structure and function of plasma membrane in cells

1094 WordsOct 27, 20135 Pages
ESSAY ‘The structure and importance of the plasma membrane found within and around all cells’ The plasma membrane surrounds all eukaryotic and prokaryotic cells. Eukaryotic cells have membrane bounded organelles whereas prokaryotic cells do not. The plasma membrane forms the boundary between the cell cytoplasm and the environment. Its function are to allow different environments to be established inside and outside the cell. It also controls the movement of substances into and out of the cell. The cell surface membrane which surrounds all cells consists of many components, which together is referred to the fluid mosaic model. It is called fluid because the individual phospholipids can move relative to one another, making the membrane…show more content…
There are four types of passive transport; diffusion, facilitated diffusion, filtration and osmosis. Active transport is not passive as it requires energy to move substances against the concentration gradient. Diffusion, osmosis and active transport of substances in and out of the membrane is very important for all types of cells. One example is the root hair cell. These cells are the exchange surface in plants which are responsible for the absorption of water and mineral ions so without osmosis and active transport this would not be possible. The water is taken up by osmosis through the partially permeable membrane. The root hair cells are surrounded by a soil solution which contains small quantities of mineral ions but mainly water, so has a high water potential (slightly less than zero). The root hair cells themselves contain a high quantity of amino acids, mineral ions and sugars inside them (low water potential). Therefore water will move by osmosis from the soil solution and into the root hair cells, going down the water potential gradient. Cells need to let water-soluble ions and molecules, like glucose and amino acids into them from the environment. However these molecules diffuse through the phospholipid bilayer of the plasma membrane very slowly, so they use another form of passive transport to move these
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