In the context of cell biology, membrane proteins can be divided into Integral membrane proteins and peripheral membrane proteins.
Integral membrane proteins include
- "transmembrane" proteins (which pass through the cell membrane), which are amphipathic and go completely across the membrane. Ion channels, some receptors, and protein pumps are examples.
- proteins that are attached covalently to fatty acid side chains on the cytoplasmic side (inside) of the membrane.
- extracellular (outside the cell) proteins attached via GPI-linkage or otherwise to the membrane
Integral membrane proteins can be extracted using detergents.
Peripheral membrane proteins are attached through ionic interactions (and can thus be removed by adding salts or changing the pH signifcantly).