Question

What characteristic makes a cell membrane selectively permeable ?

Answer 1

The cell membrane is made up of a bilayer of phospholipids. These are phospholipid molecules. Each phospholipid has a hydrophilic head and two hydrophobic fatty acyl chains. The bilayer is arranged in such a way that the heads face the exterior, that is, towards the cytoplasm and the ECM while the tails form the central layer. This bilayer at various places is interspersed with intrinsic and extrinsic proteins that allow selective ions and molecules to pass through them. This is because ions and other polar molecules or charged molecules cannot pass through the lipid bilayer. So, their passage is regulated by the proteinand cholesterol molecules embeddedin the bilayer .