Visual cell | Article about visual cell by The Free Dictionaryan elementary living system capable of independent existence and self- replication and development; the basis of the structure and life processes of all animals and plants.Cells exist both as independent organisms (protozoans) and as component elements of multicellular organisms (tissue cells).The term “cell” was proposed by the English microscopist R.Hooke in 1. 66. 5. Bulk Email Software Free Download Crackle . The cell is the object of study of a special branch of biology called cytology.Systematic study of the cell did not begin until the 1.The study of life at the cellular level is the basis of contemporary biological research. The structure and functions of each cell show certain characteristics common to all cells, reflecting a common origin from primary organic complexes. The specific features of various cells are the result of specialization in the process of evolution. All cells similarly regulate metabolism, duplicate and use hereditary material, and acquire and utilize energy. At the same time, various unicellular organisms (amoebas, infusorians) differ sharply in terms of size, shape, and behavior. No less diverse are the cells of multicellular organisms. For example, in man, lymphoid cells are small (about 1. Research methods. The first cytological method was the use of microscopy with living cells. Present- day variants of light microscopy, such as phase- contrast, luminescent, and interference microscopy, make it possible to study the shape of the cell, the general structure of some of its elements, the movement of cells, and cell division. The details of cell structure can be revealed only after special contrasting, which is achieved by staining the killed cell. A new stage in the study of cell structure is the use of the electron microscope, which has the advantage of considerably greater resolution of cell structures than the light microscope. The chemical composition of the cell is studied by cytochemical and histochemical methods, making it possible to reveal the localization and concentration of various substances in cellular structures, the intensity of synthesis of these substances, and the movement of the substances within the cell. Cytophysiological methods make it possible to study certain functions of the cell, such as excitation and secretion. ![]() Marine Biology NewsGeneral properties. Every cell has two principal parts—the nucleus and the cytoplasm. Within each of these it is possible to distinguish certain substructures, which differ in shape, size, internal structure, chemical properties, and function. Some of these, called organoids, are vital to the cell and in fact are found in all cells. Others are the products of cell activity and represent temporary formations. The segregation of various biochemical functions takes place by means of these specialized structures, facilitating the accomplishment within the same cell of diverse processes, including the synthesis and decomposition of many substances. Genetic information on the structure of the proteins characteristic of an organism of a particular species is stored in DNA (deoxyribonucleic acid), the principal component of nuclear organoids called chromosomes. ![]() Low background multi-well plates for fluorescence measurements of biological and.Bitdefender total security is now available free to use for a 90 days trial period with new and improved built-in features for maximum protection.Windows 8 Loader by. . Method of detecting a cancerous cell expressing an EGF motif polynucleotide.Molecular Biology, John Wiley & Sons, New York N.MaxBat.RTM. kit), and. Rechercher plus windows vista all editions x86 sp2. Remove water marks from all 32bit and 64bit Windows Server 2008-Windows Vista-Windows 7-RTM. New Windows. Another, most important property of DNA is its capacity for self- replication, which ensures both the stability of the hereditary information and its continuity— that is, its transmission to succeeding generations. Ribonucleic acids, the immediate participants in protein synthesis, are synthesized on limited sections of the DNA molecule (embracing several genes), which act as templates. The transcription of the DNA code is accomplished by the synthesis of messenger RNA (m- RNA). Protein synthesis is, in effect, a reading of information from the RNA template. This process, called translation, involves the participation of transfer RNA (t- RNA) and special organoids, called ribosomes, that are formed in the nucleolus. The size of the nucleolus is a function chiefly of the cell’s ribosome requirement; the nucleolus is, therefore, especially large in a cell that intensively synthesizes proteins. Protein synthesis, the end result of chromosome function, occurs mainly in the cytoplasm. New Biology TechnologyIn the final analysis, proteins (comprising enzymes, components of cell structures, and the regulators of various processes, including transcription itself) determine all aspects of cell life, permitting the cell to preserve its individuality despite its constantly changing surroundings. Whereas the bacterial cell may synthesize about 1,0. Thus, the diversity of intracellular processes increases substantially in the course of evolution. The sheath surrounding the nucleus, which separates the nuclear content from the cytoplasm, actually consists of two membranes, both of which are perforated by pores—specialized areas for the transport of certain compounds from the nucleus into the cytoplasm and vice versa. Other substances pass through the membranes by means of diffusion or active transport, the latter process requiring the expenditure of energy. Many processes occur in the cytoplasm with the participation of the membranes of the endoplasmic reticulum (the principal synthesizing system of the cell), the Golgi apparatus, and the mitochondria. The differences in the membranes of various organoids are determined by the properties of the proteins and lipids that form them. Ribosomes are attached to some of the membranes of the endoplasmic reticulum. These are the site of intensive protein synthesis. This type of granular endoplasmic reticulum is especially well developed in secretory cells or in cells that intensively renew proteins, such as human liver cells, pancreas cells, and nerves. Other biological membranes that are lacking in ribosomes (smooth reticulum) are made up in part of enzymes that participate in the synthesis of carbohydrate- protein and lipid complexes. The products of cell activity may accumulate temporarily in the canals of the endoplasmic reticulum; in some cells the substances are actually transported through these canals. Before being carried out of the cell, substances are concentrated in the lamellar Golgi apparatus, which isolates various cell inclusions, such as secretory or pigment granules, and in which lysosomes are formed (sacs containing hydrolytic enzymes and participating in the intracellular digestion of many substances). The system of canals, vacuoles, and sacs, all surrounded by membranes, acts as an integrated unit; the endoplasmic reticulum can, without interruption, connect to the membranes surrounding the nucleus, unite with the cytoplasmic membrane, and form the Golgi complex. However, these connections are not stable. Often (in many cells, usually), the various membranous structures are discrete and exchange substances through the hyaloplasm. Cell energetics depends to a large extent on the work of the mitochondria. The number of mitochondria varies in different types of cells from dozens to several thousand. For example, there are about 2,0. The outer membrane of the mitochondrion separates it from the cytoplasm. The basic energy conversions of substances occur on the inner membrane. A result of these conversions is the formation of a compound rich in energy—adenosine triphosphoric acid (ATP)—the universal carrier of energy in the cell. Mitochondria contain DNA and are capable of self- replication. However, the autonomy of the mitochondria is relative: their reproduction and activities depend on the nucleus. Various syntheses, the transport and excretion of substances, mechanical work, and the regulation of processes in the cell are performed using the energy of ATP. Certain structures that look like tiny (submicroscopic) tubules participate in cell division and, sometimes, in cell movement. The assembling and functioning of such structures depend on the centrioles. The spindle, operative in cell division, is organized with the participation of the centriole. The spindle, in turn, participates in the translocation of chromosomes and the orientation of the axis of cell division. The basal bodies, derivatives of the centrioles, are necessary for the construction and normal functioning of flagella and cilia, locomotor and sensory formations of the cell whose structure is the same in protozoans and various metazoan cells. The cell is separated from the extracellular medium by the plasma membrane, through which ions and molecules enter the cell and are excreted from it.
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