branch CELLS

Coming from ORGANELLES
=Cell Membrane= ''(also plamsa membrane)'' [image:http://i.imgur.com/ibBVHJv.png?2] The membrane surrounding the cell and most organelles is made largely of phospholipids. A '''phospholipid''' is a chemical group that consists of a phosphate head and lipid tail(s). The phosphate groups are charged and are attracted to water, they are hydrophilic (water loving). The lipid groups are attracted to each other and do not interact with water, they are hydrophobic (water hating). As a result, the phospholipids arrange themselves into a double layer in which all the hydrophobic lipid tails are buried in the centre. Thus the cell membrane if often referred to as a '''phospholipid bilayer'''. ===Other components of the cell membrane:=== [image:http://i.imgur.com/smq8iNU.png?1] • Cholesterol - a type of lipid (hydrophobic) found among the hydrophobic tails in the lipid bilayer. Cholesterol regulates the fluidity of the membrane. • Proteins - can function as enzymes to speed up chemical reactions, act as receptors for for signalling, or transport materials across the membrane. Proteins can be found within the lipid bilayer (integral proteins) or on either side. • Carbohydrates -are sometimes found attached to proteins or lipids on the outside of a cell membrane. It plays an important role in cell recognition, helping the body to distinguish between self and non-self. ==Fluid Mosaic Model== [image:http://i.imgur.com/gbyMLAK.gif] The cell membrane is often described a "fluid mosaic" because phospholipids and proteins embedded within the membrane can move freely within the layer. The membrane acts like a two-dimensional fluid through which small clusters of proteins and lipids (called ''lipid rafts'') move like a raft does through the waters surface.
Credit: Ben Himme