What is selectivily permeable?

A membrane that is "selectively permeable" will allow some molecules and ions to pass through easily (by diffusion or facilitated diffusion), but not others. A membrane may be semipermeable for many reasons - molecule size (small pores can allow small, but not large, molecules to pass through), solubility in the membrane (for instance, fat-soluble molecules can pass through a lipid membrane), or other factors.

First answer by Jeyradan. Last edit by Jeyradan. Contributor trust: 1 [recommend contributor]. Question popularity: 1 [recommend question]