A cell is an elementary living system, the building block from which all living organisms are composed, only in multicellular organisms the cells differ in structure and function, but in unicellular organisms the cell itself is an entire organism.
Cells have all the properties of a living organism - metabolism, and therefore respiration, nutrition and excretion; production of energy necessary for life, reproduction with the transfer of hereditary information, etc.
All living matter on Earth is divided into two superkingdoms - prokaryotes (prenuclear) and eukaryotes (nuclear). Prokaryotes include bacteria and cyanobacteria. All other organisms are eukaryotes, i.e. have a core.
Let us consider in detail the structure of a plant cell.
Plant cells, like animal cells, consist of an outer membrane, cytoplasm (protoplasm) and a nucleus. The cytoplasm, in turn, consists of hyaloplasm, a jelly-like protein substance, and various organelles located in it.
Plants, fungi and bacteria, unlike animals and protozoa, have another membrane outside the cytoplasmic membrane - the so-called cell wall. It is rigid, durable, and performs protective, mechanical and transport functions. In plants, it consists of cellulose (fiber) and pectins. (in fungi, from chitin, and in bacteria, from polysaccharides). Over time, the cell wall becomes lignified and the cell dies.
In cereals and some other plants, minerals are deposited in the cell wall, making the plant tougher - this is a protection against being eaten by animals.
There are openings in the cell wall through which neighboring cells communicate with each other through processes called plasmodesmata.
Hyaloplasm is a thick solution of various inorganic and organic molecules in water. It moves inside the cell, carrying organelles with it. It can also allow certain substances to pass through and not others, participating in the metabolism both within the cell and between cells.
In addition, in the plant cell there are cavities bounded by a membrane and filled with viscous cell sap - vacuoles. Cellular sap is water with mineral salts and organic substances dissolved in it - glucose, fructose, pectins, etc., as well as metabolic products. Sometimes the cell sap is colored and gives color to the plant, for example, in red cabbage. In old cells, the vacuole can occupy almost the entire volume of the cell. Vacuoles serve as a storage area for water reserves in the cell and impart turgor (density) to plant tissues.
Cytoskeleton. The cytoplasm of eukaryotic cells is penetrated by a three-dimensional network of protein threads that form the so-called cytoskeleton. The cytoskeleton performs three main functions:
- Serves as a mechanical framework that gives the cell its shape, and also connects the membrane with organelles
- Works as a motor during movement or operation of a cell (in animals - the work of muscles, in plants - the movement of leaves, the opening of petals, etc.)
- Serves as “rails” for the movement of organelles, such as mitochondria or plastids, within the cell
Mitochondria
Mitochondria are the energy stations of the cell. They produce the energy necessary for all life processes in the cell. Absorbing organic substances from the cytoplasm, mitochondria break them down with the participation of oxygen (in other words, “burn”), and synthesize ATP molecules from them - the main source of energy in the cell. This also produces water and carbon dioxide. Thus, mitochondria are the main consumers of oxygen in the cell, and are the first to suffer when there is a lack of oxygen. Mitochondria consist of two membranes, a smooth outer membrane and a folded inner one. The folds of the inner membrane form septa - cristae.
Plastids
Plastids are organelles consisting of membranes and containing special pigments. Plastids are found only in plants.
There are three types of plastids: chloroplasts, chromoplasts and leucoplasts.
Chloroplasts- contain the green pigment chlorophyll, they are present in the leaves and other green parts of the plant. Chloroplasts are involved in photosynthesis - the formation of organic substances from water and carbon dioxide, using the energy of sunlight.
Chromoplasts are plastids containing another pigment - red or yellow. Chromoplasts give color to flowers and autumn leaves. They create all the diversity and beauty of the plant world.
And finally, leucoplasts are colorless plastids; they are found in the cells of bulbs, roots, stems and other uncolored parts of plants. But some organic substances accumulate in them.
Under certain conditions, different types of plastids can transform into each other.
Core
The nucleus is the repository of hereditary information - DNA, as well as the main regulator of protein synthesis. Nucleoli can be seen in the nucleus; they disappear when the cell begins to divide. Ribosomes, organelles responsible for protein synthesis, are formed in the nucleoli. DNA is found in the nucleus in the form of chromosomes.
