Answer:
D. Porine
Step-by-step explanation:
Mitochondria are double membrane-bound cell organelles. The outer and inner mitochondrial membranes are quite distinct from each other with respect to their structures and functions. The outer mitochondrial membrane is permeable to small molecules and ions. Permeability of the outer mitochondria membrane is mainly due to the presence of integral membrane protein porins which make transmembrane channels to allow the free movement of these substances across the outer membrane.
On the other hand, the inner membrane is quite impermeable to most small molecules and ions including protons as it does not have porins. A substance can cross the inner membrane only through specific transporters. The inner membrane has the components electron transport chain and the ATP synthase.