Simple diffusion does not require the hydrolysis of ATP for energy. In the coupled transport of potassium and sodium ions, both potassium and sodium ions are moved by the transporter. Other things being equal, water will move across a membrane to a region where the concentration of solutes is lower. The Golgi apparatus has a double membrane. The nucleus is enclosed by a double membrane.
Chloroplasts possess a double membrane.
If a membrane is impermeable to a particular molecule, then that molecule cannot pass from one compartment to another through the membrane. At equilibrium, individual molecules no longer pass through a permeable membrane. Small, nonpolar molecules can pass directly through the lipid bilayer of the membrane. A red blood cell put into a hypo-osmotic solution will shrink. A plant cell body put into a hyper-osmotic solution will pull away from the cell wall.