In cells, there are thousands of different lipid types. It is likely that they
all have a role to play in cells, yet their functions are not well understood.
The understanding of lipid properties is currently at its best when one
considers the most abundant lipid classes in mammalian cell membranes
such as those comprised of phosphatidylcholine (PC), sphingolipid, and
sterol molecules. Quite substantial work has also been carried out to
clarify the roles of lipid classes that are usually in the minority in cells,
such as phosphatidic acid (PA), phosphatidylserine (PS), and phosphatidylinositol
(PI). While this knowledge is highly valuable, it is
still just the tip of the iceberg. Each of the lipid classes have their own
subclasses and subspecies that differ in a number of seemingly minor
but important ways, such as the degree of unsaturation, the length of
hydrocarbon chains, the chemical details of the polar head group, the
structural modifications due to e.g. oxidative stress, and charge. It
is truly exciting that the information to figure out the amplitude and
the gravity of lipid structural details is now emerging thanks to new
lipidomics tools combined with cell biology and molecular simulations