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David L. Nelson and Michael M. Cox
LEHNINGER
PRINCIPLES OF BIOCHEMISTRY
Sixth Edition
CHAPTER 10
Lipids
© 2013 W. H. Freeman and Company
Lipids
Lipids are a family of compounds that are
relatively insoluble in water.
Lipids play major roles in:
energy storage
membrane structure
Other roles of lipids:
enzyme cofactors
light-absorbing pigments
hormones
signal transduction molecules
Lipids often contain fatty acids molecules.
Fatty acids are carboxylic acids with hydrocarbon
chains from 4 to 36 carbons long.
The most common biological fatty acids have an even
number of carbons between 12 and 24 carbons.
Fatty acids can be saturated (no double bonds)
or unsaturated (containing double bonds)
double bonds are in the cis configuration.
Nomenclature:
16:0 is a 16 carbon fatty acid with no double bonds
20:2 (D9,12) is a 20 carbon fatty acid with double
bonds after C-9 and C-12 (C-1 is COOH)
Packing of fatty
acids into stable
aggregates
Triacylglycerols contain
three fatty acids esterified
to a glycerol backbone
Triacylglycerols are stored energy in
fat cells and plant seeds
The greater the percentage of saturated fatty acids in
food fats the higher the melting temperature
Waxes are esters of long chain fatty acids
Common types of storage and membrane lipids
Glycerophospholipids, the main lipid component of biological membranes,
contain two fatty acids esterified to a glycerol phosphate backbone
Structure of phosphatidylcholine
Glycerophospholipids with ether-linked fatty acids
Abundant in
the heart
Important in
inflammatory
response
Archaea contain unique membrane lipids
Sphingomyelin is similar in structure to phosphatidylcholine
Glycosphingolipids
as determinants of
blood groups
Glycosphingolipids contain
the blood group antigens
present on the surface of red
blood cells
Blood Groups
The carbohydrates on certain sphingolipids determine
your blood group, affecting the blood type you can
receive in a transfusion.
These sphingolipids are on the surface of erythrocytes.
Type A individual has A antigens and anti-B antibodies
Type B individual has B antigens and anti-A antibodies
Type AB individual has A and B antigens and neither
anti-A nor anti-B antibodies
Type O individual has O antigen and both anti-A and
anti-B antibodies
Example: Type A individual cannot receive Type B blood.
Antigen-antibody interaction causes agglutination
The specificities of
phospholipases, enzymes that
cleave glycerophospholipids
Sterols have four fused carbon rings
Cholesterol is the main sterol in animal tissues
Bile acids are synthesized from cholesterol
Bile acids aid in emulsification of dietary fat in the intestine
Arachidonate is the precursor for eicosanoid hormones
Eicosanoids are involved in pain, fever, inflammation
Other sterols are synthesized from cholesterol
Vitamin D is produced in the skin by UV
irradiation of 7-dehydrocholestreol
Vitamin A is a lipid belonging to the isoprenoid family
Some biologically important isoprenoids