The bodies of living organisms may be one single cell, their group or cluster of huge, numbering billions of elementary structures.The latter includes most of the higher plants.The study of cells - the main element of the structure and function of living organisms - is engaged in cytology.This section of biology began to develop rapidly after the discovery of the electron microscope, improved chromatography and other methods of biochemistry.Consider the main features and characteristics of plant cell that differs from the smallest structural units of the structure of bacteria, fungi and animals.
Opening cells R. Hooke
theory of tiny building blocks of all life has evolved, measured in hundreds of years.The structure of the cell wall of plants for the first time saw his microscope British scientist Robert Hooke.General The cell hypothesis formulated Schleiden and Schwann, before making similar findings by other researchers.
Englishman Robert Hooke examined under a microscope section of cork oak, and presented the results at a meeting of the Royal Society in London on April 13, 1663 (according to other sources, the event took place in 1665).It was found that the bark is made up of tiny cells called Hooke "cells."The walls of these chambers, forming a pattern in the form of honeycomb, the scientist considered living matter, and the cavity found lifeless, support structure.Later it was proved that the inside of the plant cells and animals containing substance, without which their existence, and the activity of the whole organism.
cell theory
important discovery Robert Hooke was developed in the works of other scholars who have studied the structure of the cells of animals and plants.Similar elements of the structure observed by scientists at the microscopic sections of multicellular fungi.It was found that the structural unit of living organisms have the ability to divide.Based on studies of biological science German representatives M. Schleiden and T. Schwann formulated the hypothesis that became cell theory.
comparing plant and animal cells with bacteria, algae and fungi has allowed German researchers to come to the following conclusion: R. Hooke discovered "camera" - a basic structural units, and reaching them in the processes of life are the basis of most organisms on Earth.An important addition made Virchow in 1855, noting that cell division - the only way to their breeding grounds.The theory of Schleiden-Schwann Clarifications became recognized in biology.
Cell - the smallest element of the structure and activity of plants
According to the theoretical provisions of Schleiden and Schwann, the organic world is one that shows a similar microscopic structure of plants and animals.Apart from these two realms, the existence of a cell characteristic of fungi, bacteria and viruses have not.The growth and development of living organisms is provided by the emergence of new cells in the process of dividing the existing ones.
multicellular organisms - not just the accumulation of structural elements.Small building unit interact to form tissues and organs.Single-celled organisms live in isolation, which does not prevent them to create a colony.The main features of the cells:
- capacity for independent existence;
- own metabolism;
- self-reproduction;
- development.
evolution of life in one of the most important steps was the separation of the nucleus from the cytoplasm by means of a protective membrane.Communication is preserved, because these structures alone can not exist.Now it allocates two superkingdom - non-nuclear and nuclear organisms.The second group consists of plants, fungi and animals, which are engaged in the study of the relevant sections of science and biology in general.Plant cells have nucleus, cytoplasm and organelles, which will be mentioned below.
A variety of plant cells
At the turn of ripe watermelon, apples or potatoes can be seen with the naked eye structure "cell", filled with liquid.This parenchyma cells fruit having a diameter of 1 mm.Bast fibers - elongated structure, the length of which is significantly greater than the width.For example, a plant cell, which is called the cotton reaches a length of 65 mm.Bast fibers of flax and hemp have linear dimensions of 40-60 mm.Typical cells much less -20-50 microns.Consider these tiny structural elements may be only under a microscope.Features of the smallest units of the structure of the plant organism are manifested not only in the differences in shape and size, but also in the functions performed as part of the tissues.
plant cells: the main features of the structure
nucleus and cytoplasm are closely interrelated and interact with each other, which is confirmed by research scientists.These are the main parts of eukaryotic cells, which are dependent on the other elements of the structure.The kernel used for accumulation and transfer of genetic information required for protein synthesis.
British scientist Robert Brown in 1831 for the first time observed in the plant cell orchid family special body (Nucleus).This was a core surrounded by semi cytoplasm.The name of the substance is in a literal translation from the Greek "primary cell mass."It may be a liquid or viscous, but always covered with a membrane.Outer sheath cells consists mostly of cellulose, lignin, wax.One of the characteristics that distinguish the cells of plants and animals, - the presence of the solid cellulose wall.
structure cytoplasm
inner part of the plant cell is filled with hyaloplasm suspended in it tiny granules.Closer to the so-called shell endoplasma becomes more viscous ekzoplazmu.These are substances that are filled with plant cell, providing a forum to biochemical reactions and transport connections, placement of organelles and inclusions.
Approximately 70-85% of the cytoplasm of water, 10-20% are proteins, and other chemical components - carbohydrates, lipids, mineral compounds.Plant cells have cytoplasm, which, among the final products of synthesis are present bioregulatory functions and replacement substances (vitamins, enzymes, oils, starch).
kernel
comparing cells of plants and animals shows that they have a similar structure of the nucleus in the cytoplasm, and takes up 20% of its volume.The Englishman R. Brown, who considered under the microscope for the first time this important and permanent component of all eukaryotes, gave him the name from the Latin word nucleus.Appearance nuclei usually correlates to the shape and size of the cells, but sometimes different.Required elements of the structure - membrane karyolymph, the nucleolus and chromatin.
