(eli5) What is the role of the heads in the cell membrane?

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I know they interact with water but why?

In: Biology
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Are you asking about the polar heads of the glycerophospholipids? Basically these are molecules that have a ‘head’ end and a ‘tail’ end. The tail is non-polar and thus adverse to water – like oil – and the head end is the opposite.

The reason that this happens is kind of complicated, but in a nutshell, molecules can have an uneven electrical charge because of the shape of the molecule and the distribution of atoms in it. So ‘polar’ molecules have a slightly positively charged side and a slightly negatively charged side, like itty bitty magnets. Water happens to have this property, molecules that have it interact better with water than molecules which don’t. Substances that are non-polar don’t dissolve well in water, like oily substances, which – surprise – are made of non-polar molecules.

So glycerophospholipids have an end which is polar and an end which is non-polar; an end which is a water-interactive magnet and an end which isn’t. Because of that they really like to line up in a circle with all their ‘heads’ sticking in the water and all their ‘tails’ out of the water. This makes it a good material to build cell membranes out of