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Cytolysis
Cytolysis, or osmotic lysis, occurs when a cell bursts due to an osmotic imbalance that has caused excess water to diffuse into the cell. Water can enter the cell by diffusion through the cell membrane or through selective membrane channels called aquaporins, which greatly facilitate the flow of water. It occurs in a hypotonic environment, where water moves into the cell by osmosis and causes its volume to increase to the point where the volume exceeds the membrane's capacity and the cell bursts. The presence of a cell wall prevents the membrane from bursting, so cytolysis only occurs in animal and protozoa cells which do not have cell walls. The reverse process is plasmolysis. In bacteria Osmotic lysis would be expected to occur when bacterial cells are treated with a hypotonic solution with added lysozyme, which destroys the bacteria's cell walls. Prevention Different cells and organisms have adapted different ways of preventing cytolysis from occurring. For example, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasmolysis
Plasmolysis is the process in which cells lose water in a hypertonic solution. The reverse process, deplasmolysis or cytolysis, can occur if the cell is in a hypotonic solution resulting in a lower external osmotic pressure and a net flow of water into the cell. Through observation of plasmolysis and deplasmolysis, it is possible to determine the tonicity of the cell's environment as well as the rate solute molecules cross the cellular membrane. Etymology The term plasmolysis is derived from the Latin word ‘plasma’ meaning ‘matrix’ and the Greek word ‘lysis’, meaning ‘loosening’. Turgidity A plant cell in hypotonic solution will absorb water by endosmosis, so that the increased volume of water in the cell will increase pressure, making the protoplasm push against the cell wall, a condition known as turgor. Turgor makes plant cells push against each other in the same way and is the main line method of support in non-woody plant tissue. Plant cell walls resist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasmolysis
Plasmolysis is the process in which cells lose water in a hypertonic solution. The reverse process, deplasmolysis or cytolysis, can occur if the cell is in a hypotonic solution resulting in a lower external osmotic pressure and a net flow of water into the cell. Through observation of plasmolysis and deplasmolysis, it is possible to determine the tonicity of the cell's environment as well as the rate solute molecules cross the cellular membrane. Etymology The term plasmolysis is derived from the Latin word ‘plasma’ meaning ‘matrix’ and the Greek word ‘lysis’, meaning ‘loosening’. Turgidity A plant cell in hypotonic solution will absorb water by endosmosis, so that the increased volume of water in the cell will increase pressure, making the protoplasm push against the cell wall, a condition known as turgor. Turgor makes plant cells push against each other in the same way and is the main line method of support in non-woody plant tissue. Plant cell walls resist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osmotic Pressure
Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane. It is also defined as the measure of the tendency of a solution to take in a pure solvent by osmosis. Potential osmotic pressure is the maximum osmotic pressure that could develop in a solution if it were separated from its pure solvent by a semipermeable membrane. Osmosis occurs when two solutions containing different concentrations of solute are separated by a selectively permeable membrane. Solvent molecules pass preferentially through the membrane from the low-concentration solution to the solution with higher solute concentration. The transfer of solvent molecules will continue until equilibrium is attained. Theory and measurement Jacobus van 't Hoff found a quantitative relationship between osmotic pressure and solute concentration, expressed in the following equation: :\Pi = icRT where \Pi is osmotic p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lysis
Lysis ( ) is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ''lysate''. In molecular biology, biochemistry, and cell biology laboratories, cell cultures may be subjected to lysis in the process of purifying their components, as in protein purification, DNA extraction, RNA extraction, or in purifying organelles. Many species of bacteria are subject to lysis by the enzyme lysozyme, found in animal saliva, egg white, and other secretions. Phage lytic enzymes (lysins) produced during bacteriophage infection are responsible for the ability of these viruses to lyse bacterial cells. Penicillin and related β-lactam antibiotics cause the death of bacteria through enzyme-mediated lysis that occurs after the drug causes the bacterium to form a defective cell wall. If the cell wall is completely lost and the penicillin was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lysis
Lysis ( ) is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ''lysate''. In molecular biology, biochemistry, and cell biology laboratories, cell cultures may be subjected to lysis in the process of purifying their components, as in protein purification, DNA extraction, RNA extraction, or in purifying organelles. Many species of bacteria are subject to lysis by the enzyme lysozyme, found in animal saliva, egg white, and other secretions. Phage lytic enzymes (lysins) produced during bacteriophage infection are responsible for the ability of these viruses to lyse bacterial cells. Penicillin and related β-lactam antibiotics cause the death of bacteria through enzyme-mediated lysis that occurs after the drug causes the bacterium to form a defective cell wall. If the cell wall is completely lost and the penicillin was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lysozyme
Lysozyme (EC 3.2.1.17, muramidase, ''N''-acetylmuramide glycanhydrolase; systematic name peptidoglycan ''N''-acetylmuramoylhydrolase) is an antimicrobial enzyme produced by animals that forms part of the innate immune system. It is a glycoside hydrolase that catalyzes the following process: : Hydrolysis of (1→4)-β-linkages between ''N''-acetylmuramic acid and ''N''-acetyl-D-glucosamine residues in a peptidoglycan and between ''N''-acetyl-D-glucosamine residues in chitodextrins Peptidoglycan is the major component of gram-positive bacterial cell wall. This hydrolysis in turn compromises the integrity of bacterial cell walls causing lysis of the bacteria. Lysozyme is abundant in secretions including tears, saliva, human milk, and mucus. It is also present in cytoplasmic granules of the macrophages and the polymorphonuclear neutrophils (PMNs). Large amounts of lysozyme can be found in egg white. C-type lysozymes are closely related to α-lactalbumin in sequence and struc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Intoxication
