Osmosis biological examples

There are many interesting biological examples of osmosis. A cucumber placed in concentrated brine loses water via osmosis and shrivels into a pickle. People who eat a lot of salty food retain water in tissue cells and intercellular space because of osmosis. The resultant swelling or pufSness is called edema. Water moves from soil into plant roots partly because of osmosis. Bacteria on salted meat or candied fruit lose water through osmosis, shrivel, and die— thus preserving the food. 

Osmotic pressnre is the pressure exerted by dissolved solutes in a solution of water. The stronger the concentration of the dissolved solutes, the greater the movement of water up the concentration gradient, and the greater the osmotic pressure. The significance of osmosis in biology is illustrated by two examples below. 

Another good example is the NEWater project in Singapore shown in Fig. 11 (36). The advanced water reclamation demonstration plant has been operated for 4 yr to produce 10,000 mVd of high-grade water. The source water (feed), which is the effluent from a conventional biological treatment plant, is first treated by microfiltration (MF) and reverse osmosis (RO), and then disinfected by UV radiation, and subsequently adjusted by acid, base, and carbonate in order to have a sufficient alkalinity. The source... 

Those processes can be considered ideal pretreatment for reverse osmosis processes. The concentration and purification of antibiotics by sequential UF and RO,is an example. The removal of antigenic contaminants present in biological mixtures via the combined use of immunocomplexation and ultrafiltration has also been suggested (3 ). ... 

Osmosis has a role in many biological processes, and semipermeable membranes occur commonly in living organisms. An example is the roots of plants, which are covered with tiny structures called root hairs soil water enters the plant by osmosis, passing through the semipermeable membranes covering the root hairs. Artificial or synthetic membranes can also be made. 

The issue of water s uniqueness is often poorly posed. Some of the biological functions of water are simply the consequence of it being in the liquid state, and there is no reason to suppose that other liquids would not perform them equally well. For example, the turgor of plant cells - their inflation with liquid - contributes to the plant s mechanical stiffness. This turgor is a consequence of water uptake by osmosis, which is obviously a generic solvent property. Similarly, any liquid could in principle act as a transport and distribution medium in a vascular network. 

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