Endoplasmic reticulum
The endoplasmic reticulum is a system of membranes and cisterns that communicate with the nucleus, passing into its membrane. This is caused by the general functions of these organelles - the synthesis of protein and other substances. There are smooth and rough endoplasmic reticulum. Ribosomes are located on the membranes of the rough endoplasmic reticulum. Its function is protein synthesis. The smooth endoplasmic reticulum is involved in the synthesis of lipids, participates in carbohydrate metabolism, etc.
Golgi apparatus - This is another membrane organelle of the cell. The Golgi apparatus looks like a stack of cisterns from which vesicles—secretory granules—come off. The Golgi apparatus is connected to the endoplasmic reticulum, and is involved in the secretion and transport of proteins, enzymes and everything that was synthesized in it. The resulting vesicles with secretions - lysosomes - can both move around the cell and bring the secretion out into the intercellular space.
Ribosomes - small but very important organelles responsible for protein synthesis. They are found in the cell both in a free state and attached to the membranes of the rough endoplasmic reticulum.
Cell center (or centrosome)- Not all plants have it. This is a non-membrane organelle that is involved in the cell cycle - cell division, as well as in the formation of flagella and cilia in some plants.
So, we have examined the main organelles of a plant cell, and now let’s summarize what they are responsible for:
Organelle |
Function in cell |
| Core | Storage and transmission of hereditary information, protein synthesis |
| Mitochondria | Generating energy for the cell and storing it in the form of ATP |
| Plastids | Chloroplasts - Photosynthesis - the formation of organic substances from carbon dioxide and water in the light Chromoplasts - Give color, attractive to insects and animals Leukoplasts - store nutrients |
| Endoplasmic reticulum | Synthesis of protein, fats and other substances |
| Golgi apparatus | Transport and secretion of substances |
| Ribosomes | Protein synthesis |
| Cell center | Participates in cell division, formation of flagella and cilia |
| Vacuole | Stores water, minerals and organic substances |
The bodies of living organisms can be a single cell, a group of them, or a huge cluster of billions of such elementary structures. The latter include the majority. Cytology deals with the study of the cell - the main element of the structure and functions of living organisms. This section of biology began to develop rapidly after the discovery of the electron microscope, the improvement of chromatography and other methods of biochemistry. Let us consider the main characteristics, as well as the features by which a plant cell differs from the smallest structural units of bacteria, fungi and animals.
Discovery of the cell by R. Hooke
The theory about the tiny elements of the structure of all living things has gone through a development path measured in hundreds of years. The structure of the plant cell membrane was first seen by the British scientist R. Hooke through his microscope. The general provisions of the cell hypothesis were formulated by Schleiden and Schwann; before that, other researchers made similar conclusions.
The Englishman R. Hooke examined a section of oak cork through a microscope and presented the results at a meeting of the Royal Society in London on April 13, 1663 (according to other sources, the event occurred in 1665). It turned out that the tree bark consists of tiny cells, called “cells” by Hooke. The scientist considered the walls of these chambers, forming a pattern in the form of a honeycomb, to be a living substance, and recognized the cavity as a lifeless, auxiliary structure. Later it was proven that inside the cells of plants and animals they contain a substance, without which their existence, and indeed the activity of the entire organism, is impossible.
Cell theory
The important discovery of R. Hooke was developed in the works of other scientists who also studied plants. Scientists observed similar structural elements in microscopic sections of multicellular fungi. It was found that the structural units of living organisms have the ability to divide. Based on research, representatives of German biological science M. Schleiden and T. Schwann formulated a hypothesis, which later became the cell theory.
With bacteria, algae and fungi, German researchers came to the following conclusion: the “chambers” discovered by R. Hooke are elementary structural units, and the processes occurring in them underlie the life activity of most organisms on Earth. An important addition was made by R. Virchow in 1855, noting that cell division is the only way for their reproduction. The Schleiden-Schwann theory with refinements has become generally accepted in biology.