Water intoxication, also known as water poisoning, hyperhydration, overhydration, or water toxemia, is a potentially fatal disturbance in brain functions that results when the normal balance of electrolytes in the body is pushed outside safe limits by excessive water intake. Under normal circumstances, accidentally consuming too much water is exceptionally rare. Nearly all deaths related to water intoxication in normal individuals have resulted either from water-drinking contests, in which individuals attempt to consume large amounts of water, or from long bouts of exercise during which excessive amounts of fluid were consumed. In addition, water cure, a method of torture in which the victim is forced to consume excessive amounts of water, can cause water intoxication. Water, just like any other substance, can be considered a poison when over-consumed in a brief period of time. Water intoxication mostly occurs when water is being consumed in a high quantity without adequate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crenation
Crenation (from modern Latin ''crenatus'' meaning "scalloped or notched", from popular Latin ''crena'' meaning "notch") in botany and zoology, describes an object's shape, especially a leaf or shell, as being round-toothed or having a scalloped edge. The descriptor can apply to objects of different types, including cells, where one mechanism of crenation is the contraction of a cell after exposure to a hypertonic solution, due to the loss of water through osmosis. In a hypertonic environment, the cell has a lower concentration of solutes than the surrounding extracellular fluid, and water diffuses out of the cell by osmosis, causing the cytoplasm to decrease in volume. As a result, the cell shrinks and the cell membrane develops abnormal notchings. Pickling cucumbers and salt-curing of meat are two practical applications of crenation. Plasmolysis is the term which describes plant cells when the cytoplasm shrinks from the cell wall in a hypertonic environment. In plasmolysis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Disruption
Cell disruption is a method or process for releasing biological molecules from inside a cell. Methods The production of biologically interesting molecules using cloning and culturing methods allows the study and manufacture of relevant molecules. Except for excreted molecules, cells producing molecules of interest must be disrupted. This page discusses various methods. Another method of disruption is called cell unroofing. Bead method A common laboratory-scale mechanical method for cell disruption uses glass, ceramic or steel beads, 0.1 to 2 mm in diameter, mixed with a sample suspended in aqueous media. First developed by Tim Hopkins in the late 1970s, the sample and bead mix is subjected to high level agitation by stirring or shaking. Beads collide with the cellular sample, cracking open the cell to release intercellular components. Unlike some other methods, mechanical shear is moderate during homogenization resulting in excellent membrane or subcellular preparations. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contractile Vacuole
A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists and in unicellular algae. It was previously known as pulsatile or pulsating vacuole. Overview The contractile vacuole is a specialized type of vacuole that regulates the quantity of water inside a cell. In freshwater environments, the concentration of solutes is hypotonic, lesser outside than inside the cell. Under these conditions, osmosis causes water to accumulate in the cell from the external environment. The contractile vacuole acts as part of a protective mechanism that prevents the cell from absorbing too much water and possibly lysing (rupturing) through excessive internal pressure. The contractile vacuole, as its name suggests, expels water out of the cell by contracting. The growth (water gathering) and contraction (water expulsion) of the contractile vacuole are periodical. One cycle takes several seconds, depending on the species and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paramecium
'' ''Paramecium'' ( , ; also spelled ''Paramoecium'') is a genus of eukaryotic, unicellular ciliates, commonly studied as a representative of the ciliate group. ''Paramecia'' are widespread in freshwater, brackish, and marine environments and are often very abundant in stagnant basins and ponds. Because some species are readily cultivated and easily induced to conjugate and divide, it has been widely used in classrooms and laboratories to study biological processes. Its usefulness as a model organism has caused one ciliate researcher to characterize it as the "white rat" of the phylum Ciliophora. Historical background ''Paramecia'' were among the first ciliates to be seen by microscopists, in the late 17th century. They were probably known to the Dutch pioneer of protozoology, Antonie van Leeuwenhoek, and were clearly described by his contemporary Christiaan Huygens in a letter of 1678. The earliest known illustration of a Paramecium was published anonymously in Philosophi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Biology
Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and functioning of organisms. Cell biology is the study of structural and functional units of cells. Cell biology encompasses both prokaryotic and eukaryotic cells and has many subtopics which may include the study of cell metabolism, cell communication, cell cycle, biochemistry, and cell composition. The study of cells is performed using several microscopy techniques, cell culture, and cell fractionation. These have allowed for and are currently being used for discoveries and research pertaining to how cells function, ultimately giving insight into understanding larger organisms. Knowing the components of cells and how cells work is fundamental to all biological sciences while also being essential for research in biomedical fields such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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