In the membrane separating the nucleus from the cytoplasm, there are pores.Through these substances come from the nucleus to the cytoplasm and back.Karyolymph is a liquid or viscous contents from the nuclear chromatin sites.The nucleolus contains ribonucleic acid (RNA), enters the ribosome cytoplasm to participate in protein synthesis.Other nucleic acid - deoxyribonucleic (DNA) - is also present in large quantities.DNA and RNA were first observed in animal cells in 1869, subsequently found in plants.The kernel - a "control center" of intracellular processes, storage of information on hereditary characteristics of the whole organism.
endoplasmic reticulum (EPS)
structure of animal and plant cells has significant similarities.Always present in the cytoplasm of the inner canals filled with different origin and composition of the substance.Granular variety EPS differs from the presence of the smooth type ribosomes on the membrane surface.The first involved in protein synthesis, plays a second role in the formation of carbohydrates and lipids.As established investigators, the channels are not only penetrate the cytoplasm, they are connected with each organelles of living cells.Therefore, the value of EPS is highly appreciated as a participant in metabolism, the communication system with the environment.
Ribosomes
structure cells of plants or animals is difficult to imagine without these small particles.Ribosomes are very small, they can be seen only through an electron microscope.As part of the cells is dominated by proteins and molecules of ribonucleic acid, has a small amount of calcium and magnesium ions.Almost all the amount of RNA in the cells ribosomes are concentrated, they provide protein synthesis, "Grouping" proteins from amino acids.The proteins are then received into the channels and spread EPS network throughout the cell into the nucleus.
Mitochondria
These cell organelles consider her power plants, they can be seen with the increase in ordinary light microscope.The number of mitochondria varies within very wide limits, they may be as many units or thousands.Organelle structure does not differ very complex, there are two membranes and matrix inside.The mitochondria consist of lipid protein, DNA and RNA, are responsible for the biosynthesis of ATP - adenosine triphosphate.For this purpose substances of animal or plant cells 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.Conversely, addition of phosphoric acid residues allows to store and to transfer energy in this way throughout the cell.
Consider the following figure organelles cells and name the ones you already know.Note the large bubble (vacuole) and green plastids (chloroplasts).We will discuss them delshe.
Golgi complex
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 are as evenly distributing the particles throughout the cytoplasm Golgi.Scientists believe that the complex is required for controlling the content of water and waste products, removing excess substance.
plastids
only plant tissue cells contain organelles green.In addition, there are colorless, yellow and orange plastids.Their structure and functions of the form reflected power plants, and they are able to change color due to chemical reactions.The main types of plastids:
- orange and yellow chromoplasts formed carotene and xanthophylls;
- chloroplasts containing grains of chlorophyll - the green pigment;
- leucoplasts - colorless plastids.
structure of plant cells associated with reaching it by chemical synthesis reactions of organic substances from carbon dioxide and water using light energy.The name of this amazing and very complex process - photosynthesis.Reacted due to chlorophyll, this substance is able to capture the energy of the light beam.The presence of the green pigment is due to the characteristic color of the leaves, grass stems, unripe fruits.Chlorophyll is similar in structure to hemoglobin in animals and humans.
red, yellow and orange coloring of the various organs of plants due to the presence in cells chromoplasts.Their basis is a large group of carotenoids play an important role in metabolism.Leucoplasts are responsible for the synthesis and accumulation of starch.Plastids grow and multiply in the cytoplasm, with it move along the inner shell of the plant cell.They are rich in enzymes, ions, other biologically active compounds.
differences in the microscopic structure of the major groups of living organisms
Most cells resemble tiny sac filled with mucus, calves, grains and bubbles.Often there are different inclusions in the form of solid crystals, minerals, oil droplets, starch grains.The cells are in close contact in the composition of plant tissues, life in general depends on the activity of the smallest units of the structure, forming a whole.
If there is a multicellular structure of specialization, which is expressed in different physiological tasks and functions of microscopic structural elements.They are mainly determined by the location of tissue in the leaves, roots, stems, or generative organs of plants.
distinguish the basic elements of comparison conducted by the plant cell structure with elementary units of other living organisms:
- dense shell characteristic only for plants, formed in fiber (cellulose).In fungi membrane consists of a durable chitin (a special protein).
- plant cells and fungi differ in color due to the presence or absence of a plastid.Such calf as chloroplasts, chromoplasts and leucoplasts, present only in the cytoplasm of the plant.
- There are organelles, which features animals - a centriole (cell center).
- composed only plant cells present a large central vacuole filled with liquid contents.Usually, it saps the colored pigments of various colors.
- spare main compound of the plant organism - starch.Fungi and animals in their cells accumulate glycogen.
Among algae known to many single, free-living cells.For example, such an independent body is chlamydomonas.Although the plants are distinguished from animals by the presence of a cellulose cell wall, but the germ cells are deprived of such a dense shell - this is another proof of the unity of the organic world.
