An+annotated+diagram+of+a+plasma+membrane+and+information+on+it.

=**The Plasma Membrane**=


 * Figure 1:** Diagram of the plasma membrane

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All living cells have a plasma membrane. If they do not have a plasma membrane they are not classified as a cell. The plasma membrane (also known as the cell membrane) is the outermost barrier of a cell that separates the cytoplasm from other cells and its environment. The plasma membrane regulates what enters and leaves the cell.


 * Phospholipids **: These lipids are called phospholipids because instead of the usual three fatty acid chains there are only two. Phospholipids are divided into a hydrophilic head and a hydrophobic tail. The head is hydrophilic which means they are attracted to water whereas the tail is hydrophobic, which means they are repelled by water. When a phospholipid is placed in water, their hydrophilic heads are attracted to the water and their tails are forced to stick together because they do not dissolve, this forms a bilayer.


 * Glycoprotein: **Proteins with carbohydrates attached are called glycoproteins. The glycoproteins are attached to the bilayer of the plasma membrane and aid in the transport of waste and nutrients. They also help shape the cell and help transport molecules across the membrane.


 * Carbohydrate: ** Carbohydrates are an integral part in the formation of the plasma membrane. The carbohydrates found in the plasma membrane are usual found in the form of oligosaccharides (3-10 sugar molecules). These oligosaccharides help with cell interaction by guiding hormones to their receptors.


 * Globular protein: **Globular proteins act as enzymes and catalyze organic reactions within the plasma membrane. The globular proteins transport molecules through the membrane, and act as regulators within the membrane. Proteins also perform many functions like pumping substances in and out of the cell, attaching to other cells, forming borders to keep other proteins in one specific part of the cells.


 * Glycolipid: **Phospholipids with carbohydrates attached are called glycolipids. Glycolipids are membrane components composed of lipids that are covalently bonded to monosaccharides or polysaccharides.


 * Cholesterol: **The cholesterol maintains the integrity of the cell membrane as it adds firmness. They also prevent the plasma membrane from becoming overly fluid. Cholesterol is an //amphipathic molecule //, meaning, like phospholipids, it contains a hydrophilic and a hydrophobic portion.