Did you know…the border of your cell is liquid?

Believe it or not, the barrier surrounding the cell (cell membrane) isn’t actually solid. It is an oily substance! You see, a cell needs to be able to take in and send out substances, all in specific amounts. If the membrane were solid, the cell would need to have holes, which would cause good substances to leak out and bad substances to get in. Because the membrane behaves like a liquid, it can allow channels to poke through it, to open and close when needed, without leaking. It is thick and stops harmful substances from entering at will.

The cell membrane has this wonderful effective barrier by using lipids (oil) that are semi-permeable (they let some things in but not others). These special oils are called phospholipids. Phospholipids have two parts: a hydrophilic head (likes water) and a hydrophobic tail (repels water). The water-loving head of the phospholipid faces outward toward the watery surroundings of the cell. The hydrophobic tail faces inward into the top inner half of the membrane, away from water. The same thing happens on the inner layer of the membrane. The heads face the watery inside of the cell, while the tails points inward into the bottom half of the thick cell membrane. So, the tails from both the outer and inner layers meet in the middle.

There are 2 more parts that make up the cell membrane, Proteins and carbohydrates. Come back next week to learn about those!