Integral and peripheral membrane proteins
Integral Membrane Proteins
These are proteins directly linked to the plasma membrane of cells; they do not have intermediate molecules between them and the plasma membranes. They are also considered as proteins that fully pass through the membrane (carrier proteins and channel proteins).
They do not readily disocciate with the cell membrane, and can therefore only be separated from the plasma membrane through the use of detergents (and other agents) to disrupt the plasma membrane.
Peripheral Membrane Proteins
These proteins are connected to the plasma membrane through intermediate molecules (even integral proteins) by noncovalent interactions. They can be removed fro the membrane fairly easily by simply increasing the salt concentration of the buffer solution which the cells are suspended in.