The bodies of living organisms can beone single cell, their group or a huge cluster of billions of such elementary structures. Most of the higher plants belong to the latter. The study of the cell - the main element of the structure and functions of living organisms - is engaged in cytology. This section of biology began to develop rapidly after the discovery of the electron microscope, the perfection of chromatography and other methods of biochemistry. Consider the main features, as well as the features by which the plant cell differs from the smallest structural units of the structure of bacteria, fungi and animals.
The theory of the tiny elements of the structure of everythingliving has passed the path of development, measured hundreds of years. The structure of the shell of plant cells was first seen in his microscope by the British scientist R. Hooke. General provisions of the cellular hypothesis were formulated by Schleiden and Schwann, before similar conclusions were made by other researchers.
The Englishman R.Hook examined the slice of oak plug in 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 bark of the tree consists of tiny cells called Hooke "cells." The walls of these chambers forming a pattern in the form of honeycombs, the scientist considered a living substance, and the cavity was recognized as a lifeless, auxiliary structure. Later it was proved that inside the cells of plants and animals contain a substance, without which their existence is impossible, and the activity of the whole organism.
An important discovery of R.Hooke developed in the works of other scientists who studied the structure of cells of animals and plants. Similar structural elements were observed by scientists on microscopic sections of multicellular fungi. It was found that the structural units of living organisms have the ability to divide. Based on the research, the representatives of the biological science of Germany M. Schleiden and T. Schwann formulated a hypothesis that later became a cellular theory.
Comparison of plant and animal cells withbacteria, algae and fungi allowed German researchers to come to the following conclusion: the "chambers" discovered by R. Hooke are elementary structural units, and the processes occurring in them are the basis of vital activity of the majority of organisms on the Earth. An important addition was introduced by R. Virchow in 1855, noting that cell division is the only way of their reproduction. The Schleiden-Schwann theory with refinements has become universally recognized in biology.
According to the theoretical statements of Schleiden andSchwanna, the organic world is one that proves a similar microscopic structure of animals and plants. In addition to these two kingdoms, cellular existence is characteristic of fungi, bacteria, and there are no viruses. The growth and development of living organisms is provided by the emergence of new cells in the process of dividing the already existing ones.
Multicellular organism is not just a clusterstructural elements. Small units of structure interact with each other, forming tissues and organs. Unicellular organisms live in isolation, which does not prevent them from creating colonies. The main signs of the cell are:
In the evolution of life, one of the most importantseparation of the nucleus from the cytoplasm by means of a protective membrane. Communication has survived, because separately these structures can not exist. At present, two super-kingdoms - nuclear-free and nuclear organisms - are singled out. The second group consists of plants, mushrooms and animals, which are studied by the relevant sections of science and biology in general. The cell of the plant has a nucleus, cytoplasm and organelles, which will be discussed below.
At the break of a ripe watermelon, apple or potatocan be seen with the naked eye structural "cells" filled with liquid. These are parenchyma cells of fruits, having a diameter of up to 1 mm. Bast fibers are elongated structures, the length of which considerably exceeds the width. For example, the plant cell, which is called cotton, reaches a length of 65 mm. The fibers of linseed and hemp have linear dimensions of 40-60 mm. Typical cells are much smaller than -20-50 microns. It is possible to consider such tiny structural elements only under a microscope. Features of the smallest units of the structure of the plant organism are manifested not only in differences in shape and size, but also in the functions performed in the tissue.
The nucleus and cytoplasm are closely interrelated andinteract with each other, which is confirmed by research scientists. These are the main parts of the eukaryotic cell, all the other elements of the structure depend on them. The nucleus serves to accumulate and transmit the genetic information necessary for protein synthesis.
Британский ученый Р.Brown in 1831 first noticed in the cell plants of the family of orchids a special body (nucleus). It was a nucleus surrounded by a semi-fluid cytoplasm. The name of this substance means in literal translation from the Greek "primary cell mass". It may be more liquid or viscous, but necessarily covered with a membrane. The outer shell of the cell consists mainly of cellulose, lignin, wax. One of the signs that distinguish plant and animal cells is the presence of this strong cellulose wall.
The inner part of the plant cell is filledgialoplazma with suspended in it the smallest granules. Closer to the shell, the so-called endoplasm passes into a more viscous exoplasm. It is these substances, which fill the cell of the plant, serve as a place for the flow of biochemical reactions and transport of compounds, the placement of organoids and inclusions.
Примерно 70–85 % цитоплазмы составляет вода, 10-20% are proteins, other chemical components - carbohydrates, lipids, mineral compounds. Plant cells have a cytoplasm in which among the final products of synthesis are bioregulators of functions and reserve substances (vitamins, enzymes, oils, starch).
