Phospholipid

A phospholipid is a lipid whose head contains a positively charged (polar?) group that is linked to its two (unpolar?) tails by a negatively charged phosphate group. Both tails consist of a fatty acid, each 14-24 carbon groups long. Phospholipids are used as building blocks of biological membranes.

Due to the polar nature of their head this section of a phospholipid is attracted to water (it is hydrophilic). The non-polar head is not attracted an it is said to be hydrophobic. When placed in water, phospholipids form a bilayer, where the hydrophobic tails line up against each other. This forms a wall with hydrophillic heads on either side. This wall wis partially permeable and very flexible.

See also : biochemistry