Semi-permeable: A membrane that is partially, but not wholly permeable.
The principle of permeation can be illustrated by differences in the diffusion of sugar and water through a membrane. Large sugar molecules in the solution cannot pass through the membrane into the water (top). In contrast, small water molecules easily diffuse through the membrane (bottom). The ability of water to readily cross membranes is vital for establishing equilibrium.
permeation; diffusion . image. Britannica School, Encyclopædia Britannica, 19 Aug. 2024.
Wilhelm Pfeffer
"Wilhelm Pfeffer." Britannica School, Encyclopædia Britannica, 1 Apr. 2024.
Membrane structure
"Membrane structure." World of Biology, Gale, 2010. Gale In Context: Science.