Comparison of plant and animal cells shows,that they have a similar structure of the nucleus, which is in the cytoplasm and occupies up to 20% of its volume. The Englishman R. Brown, who for the first time considered this most important and constant component of all eukaryotes under a microscope, gave him the name from the Latin word nucleus. The appearance of nuclei usually correlates with the shape and size of cells, but sometimes differs from them. Mandatory elements of the structure - the membrane, karyolymph, nucleolus and chromatin.
In the membrane separating the nucleus from the cytoplasm,there are pores. Through them, substances come from the nucleus to the cytoplasm and back. Cariolymph is a liquid or viscous nuclear content with chromatin sites. The nucleolus contains ribonucleic acid (RNA), which penetrates into the ribosomes of the cytoplasm to participate in protein synthesis. Another nucleic acid, deoxyribonucleic (DNA), is also present in large quantities. DNA and RNA were first discovered in animal cells in 1869, later found in plants. The nucleus is a "control center" for intracellular processes, a place for storing information about hereditary traits of the whole organism.
The structure of cells of animals and plants hassignificant similarity. Indispensable are the inner tubules in the cytoplasm, filled with substances of different origin and composition. The granular variety of EPS differs from the agranular type by the presence of ribosomes on the membrane surface. The former is involved in the synthesis of proteins, the latter plays a role in the formation of carbohydrates and lipids. As the researchers established, the channels not only permeate the cytoplasm, they are associated with each organoid of a living cell. Therefore, the value of EPS is assessed very highly as a participant in metabolism, a system of communication with the environment.
The cell structure of plants or animals is difficultimagine without these small particles. Ribosomes are very small, you can only see them in the electron microscope. The Taurus is dominated by proteins and ribonucleic acid molecules, there is a small amount of calcium and magnesium ions. Almost all the amount of RNA cells is concentrated in the ribosomes, they provide protein synthesis, “collecting” proteins from amino acids. Then the proteins enter the EPS channels and are spread by the network throughout the cell, penetrate into the nucleus.
Эти органоиды клетки считают ее энергетическими Stations, they are visible under magnification in a conventional light microscope. The number of mitochondria varies in a very wide range, there may be a few or thousands of them. The structure of the organoid is not very complex, there are two membranes and a matrix inside. Mitochondria are composed of lipid protein, DNA and RNA, are responsible for the biosynthesis of ATP - adenosine triphosphate. For this substance, a plant or animal cell is characterized by the presence of three phosphates. Cleavage of each of them provides the energy necessary for all the vital processes in the cell itself and throughout the body. On the contrary, the addition of phosphoric acid residues makes it possible to store energy and transfer it in this form throughout the cell.
See the picture below.cell organelles and name those that you already know. Pay attention to the large bubble (vacuole) and green plastids (chloroplasts). We will talk about them delche.
A complex cellular organoid consists of granulesmembranes and vacuoles. The complex was opened in 1898 and received the name in honor of the Italian biologist. Features of plant cells are in 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, remove excess substances.
Only plant tissue cells contain organoids.green color. In addition, there are colorless, yellow and orange plastids. Their structure and functions reflect the type of plant nutrition, and they are able to change color due to chemical reactions. The main types of plastids:
The structure of the plant cell is associated with going to itchemical reactions of 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 due to chlorophyll, it is this substance that is able to capture the energy of a ray of light. The presence of green pigment explains the characteristic color of leaves, grassy stems, immature fruits. Chlorophyll in structure is similar to hemoglobin in the blood of animals and humans.
Red, yellow and orange color of variousplant organs due to the presence in the cells of chromoplastics. 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, along with it move along the inner shell of the plant cell. They are rich in enzymes, ions, and other biologically active compounds.
Most cells resemble a tiny pouch,filled with mucus, little bodies, granules and bubbles. Often there are different inclusions in the form of solid crystals of mineral substances, oil droplets, starch grains. The cells closely adjoin in the composition of plant tissues, life as a whole depends on the activities of these smallest units of the structure that make up the whole.
When multicellular structure existsspecialization, which is expressed in different physiological tasks and functions of microscopic structural elements. They are mainly determined by the location of the tissues in the leaves, root, stem or generative organs of the plant.
Let us single out the main elements of the performed comparison of the plant cell with the elementary units of the structure of other living organisms:
Among the algae, there are many solitary,free living cells. For example, such an independent organism is chlamydomonas. Although plants differ from animals in the presence of the cellulose cell wall, sex cells lack such a dense shell - this is yet another proof of the unity of the organic world.
