the body from the cytoplasm, which form a strong double membrane. There is a transition to a resting state - a cyst (1). In the cyst, life processes are suspended.

Cysts carried by the wind contribute to the dispersal of the amoeba.

When favorable conditions occur, the amoeba leaves the cyst shell. It releases pseudopodia and becomes active (2-3).

Another form of protection is the ability to regenerate (recovery). A damaged cell can complete its destroyed part, but only if the nucleus is preserved, since all information about the structure is stored there.

Amoeba life cycle

The life cycle of an amoeba is simple. The cell grows, develops (1) and divides asexually (2). In bad conditions, any organism can "temporarily die" - turn into a cyst (3). When conditions improve, it “comes back to life” and multiplies intensively.

Habitat "Amoeba ordinary"

The common amoeba is found in the mud at the bottom of ponds with polluted water. It looks like a small (0.2-0.5 mm), colorless gelatinous lump, barely visible to the naked eye, constantly changing its shape ("amoeba" means "changeable"). It is possible to consider the details of the amoeba structure only under a microscope.

The structure and movement of the "Amoeba ordinary"

The body of the amoeba consists of a semi-liquid cytoplasm with a small bubble-like nucleus enclosed inside it. The amoeba consists of one cell, but this cell is a whole organism leading an independent existence.
The cytoplasm of the cell is in constant motion. If the current of the cytoplasm rushes to one point on the surface of the amoeba, a protrusion appears on its body in this place. It increases, becomes an outgrowth of the body - a pseudopod, the cytoplasm flows into it, and the amoeba moves in this way. Amoeba and other protozoans capable of forming pseudopods are classified as rhizopods. They got this name for the external resemblance of the pseudopods to the roots of plants.

Nutrition "Ameba ordinary"

An amoeba can simultaneously form several pseudopods, and then they surround food - bacteria, algae, and other protozoa. Digestive juice is secreted from the cytoplasm surrounding the prey. A vesicle is formed - a digestive vacuole.
Digestive juice dissolves some of the substances that make up food and digests them. As a result of digestion, nutrients are formed that seep from the vacuole into the cytoplasm and go to build the body of the amoeba. Undissolved residues are thrown out anywhere in the body of the amoeba.

Breath "Ameba ordinary"

The amoeba breathes oxygen dissolved in water, which penetrates into its cytoplasm through the entire surface of the body. With the participation of oxygen, complex food substances of the cytoplasm are decomposed into simpler ones. In this case, the energy necessary for the life of the body is released.

Isolation of harmful substances of vital activity and excess water "Amoeba ordinary"

Harmful substances are removed from the body of the amoeba through the surface of its body, as well as through a special vial - contractile vacuole. The water surrounding the amoeba constantly penetrates into the cytoplasm, liquefying it. The excess of this water with harmful substances gradually fills the vacuole. From time to time the contents of the vacuole are thrown out.
So, from the environment, food, water, oxygen enter the body of the amoeba. As a result of the life of the amoeba, they undergo changes. Digested food serves as material for building the body of the amoeba. The substances harmful to the amoeba are removed outside. going on amoeba metabolism. Not only amoeba, but also all other living organisms cannot exist without metabolism both inside their body and with the environment.

Reproduction "Amoeba ordinary"

The nutrition of the amoeba leads to the growth of its body. The grown amoeba begins to reproduce. Reproduction begins with a change in the nucleus. It is stretched, the transverse groove is divided into two halves, which diverge in different directions - two new nuclei are formed. The body of the amoeba is divided into two parts by a constriction. Each of them gets one nucleus. The cytoplasm between both parts is torn, and two new amoebas are formed. The contractile vacuole remains in one of them, while in the other it reappears. So, the amoeba reproduces by dividing in two. During the day, division can be repeated several times.

Cyst

Amoeba feeding and reproduction occurs throughout the summer. In autumn, when cold weather sets in, the amoeba stops eating, its body becomes rounded, a dense protective shell is released on its surface - a cyst is formed. The same thing happens when the pond where the amoeba lives dries up. In the state of a cyst, the amoeba endures unfavorable living conditions for it. When favorable conditions occur, the amoeba leaves the cyst shell. She releases pseudopods, begins to feed and multiply. Cysts carried by the wind contribute to the settlement of amoebas.