Literally translated: water-liking. The opposite of hydrophobic.
Hydrophilic is a chemical term describing a group that has a high affinity for water. This is generally due to favorable electrostatic
interactions (as would be observed around ions
) or through hydrogen bond
The hydrophilic nature of certain protein sidechains
is important to understanding their localization in protein structures. Hydrophilic groups prefer to be in contact with water, and are therefore infrequently found buried inside the protein. When they are buried, they are usually making hydrogen bonds
or salt bridges
that give a comparable interaction energy to that of being solvated
Hydrophilic groups also help determine the nature of micelles
and lipid bilayers
. Because phospholipids
- having a hydrophobic
and a hydrophilic domain, they can form structures where only the hydrophilic region sees water while the hydrophobic region is protected from it. The two stable geometries are a micelle - a ball with a hydrophilic surface and a hydrophobic core, and a bilayer - a planar surface with the hydrophobic core sandwiched between two hydrophilic surfaces.