Environment hypotonic

Osmotic effects are very important from a physiological standpoint. This is because biological membranes including the membrane of red blood cells behave like semipermeable membranes. Consequently, when red blood cells are immersed in a hypertonic solution (e.g., D5 A NS or D5NS), they shrink as water leaves the blood cells in an attempt to dilute and establish a concentration equilibrium across the blood cell membrane. Thus, when hypertonic solutions are administered into the blood stream, the fluid moves from interstitial and cellular space into the intravascular space. Conversely, when cells are placed in hypotonic environment (e.g., V2 NS), they swell because of the entry of fluid from the intravascular compartment, and may eventually undergo lysis. 

Since the sharks are isotonic to sea water, their cells would burst from the hypotonic environment of a fresh water lake. 

Cell walls in bacteria are porous structures that provide structural integrity and physically protect the cell from swelling and bursting in a hypotonic environment. If the cell wall is removed, the bacteria assume a spherical shape. Cell walls contain specific antigens useful for the diagnosis of some infectious diseases. Inhibitions of the biosynthesis of the bacterial cell wall is the basis for the bactericidal action of penicillin and some other antibiotics. 

The isolation of bacterial DNA described in this experiment, patterned after the work of Marmur (1961), accomplishes these objectives. Bacterial cells are disrupted by initial treatment with the enzyme, egg-white lysozyme, which hydrolyzes the peptidoglycan that makes up the structural skeleton of the bacterial cell wall. The resultant cell walls are unable to withstand osmotic shock. Thus, the bacteria lyse in the hypotonic environment. The detergent, sodium dodecyl sulfate, (SDS, sodium do-decyl sulfate) then completes lysis by disrupting residual bacterial membranes. SDS also reduces harmful enzymatic activities (nucleases) by its ability to denature proteins. The chelating agents, citrate and EDTA (ethylenediamine tetraacetic acid), also inhibit nucleases by removing divalent cations required for nuclease activity. 

Although all eukaryotic cells have much in common, the ultrastructure of a plant cell differs firom that of the typical mammalian cell in three major ways. First, all living plant cells contain plastids. Second, the plasma membrane of plant cells is shielded by the cellulosic cell wall, preventing lysis in the naturally hypotonic environment but making preparation of cell fractions more difficult. Finally, the nucleus, cytosol, and organelles are pressed against the cell wall by the tonoplast, the membrane of the large, central vacuole that can occupy 80% or more of the cell s volume. 

Hemolysis of red blood cell placed in hypotonic environment... 

Based on the strong avoidance and relatively uniform activity in response to all treatments, we conclude that the chemical cue in a garter snake rinse continues to elicit an avoidance response in red-backed salamanders for up to 48-hours in the laboratory, which is in agreement with previous studies by Sullivan et al., (2002). While our results do not support the microbial degradation hypothesis, further research is necessary before we can conclude that microbes are inconsequential to the cue. Other sources of microorganisms, such as the forest floor and soil that harbor a rich and diverse microbial community (Waksman, 1952), should be examined. Also, the hypotonic environment of the distilled water used to collect the snake rinse could have potentially caused cell lysis, destroying any bacteria in the rinse. 

When a biological cell is in a hypotonic environment, the cell interior accumulates water, water flows across... 

The kidney of most fish is primarily involved in hematopoiesis and osmoregulation. Fresh-water fish are hypertonic relative to the water. The continual osmotic uptake of water is balanced by production of as large amounts as 2-4 ml/kg/h of dilute urine. Salt-water fish, on the other hand, are hypotonic relative to their environment, resulting in body water loss. In response, marine species produce much smaller volumes of urine. Large differences exist among different fish species in regard to nephron structure to facilitate these functional responses. These features may influence the renal contribution to drug disposition apprecia-... 

Culture medium osmolality can also increase due to evaporation, since culture flasks are generally not sealed so as to allow equilibrium between culture medium and the C02-air gas mixture. A slightly hypotonic culture medium can be more adequate for open cultures in multiple well plates or in Petri dishes to compensate for evaporation during incubation. To avoid large variations in osmolality during culture, the relative humidity of the culture environment should be maintained near to saturation. 

Holmberg B, Jakobson I, Malmfors T. 1974. The effect of organic solvents on erythrocytes during hypotonic hemolysis. Environ Res 7 193-205. 

The osmotic pressure phenomenon manifests itself in many interesting applications. To study the contents of red blood cells, which are protected from the external environment by a semipermeable membrane, biochemists use a technique called hemolysis. The red blood cells are placed in a hypotonic solution. Because the hypotonic solution is less concentrated than the interior of the cell, water moves into the cells, as shown in Figure 12.14(b). The cells swell and eventually burst, releasing hemoglobin and other molecules. 

The structural strength of the cell wall is a result of pen-tapeptide cross-bridges that link the repeat units to one another (see the figure at the left). Millions of such cross-linkages produce an enormous peptidoglycan molecule, dozens of layers thick, around the bacterium. This thick wall is very rigid. It allows the bacterium to maintain its shape and protects it from bursting if the salt concentration of the environment is too low (hypotonic conditions). 

All aquatic organisms tolerate only a certain range of osmotic values of neighbouring water, which means that they tolerate only certain limited concentrations of dissolved substances, particularly salts [24]. At a higher concentration (hypertonic) the osmotic value of the environment increases and the organisms are damaged or die because of the loss of water drawn from their cells. At too low concentration (hypotonic) the net osmotic flow of water is reversed and water endeavours to overfill and swell the cells, even to bursting point. 

As described for the macroscopic behavior of enzymes immobilized on solid supports (Goldstein, 1977) the rate of catalysis at low substrate concentration could be limited by substrate mass transfer from the bulk medium to the enzyme. Since the ATPase appears to behave similarly to an immobilized enzyme, the phenomenon arises from the relatively slow translocation of ADP in the environment of the enzyme in comparison to its fast transformation on the site. Of course the limitation can be overcome upon saturation in substrate concentration. At steady state, the rate of translocation of substrate is equal to that of catalysis situ, leading to the relative depletion of ADP and/or accumulation of ATP near the enzyme. Support for this view is given by the better utilization of ADP and, to a lesser extent, of GDP with the hypotonically treated chloroplasts (Aflalo, Shavit, 1983). The Km values for ADP and GDP are lower and the Vmax/Km are higher with hypotonically treated chloroplasts, at virtually the same catalytic ability (Vmax). On the other hand, the utilization of Pi remains unaffected, as might be expected for a substrate which is utilized much less efficiently (low Vmax/Km). 

---