The Effect Of Selective Permeability On The Cell

1435 WordsJun 18, 20156 Pages
INTRODUCTION: If a cell is to perform its functions it must maintain a steady state in the midst of an ever changing environment. This steadiness is maintained by the regulation of movement of materials into and out of the cell. To achieve this control, cells are bounded by a delicate membrane that differentiates between different substances, slowing down the movement of some while allowing others to pass through. The membrane is said to be differentially permeable since not all substances penetrate equally well. Selective permeability is a characteristic of healthy, intact cells. When a cell is seriously damaged, the membrane becomes permeable to virtually to everything and substances can move freely in and out of the cell. (Marieb 2013) Movement of these molecules (the dissolved organic and inorganic molecules in the cell’s environment) involves diffusion--a spontaneous process by which molecules move from a region of higher concentration to that of a lower concentration that is, down or along their concentration gradient. (Marieb 2013) The ability to smell a friend’s cologne is an example of diffusion. (Marieb 2012) Diffusion is an important means of a passive membrane transport that is, it does not require any input of energy. Since the driving force for diffusion is the kinetic energy of the molecules themselves, the speed of diffusion is influence by the molecular size; the smaller the molecular size, the faster the diffusion and temperature; the warmer the faster.
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