Chloroplasts contain several important membranes, vital for their function. Like mitochondria, chlorplasts have a double-membrane envelope, called the chloroplast envelope. Each membrane is a phospholipid bilayer, between 6 and 8 nm thick, and the two are separated by a gap of 10-20nm, called the intermembrane space. The outer membrane is permiable to most ions and metabolites, but the inner membrane is highly specialised with transport proteins.
Within the inner membrane, in the region called the stroma, there is a system of interconecting flattened membrane compartments, called the lamellae, or thylakoid membrane. These are sites of light absorption and ATP synthesis, and contain many proteins, including those involved in the electron transport chain.