What are some key components within the cell surface membrane, and what are their functions?

The cell surface membrane is formed of a phospholipid bilayer, in which the hydrophillic phosphate heads point outwards and the hydrophobic tails point inwards. This forms a barrier for large molecules such as glucose from crossing the membrane via simple diffusion. The cell surface membrane also contains transmembrane proteins which form channels across the phospholipid bilayer and control the transport of molecules into/ out of the cell via active transport, or facilitated diffusion