Question: investigate the water potential of potato tissue? Introduction
All cells require essential materials to ensure their survival. Chemical, physical, and biological processes are used to move these materials inside of cells. Similar processes move waste materials outside of cells. These processes can be passive, occurring as a result of basic physical laws and requiring no outside energy from the cell or they can be active, requiring energy expenditure. Since all molecules possess kinetic energy (energy of motion), they are constantly moving enabling the passive transfer of certain substances into and out of cells. Diffusion is the passive movement of molecules from an area of higher concentration to areas of lower concentration. In a closed environment, molecules will disperse until they reach a state a dynamic equilibrium. As the molecules approach equilibrium, the net or overall rate of diffusion begins to slow and occurs equally in all directions. In an open environment, there are no "walls" to confine the molecules so the molecules will always appear to move away from the immediate source. For instance, odours in a confined room persist much longer, whereas odours outside will dissipate more quickly. Molecular weight indirectly affects the rate of diffusion. When a concentration gradient (difference in concentration) exists, the net effect of this random molecular movement is that the molecules eventually become evenly distributed throughout the environment. There are many examples of diffusion in non-living systems – for example, the ability to smell a friend’s cologne shortly after he or she has entered the room. It can also be seen if you drip food colouring or ink into a clear glass of water. Water will let other molecules move among the water molecules so freely that the water carries or transports them. The diffusion of particles into and out of cells is regulated by the plasma membrane, which constitutes a physical barrier. In general,...
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