Peripheral membrane proteins
Peripheral membrane proteins are associated with membranes but do not penetrate the hydrophobic core of the membrane. They are often found in association with integral membrane proteins. In practical terms they can be removed from membranes by means that do not require the disruption of the membrane structure. For example salt washes of membranes are often sufficient to remove peripheral membrane proteins whereas detergent treatment of membranes is often required to remove integral membrane proteins.
An example of peripheral membrane protein is the cytochrome C in the electron transport chain.
The NADH-CoQ reductase complex of enzymes and cytochrome C reductase complex of enzymes are integral membrane proteins of the mitochondrial electron transport chain. The cytochrome c (cyt c) protein is an peripherial membrane protein because it is associated with the other integral membrane proteins but it does not penetrate the inner mitochondrial membrane.