Inner mitochondrial membrane
The inner mitochondrial membrane is made up of many folds called cristae which greatly increase the surface area of this membrane. Along the membrane are a range of transport proteins which transport molecules into the matrix of the mitochondria. These molecules may be necessary for enzymes in the matrix. The inner mitochondrial membrane is also the site of oxidative phosphorylation and has enzymes embedded in it which are required for this process to produce ATP. 
- ↑ Alberts, B (2008). Molecular Biology of The Cell. 5th ed. New York: Garland Science. 817.