‘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 flexible so it can constantly change shapes. It is called mosaic as the different types of proteins are embed in the membrane in different shapes, sizes and patterns, so it resembles a mosaic.
Phospholipids are important components to the structure of the plasma membrane. It forms a bilayer sheet, one layer of the phospholipids has its hydrophilic head (the phosphate which is attracted to water) pointing inwards so that it interacts with the water in the cell cytoplasm and the other layer of phospholipids has its hydrophilic head pointing outwards to interact with the water surrounding all cells. The hydrophobic tail (the fatty acid end of the phospholipid which orients itself away from water and towards fat) of both the phospholipid layers points into the centre of the membrane, protected from the water.
The phospholipid bilayer has important roles in the plasma membrane, such as allowing lipid-soluble substances to enter and leave the cell via diffusion and to stop water soluble substances from entering and leaving the cell. This is also what makes the membrane flexible.
Another component of the plasma membrane are proteins. There are two types; extrinsic and intrinsic. Extrinsic proteins occur on the surface of the