A cell is the smallest element of the structure and life of plants
According to theoretical principles, the organic world is one, which proves the similar microscopic structure of animals and plants. In addition to these two kingdoms, cellular existence is characteristic of fungi and bacteria, but is absent in viruses. The growth and development of living organisms is ensured by the emergence of new cells during the division of existing ones.
A multicellular organism is not just a collection of structural elements. Small structural units interact with each other to form tissues and organs. Single-celled organisms live in isolation, which does not prevent them from creating colonies. The main characteristics of a cell:
- ability for independent existence;
- own metabolism;
- self-reproduction;
- development.
In the evolution of life, one of the most important stages was the separation of the nucleus from the cytoplasm using a protective membrane. The connection has been preserved, because these structures cannot exist separately. Currently, two superkingdoms are distinguished: non-nuclear and nuclear organisms. The second group consists of plants, fungi and animals, the study of which is carried out by the corresponding branches of science and biology in general. A plant cell has a nucleus, cytoplasm and organelles, which will be discussed below.
Diversity of plant cells
On the break of a ripe watermelon, apple or potato, you can see structural “cells” filled with liquid with the naked eye. These are fetal parenchyma cells with a diameter of up to 1 mm. Bast fibers are elongated structures, the length of which significantly exceeds the width. For example, the cell of a plant called cotton reaches a length of 65 mm. The bast fibers of flax and hemp have linear dimensions of 40-60 mm. Typical cells are much smaller -20-50 microns. Such tiny structural elements can only be seen under a microscope. The characteristics of the smallest structural units of a plant organism are manifested not only in differences in shape and size, but also in the functions performed within the tissue composition.
Plant cell: main structural features
The nucleus and cytoplasm are closely interconnected and interact with each other, which is confirmed by scientific research. These are the main parts; all other elements of the structure depend on them. The nucleus serves to accumulate and transmit genetic information necessary for protein synthesis.
The British scientist R. Brown in 1831 first noticed a special body (nucleus) in the cell of a plant of the orchid family. It was a nucleus surrounded by semi-liquid cytoplasm. The name of this substance means, literally translated from Greek, “primary cell mass.” It may be more liquid or viscous, but it is always covered with a membrane. The outer cell membrane consists mainly of cellulose, lignin, and wax. One of the characteristics that distinguishes plant and animal cells is the presence of this strong cellulose wall.
The structure of the cytoplasm
The internal part is filled with hyaloplasm with tiny granules suspended in it. Closer to the shell, the so-called endoplasm transforms into a more viscous exoplasm. It is these substances that fill the plant cell that serve as the site for biochemical reactions and transport of compounds, placement of organelles and inclusions.
Approximately 70-85% of the cytoplasm is water, 10-20% is proteins, other chemical components are carbohydrates, lipids, mineral compounds. Plant cells have a cytoplasm in which, among the final products of synthesis, there are bioregulators of functions and storage substances (vitamins, enzymes, oils, starch).
Core
A comparison of plant and animal cells shows that they have a similar structure of the nucleus, located in the cytoplasm and occupying up to 20% of its volume. The Englishman R. Brown, who first examined this important and constant component of all eukaryotes under a microscope, gave it its name from the Latin word nucleus. The appearance of the nuclei usually correlates with the shape and size of the cells, but sometimes differs from them. Mandatory structural elements are membrane, karyolymph, nucleolus and chromatin.
The membrane separating the nucleus from the cytoplasm has pores. Through them, substances move from the nucleus to the cytoplasm and back. Karyolymph is a liquid or viscous nuclear content with patches of chromatin. The nucleolus contains ribonucleic acid (RNA), which penetrates the ribosomes of the cytoplasm to participate in protein synthesis. Another nucleic acid, deoxyribonucleic acid (DNA), is also present in large quantities. DNA and RNA were first discovered in animal cells in 1869 and subsequently found in plants. The nucleus is the “control center” of intracellular processes, the storage place for information about the hereditary characteristics of the whole organism.
