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fluid balance

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P4- Describe the processes by which materials move into and out of cells The first process I am going to write about is diffusion. The physics definition of this is intermingling of substances: the random movement of atoms, molecules, or ions from one site in a medium to another, resulting in complete mixing (http://uk.encarta.msn.com/dictionary). To explain this is in more detail it is when Materials move into and out of cells, it is also the movement of molecules from a region of high concentration to a region of low concentration. Molecules, atoms and ions are in a random constant motion and that this is most marked in gases but also in liquids, this is because they are further apart. ...read more.


For this to happen the concentration must be different; this is known as concentration gradient. Concentration gradient is the difference between opposing concentrations. The greater the concentration gradient, the rate of diffusion will be faster, however it will not happen instantly. This is because the numbers of molecules become more evenly distributed, but the net movement of molecules will slow down and eventually come to a stop. The cell membrane is a very selective "molecular gatekeeper". It contains a continuous layer of lipid and protein molecules that act as a selective barrier to regulate the cell's chemical composition. The passage of most dissolved substances is regulated via special protein molecules, called transport or carrier proteins, which are embedded within the thickness of the layer. ...read more.


Meanwhile, the carrier protein uses the energy to change its shape, or configuration, flipping the substance through the membrane and releasing it on the other side. Some substances, such as sodium and potassium ions, have their own dedicated carrier proteins and pumping mechanisms. (http://uk.encarta.msn.com/encyclopedia). Material will also move through the body because of osmosis. The physics definition of osmosis is slow change in concentration: the diffusion of a solvent through a semi permeable membrane from a dilute to a more concentrated solution (http://uk.encarta.msn.com/dictionary) so in a simpler term it is a net movement of water molecules through the cell membrane and then moves down the concentration gradient like diffusion. ?? ?? ?? ?? Carla Cooper Unit 13: Fluid Balance for Health and Social Care Task1 9th November 2007 6 ...read more.

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