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Cell Surface Membrane.

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Cell Surface Membrane. The cell surface membrane: a unique barrier that divides the activities occurring inside the cell from the world outside, at the same time acting as a semi-permeable, letting certain molecules and substances to pass, while preventing others. Although its functions seem to be simple, its configuration and the activities that transpire to help it carry out its purpose are far more complicated. But to understand how it works we must first understand, its structure. The main outline of the membrane consists of phospholipids, which contain a hydrophobic hydrocarbon and a hydrophilic phosphate and its due to this fact that the membrane obtains its shape from. ...read more.


Extended out from the surface membrane is tree like structure called glycolipids, (also there are similar tree like structure that extend from the proteins with are called glycoproteins). In all the structure of the membrane should look like figure 2. Although the phospholipids are packet together in a regular arrangement, there are minuscule gapes in-between them, this provides the first manner of penetration of the membrane (and by far the simplest). Small molecules, like water have the ability to slip though these gaps and then into the actual cell its self. Yet other substances are too large to fit though these gaps, so they use the large proteins which are located in-between the phospholipids. ...read more.


(The random movement of molecules causes the to coiled together, which consequently will cause move faster and eventually this will result in net movement. Therefore the molecules will spread out). However the other substance in excess, so they have to be pulled in, through a process called active transport, this is the transport of molecules against the concentration. Active transport needs energy, and it obtain the energy form the brake down of ATP. For example look at figure 4, the ion attaches its self to the carrier to the carrier protein, but for the protein to change shape and pull the ion in, it needs energy, so it begins to brake down the ATP into ADP which as a result releases energy, this allows the molecule to change shape and draw the ion in to the cell. ...read more.

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