Endoplasmic reticulum (ER)
The structure of animal and plant cells is significantly similar. Internal tubules filled with substances of different origin and composition are necessarily present in the cytoplasm. The granular type of EPS differs from the agranular type by the presence of ribosomes on the surface of the membranes. The first is involved in the synthesis of proteins, the second plays a role in the formation of carbohydrates and lipids. As the researchers have established, the channels not only penetrate the cytoplasm, they are connected to every organelle of a living cell. Therefore, the importance of EPS is assessed very highly as a participant in metabolism and a system of communication with the environment.
Ribosomes
The structure of a plant or animal cell is difficult to imagine without these small particles. Ribosomes are very small and can only be seen with an electron microscope. The composition of the bodies is dominated by proteins and molecules of ribonucleic acids; there are small amounts of calcium and magnesium ions. Almost the entire amount of RNA in a cell is concentrated in ribosomes; they provide protein synthesis, “assembling” proteins from amino acids. Then the proteins enter the ER channels and are distributed throughout the cell by the network and penetrate into the nucleus.
Mitochondria
These organelles of the cell are considered its energy stations and are visible under magnification with a regular light microscope. The number of mitochondria varies widely; there can be a few or thousands of them. The structure of the organoid is not very complicated; there are two membranes and a matrix inside. Mitochondria consist of protein lipids, DNA and RNA, and are responsible for the biosynthesis of ATP - adenosine triphosphoric acid. This substance in plant or animal cells is characterized by the presence of three phosphates. The cleavage of each of them provides the energy necessary for all vital processes in the cell itself and in the entire body. On the contrary, the addition of residues makes it possible to store energy and transport it in this form throughout the cell.
Look at the cell organelles in the figure below and name those that you already know. Note the large vesicle (vacuole) and green plastids (chloroplasts). We will talk about them in more detail.
Golgi complex
The complex cellular organelle consists of granules, membranes and vacuoles. The complex was opened in 1898 and was named after the Italian biologist. Features of plant cells include the uniform distribution of Golgi particles throughout the cytoplasm. Scientists believe that the complex is necessary to regulate the content of water and waste products, and remove excess substances.
Plastids
Only plant tissue cells contain green organelles. In addition, there are colorless, yellow and orange plastids. Their structure and functions reflect the type of plant nutrition, and they are capable of changing color due to chemical reactions. Main types of plastids:
- orange and yellow chromoplasts formed by carotene and xanthophyll;
- chloroplasts containing grains of chlorophyll, a green pigment;
- Leucoplasts are colorless plastids.
The structure of a plant cell is associated with the chemical reactions occurring in it, the synthesis of organic matter from carbon dioxide and water using light energy. The name of this amazing and very complex process is photosynthesis. Reactions are carried out thanks to chlorophyll; it is this substance that is able to capture the energy of a light beam. The presence of green pigment explains the characteristic color of leaves, herbaceous stems, and unripe fruits. Chlorophyll is similar in structure to hemoglobin in the blood of animals and humans.
The red, yellow and orange color of various plant organs is due to the presence of chromoplasts in the cells. They are based on a large group of carotenoids that play an important role in metabolism. Leukoplasts are responsible for the synthesis and accumulation of starch. Plastids grow and multiply in the cytoplasm, moving along with it along the inner membrane of the plant cell. They are rich in enzymes, ions, and other biologically active compounds.
Differences in the microscopic structure of the main groups of living organisms
Most cells resemble a tiny sac filled with mucus, bodies, granules and vesicles. Various inclusions are often present in the form of solid crystals of mineral substances, drops of oils, and starch grains. Cells are closely connected in the composition of plant tissues; life as a whole depends on the activity of these smallest structural units that form the whole.
With a multicellular structure, there is specialization, which is expressed in different physiological tasks and functions of microscopic structural elements. They are determined mainly by the location of tissues in the leaves, roots, stems or generative organs of the plant.
Let us highlight the main elements of the comparison of a plant cell with the elementary structural units of other living organisms:
- The dense shell, characteristic only of plants, is formed by fiber (cellulose). In fungi, the membrane consists of durable chitin (a special protein).
