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The Cell Membrane The cell Membrane is said to be the most important cell organelle. For one thing, it holds the cell together, plus, it regulates homeostasis. Also, the cell membrane contains specific proteins and lipid components that enable it to perform its unique roles for that cell or organelle. It is a semipermeable (a membrane that will allow certain molecules or ions to pass through it by diffusion,) lipid bilayer found in all cells. What the lipid bilayer does is it is the barrier that keeps ions, proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be. The lipid bilayer acts as a barrier because of its structure. Natural bilayers are usually made mostly of phospholipids. (Phospholipids are lipids that are in their simplest form which are composed of glycerol bonded to two fatty acids and a phosphate group.) When phospholipids are exposed to water, they make themselves into a two-layered sheet (a bilayer) with all of their tails pointing in towards the center of the sheet. The center of this bilayer contains almost no water and also excludes molecules like sugars or salts that dissolve in water but not in oil. This assembly can be compared to oil being dropped into water, because it is driven by the same force. It is called the hydrophobic effect.
Cell Membrane Functions The cell membrane has numerous functions, all of them being very important. Aside from being the outer-most part of a cell and considered the barrier between the cell and it's enviornment, it also regulates what goes in and out of a cell. You can think of the cell membrane as the plastic bag holding a sandwich. It protects the lunch by making sure that nothing threatening enters the bag, which would ruin the lunch and could potentially get you sick. The cell membrane also helps the cytoskeleton in the structure of the cell and it transports the materials needed for survival. Here are more examples of the function of the cell membrane: 1.) Acts as a boundary layer to contain the cytoplasm. 2.) selectively permeable to select chemicals that pass in and out of the cell. 3.)The cell membrane protects the interior contents present in the cell from spilling out into the external environment. 4.) The cell also causes small changes in the internal environment by moving stuff across the membrane in a controlled way. These changes are the ways in which the cell responds to events in the outside world. 5.) It protects the cell from drying out. Also, without it, who knows what would happen to that cell!?
The picture provided is an example of a Cell Membrane model! ------------->
Ellen's Desk Ardito Per. 4 3-30-09
Cell Membrane's look/Structre The cell membrane is a delicate organelle on the outer-most part of a cell. It has tiny openings that let in things the cell needs, and prevents anything bad from entering the cell. It also lets out the bad things, (cardon dioxide.) As I aforementioned the Cell Membrane is made up of two layers of molecules (bilayers.) The molecules in the bilayer are called "phospholipids." Each phospholipid has a head and a double tail. The head is called a "hydrophilic," where as the tail is called a hydrophobic. To elaborate upon that, "hydro" means "water," "Philic" means "loving" and "Phobic" means "fearing." (For example when you have a phobia, you have a fear of something.)
Cell Membrane look and Structure continued... When the phospholipids clump together to form the cell membrane, they do so with their hydrophilic heads out, and their hydrophobic tails in. The reason why this happens, rather than the other way around is becasue of the fact that our body is made largely up of water, so the "water- loving " part is faced out. The cell produces many proteins. Some of these proteins are found inside of the membrane bilayer. They double as the "gate keepers" becasue they decide what traffic moves in and out. Here are 4 main kinds of protein involved with the Cell Membrane: Integral Proteins: part of the membrane and make contact with both the inside and the outside of the cell. Transmembrane channel proteins: these are similar to integral proteins but connect to the cytoplasm. Surface Membrane proteins: only on the outer layer of the membrane. Inner membrane proteins: only on the inner layer of the membrane and make contact. These proteins have numerous functions. For example, they can give shape and attach cells together to form tissue, or they can transport molecules into and out of the cell. The possibilitys are (almost) endless for these small wonders!
Above is a picture of an Animal Cell with a detailed picture of the Cell Membrane.
