Top Membrane Flashcards

A membrane is a thin barrier between two spaces. In biology, it usually refers to the cellular membrane, or the microscopic sheet that separates the inside of the cell from the outside. Cell membranes have a very simple design that works perfectly to allow water and other small and polar molecules in and out, while excluding larger, nonpolar molecules.

The membrane of a cell has two layers, each made up of a long sheet of phospholipid molecules. The phospholipids have a polar phosphate at one end, which attaches to water (that’s where the “phospho-”) comes from. At the other end they have a fatty tail, or “lipid,” which repels water and attaches to other lipids. So when two of those layers come together, they act a little like double-sided tape, each side sticking to the water around it, but still creating a barrier between the inside and outside of the cell. The membrane is what allows the cell to regulate what comes in and what stays out, which keeps them alive and lets them function.
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