- Plant and fungal cells differ in color due to the presence or absence of plastids. Bodies such as chloroplasts, chromoplasts and leucoplasts are present only in the plant cytoplasm.
- There is an organelle that distinguishes animals - the centriole (cellular center).
- Only the plant cell contains a large central vacuole filled with liquid contents. Usually this cell sap is colored with pigments in different colors.
- The main reserve compound of the plant organism is starch. Fungi and animals accumulate glycogen in their cells.
Among algae, many single, free-living cells are known. For example, such an independent organism is Chlamydomonas. Although plants differ from animals in the presence of a cellulose cell wall, sex cells lack such a dense membrane - this is another proof of the unity of the organic world.
The cells of various organs and tissues of higher plants differ from each other in shape, size, color, and internal structure. However, plant cells are characterized by a number of features that distinguish them from cells of other groups of organisms.
If you examine a sample of onion skin under a light microscope, you can easily see cells that fit tightly together. Although the membranes of these cells are quite strong, they are at the same time transparent. Cell membrane has pores. Under a microscope, they appear as thinner sections of the cell membrane.
Under the cell membrane is cytoplasmic membrane.
Under the membrane is cytoplasm, which is a viscous liquid, usually colorless. The cytoplasm in living cells is constantly moving, many chemical reactions occur in it. The movement of the cytoplasm can be judged by the movement of the organelles and inclusions contained in it, which can be visible under a light microscope. Unfavorable environmental conditions (for example, too high or low temperature) can lead to destruction of the cytoplasm and, as a result, cell death.
The cytoplasms of neighboring cells are usually connected to each other by cytoplasmic filaments passing through the cell membranes.
Located in the cytoplasm cell nucleus. It is a denser body and occupies a small part of the cell. Inside the core is nucleolus And chromosomes. You can see all the structural features of the plant cell nucleus only with the help of an electron microscope.
The nucleus plays an important role in cell division. Before division, it becomes larger, and the chromosomes curl and become clearly visible under a microscope. Chromosomes contain hereditary information about an organism. During division, chromosomes are doubled, and each daughter cell receives the same set of chromosomes that was in the mother cell before the division process began. Thanks to cell division in educational tissues and their subsequent growth, the growth of the entire plant occurs.
The bulk of most plant cells is occupied by vacuoles. In adult and old cells, vacuoles merge into one large central vacuole. The vacuoles contain cell sap, which is a solution of various organic and inorganic compounds. There are a lot of sugars and pigments in the cell sap. Various pigments give cells bluish, reddish and other colors.
When the central vacuole becomes very large and occupies almost the entire volume of the plant cell, the cytoplasm and the organelles contained in it are pushed towards the membrane.
A lot of cell sap is contained in the tissues of juicy fruits and other soft and bulky parts of plants. What we call the juices of various fruits is precisely the cell juice of cell vacuoles.
A feature of the structure of a plant cell is the presence in it plastid. There are no such organelles in animal cells. Plastids can even be seen with a light microscope.
There are three types of plastids: chloroplasts, leucoplasts and chromoplasts. Chloroplasts have a green color due to the presence of pigment in them chlorophyll. Thanks to it, the process of photosynthesis can occur in plants, as a result of which organic substances are synthesized from inorganic substances.
Leukoplasts They are colorless plastids. They usually contain a supply of nutrients.
Chromoplasts may have different colors depending on what pigments they contain. Thanks to chromoplasts, tree foliage turns different colors in autumn.
In plant tissues, cells are connected to each other by an intercellular substance. However, in some places there may be no intercellular substance. In this case, intercellular spaces containing air are formed. This promotes gas exchange between the cell and the environment.
Cell– the smallest structural and biological unit of living matter. All vital processes are inherent in it: nutrition, breathing, growth, irritability, reproduction, heredity. It appeared at a certain stage of evolution as a result of the improvement of living matter. The number of cells in organisms varies from one to several billion. If there is only one cell, then it acts as a complete organism and performs all its functions.
