8 Lipids and Biomembranes!
Lipid: biomolecule that is soluble in organic solvents. Classes of lipids include fats, oils,
nonprotein membrane components and certain vitamins and hormones.
•Unlike proteins, nucleic acids and carbohydrates, lipids are NOT polymers.
•They do, however, have great structural variety.
Functions of lipids:
•Components of biological membranes
Classiﬁcations of lipids, based on their chemical structure:
Fatty acids: Carboxylic acids with long-chain hydrocarbon groups.
•Stearic acid: HO-C(O)-(CH2)16-CH3 --> 18 Carbons, saturated
•Oleic acid: 18 carbons, unsaturated 9-10 bond.
•Linoleic acid: 2 unsaturated double bonds.
•Unsaturated fatty acids pack together less tightly than saturated ones.
Triacylglycerols: Most abundant class of lipids - not components of biomembranes.
•Synthesized and stored in adipocytes - fat
cells, the long term energy deposit of
•Fat content of normal humans (21% men
26% female) allow up to 3 months of
Glycerophospholipids: family of a
amphiphilic (both hydrophobic and hydrophilic
components) with aliphatic tails and polar heads
•They are the major lipid component of
dipalmitoylphosphatidylcholine (DPPC) is
the major lipid component of the lung
surfactant, a substance that is essential for
normal pulmonary function by breaking the
surface tension of water around the alveolar
•This prevents lung collapse.
Spingolipids: Derivatives of sphingosine and a fatty acid residue and saccharide. 8 Lipids and Biomembranes!
Cerebrosides: exist in the brain, where