The term “cell” was first proposed by Robert Hooke in 1665. Significant contributions to the study of plant cells were made by scientists M. Malpighi (Italian), N. Grew (English), M. Schleiden and T. Schwann (German). It was Schleiden and Schwann, based on their own research and the research of other scientists, who showed that the cellular structure is inherent in all living organisms (cellular theory, 1839).
Let us consider the general structure of a plant cell.
The outside of the plant cell is covered cell membrane (wall). It is formed from substances produced by the cytoplasm, which are deposited outside it, creating a shell (pectin, hemicellulose and cellulose). This is how the primary shell is formed. It is elastic, does not interfere with cell growth, creates strength and gives a certain shape, protects the contents from mechanical damage. Many cells also develop a secondary membrane. It is formed under the primary shell and consists of cellulose. Cells with a secondary membrane are stronger and can perform a mechanical function. There are unthickened places in the shell - pores. Thin strands of cytoplasm pass through them, through which the exchange of substances between neighboring cells occurs.
Cell wall modifications:
Lignification - the shell is impregnated with lignin, which acts as cement, imparts hardness and strength (typical of mechanical tissue cells and wood);
Suberization - the shell is impregnated with suberin (a fat-like substance), the access of water and gases is stopped. The contents of the cell die, it fills with air and performs the function of thermal insulation (integumentary tissue of cork oak);
Cutinization - epidermal cells are impregnated with cutin and wax. Functions: reduction of transpiration, reflection of light, protection from UV rays and infection by microorganisms;
Mineralization - impregnation of the shell with mineral salts (for example, calcium). This gives the cells rigidity and hardness; plants are not eaten by animals (horsetails, sedges);
Slime - swelling of pectin substances in the shell (seed skin cells during germination, cell membranes during wounding).
The entire contents of the cell are divided into 2 parts:
Protoplast (living contents);
Protoplast derivatives (non-living contents).
Protoplast It is a cytoplasm with organelles enclosed in it (nucleus, plastids, mitochondria, Golgi apparatus, spherosomes, ribosomes, endoplasmic reticulum, lysosomes). The number of organelles and their composition depend on the function, specific life activity of the cell and its age.
Under the cell wall is cytoplasm. Its outer layer is plasmalemma– is a membrane that allows selective penetration of substances into and out of the cell. It has a three-layer structure typical for membranes. The outer and inner layers consist of one row of protein molecules and two rows of lipids between them. The membrane has very thin through holes through which some substances can pass and others are retained (it is semi-permeable).
A continuation of the plasmalemma membrane is endoplasmic reticulum (reticulum), which is a network of channels and cavities. The ER is a conveyor belt for the synthesis and movement of substances throughout the cell. Starting from the plasmalemma, it approaches various organelles and the outer shell of the nucleus. Connected to EPS channels Golgi apparatus. It performs the function of accumulating and gradually removing synthesized substances from the cell.
The energy stations of cells are mitochondria. They consist of two membranes. They carry out cell respiration, resulting in the release of energy. It binds, turning into the energy of the phosphate bond of ATP. The number of mitochondria depends on the activity of the cell, its age and physiological state.
Lysosomes- small round bodies with a very strong membrane. The lysosome matrix contains highly active enzymes that digest food substances and destroy dead parts of the cell.
Spherosomes– similar in shape and size to lysosomes, there is a protein matrix inside. The main function is the accumulation of oils.
Present in the cytoplasm of cells microtubules, involved in the formation of the cell membrane of dividing cells.
Ribosomes– small bodies of a spherical or slightly flattened shape, the structure lacks a membrane system. The main function is protein synthesis.
Plastids- organelles unique to plant cells. These are large double-membrane organelles, clearly visible under a light microscope. There are three types based on color and functions:
1). Chloroplasts: have the shape of a biconvex lens. On the outside, they are covered with a shell consisting of two membranes. The outer membrane is smooth, the inner one has plate-shaped outgrowths. These plates are called lamellae. They lie on top of each other in regular stacks, reminiscent of columns of coins, and are called grana. Photosynthetic pigments are localized in the internal membranes (in higher plants - chlorophyll a and b, in algae chlorophyll c, d, e may appear). Chlorophyll gives the green color to chloroplasts. There are other pigments in chloroplasts: red-orange - carotene and yellow - xanthophyll, but they are not visible under the predominant mass of chlorophyll.
2). Chromoplasts: larger than chloroplasts. These are red-orange and yellow plastids. Coloring pigments of the carotenoid group (there are more than 50 of them, but the most common are carotene and xanthophyll). They give color to flower petals, fruits, and roots.
3). Leukoplasts: have no pigment and are colorless. They are formed in organs hidden from sunlight. Their function is the synthesis and accumulation of reserve nutrients.
The most important organelle of any eukaryotic cell is core. It contains the genetic information of the cell, controls its vital activity, influencing protein synthesis. The nucleus is separated from the cytoplasm by a double-membrane membrane. The shell is permeated with pores, through which communication with the EPS channels is carried out and, thereby, contact of the nucleus with the cytoplasm is ensured. The core consists of nuclear juice, representing a mixture of enzyme proteins, nucleotides and amino acids, chromosomes, built from DNA molecules and containing genetic material, and nucleolus which carries out RNA synthesis and ribosome assembly.
A plant cell is characterized by the presence vacuoles. They often occupy almost the entire volume of the cell. Young cells have several of them. As cells develop, they grow and merge into one. Contents – cell sap– an aqueous solution of many substances: sugars, amino acids, pigments, vitamins, etc. All these substances are products of cell vital activity.
The membrane separating the cytoplasm from the vacuoles is called the inner membrane or tonoplast. Its function is transport.
Thus, a plant cell has all the characteristics of an ordinary eukaryotic cell.
Differences in the structure of plant and animal cells:
The plant cell has a well-developed cell wall;
A plant cell contains plastids (on this basis, most plants are classified as autotrophs);
Vacuoles are always present in a plant cell: several small ones in young cells, or one large one in adults.
Many key differences between plants and animals originate in structural differences at the cellular level. Some have some parts that others have, and vice versa. Before we find the main difference between an animal cell and a plant cell (table later in the article), let's find out what they have in common, and then explore what makes them different.
Animals and plants
Are you slouched in your chair reading this article? Try to sit up straight, extend your arms to the sky and stretch. Feeling good, right? Whether you like it or not, you are an animal. Your cells are soft blobs of cytoplasm, but you can use your muscles and bones to stand and move around. Hetorotrophs, like all animals, must receive nutrition from other sources. If you feel hungry or thirsty, you just need to get up and walk to the refrigerator.
Now think about plants. Imagine a tall oak tree or tiny blades of grass. They stand upright without muscles or bones, but they cannot afford to walk anywhere to get food and drink. Plants, autotrophs, create their own products using the energy of the sun. The difference between an animal cell and a plant cell in Table No. 1 (see below) is obvious, but there are also many similarities.
general characteristics
Plant and animal cells are eukaryotic, and this is already a great similarity. They have a membrane-bound core that contains genetic material (DNA). A semipermeable plasma membrane surrounds both types of cells. Their cytoplasm contains many of the same parts and organelles, including ribosomes, Golgi complexes, endoplasmic reticulum, mitochondria and peroxisomes, among others. While plant and animal cells are eukaryotic and have many similarities, they also differ in several ways.
Features of plant cells
Now let's look at the features How can most of them stand upright? This ability is due to the cell wall, which surrounds the membranes of all plant cells, provides support and rigidity, and often gives them a rectangular or even hexagonal appearance when observed under a microscope. All these structural units have a rigid, regular shape and contain many chloroplasts. The walls can be several micrometers thick. Their composition varies among plant groups, but they typically consist of fibers of the carbohydrate cellulose embedded in a matrix of proteins and other carbohydrates.
Cell walls help maintain strength. The pressure created by water absorption contributes to their rigidity and allows for vertical growth. Plants are unable to move from place to place, so they need to make their own food. An organelle called a chloroplast is responsible for photosynthesis. Plant cells can contain several such organelles, sometimes hundreds.
Chloroplasts are surrounded by a double membrane and contain stacks of membrane-bound disks in which sunlight is absorbed by special pigments and this energy is used to power the plant. One of the most famous structures is the large central vacuole. occupies most of the volume and is surrounded by a membrane called tonoplast. It stores water, as well as potassium and chloride ions. As the cell grows, the vacuole absorbs water and helps elongate the cells.
Differences between an animal cell and a plant cell (Table No. 1)
Plant and animal structural units have some differences and similarities. For example, the former do not have a cell wall and chloroplasts, they are round and irregular in shape, while plants have a fixed rectangular shape. Both are eukaryotic, so they have a number of common features, such as the presence of a membrane and organelles (nucleus, mitochondria and endoplasmic reticulum). So, let's look at the similarities and differences between plant and animal cells in Table No. 1:
| animal cell | plant cell | |
| Cell wall | absent | present (formed from cellulose) |
| Form | round (irregular) | rectangular (fixed) |
| Vacuole | one or more small ones (much smaller than in plant cells) | One large central vacuole occupies up to 90% of the cell volume |
| Centrioles | present in all animal cells | present in lower plant forms |
| Chloroplasts | No | Plant cells have chloroplasts because they create their own food |
| Cytoplasm | There is | There is |
| Ribosomes | present | present |
| Mitochondria | available | available |
| Plastids | none | present |
| Endoplasmic reticulum (smooth and rough) | There is | There is |
| Golgi apparatus | available | available |
| Plasma membrane | present | present |
| Flagella | can be found in some cells | |
| Lysosomes | present in the cytoplasm | usually not visible |
| Cores | present | present |
| Cilia | are present in large quantities | plant cells do not contain cilia |
Animals vs plants
What conclusion can be drawn from the table “Difference between an animal cell and a plant cell”? Both are eukaryotic. They have true nuclei where the DNA is located and are separated from other structures by a nuclear membrane. Both types have similar reproductive processes, including mitosis and meiosis. Animals and plants need energy; they must grow and maintain normal energy through the process of respiration.
Both have structures known as organelles that are specialized to perform functions necessary for normal functioning. The presented differences between an animal cell and a plant cell in Table No. 1 are supplemented by some common features. It turns out they have a lot in common. Both have some of the same components, including the nucleus, Golgi complex, endoplasmic reticulum, ribosomes, mitochondria, and so on.
What is the difference between a plant cell and an animal cell?
Table No. 1 presents the similarities and differences quite briefly. Let's consider these and other points in more detail.
- Size. Animal cells are usually smaller than plant cells. The former range from 10 to 30 micrometers in length, while plant cells have a length range of 10 to 100 micrometers.
- Form. Animal cells come in a variety of sizes and are typically round or irregular in shape. Plants are more similar in size and tend to be rectangular or cubic in shape.
- Energy storage. Animal cells store energy in the form of complex carbohydrates (glycogen). Plants store energy in the form of starch.
- Differentiation. In animal cells, only stem cells are capable of transitioning into others. Most types of plant cells are not capable of differentiation.
- Height. Animal cells increase in size due to the number of cells. Plants absorb more water in the central vacuole.
- Centrioles. Animal cells contain cylindrical structures that organize the assembly of microtubules during cell division. Plants, as a rule, do not contain centrioles.
- Cilia. They are found in animal cells but are not common in plant cells.
- Lysosomes. These organelles contain enzymes that digest macromolecules. Plant cells rarely contain the function of a vacuole.
- Plastids. Animal cells do not have plastids. Plant cells contain plastids, such as chloroplasts, which are essential for photosynthesis.
- Vacuole. Animal cells can have many small vacuoles. Plant cells have a large central vacuole, which can occupy up to 90% of the cell volume.
Structurally, plant and animal cells are very similar, containing membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes and peroxisomes. Both also contain similar membranes, cytosol, and cytoskeletal elements. The functions of these organelles are also very similar. However, the small difference between a plant cell and an animal cell (Table No. 1) that exists between them is very significant and reflects the difference in the functions of each cell.
So, we found out what their similarities and differences are. The common features are the structural plan, chemical processes and composition, division and genetic code.
At the same time, these smallest units are fundamentally different in the way they feed.
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