Molecular Biology of the Cell by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter by by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morg

98 PANEL 2–5: Fatty Acids and Other Lipids
COMMON FATTY
ACIDS
These are carboxylic acids
with long hydrocarbon tails.
COOH
COOH
COOH
Hundreds of different kinds of fatty acids exist. Some have one or more double bonds in their
hydrocarbon tail and are said to be unsaturated. Fatty acids with no double bonds are saturated.
– O
– O
O O
C
C
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
oleic
acid
This double bond
is rigid and creates
a kink in the chain.
The rest of the chain
is free to rotate
about the other C–C
bonds.
stearic
acid
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH
CH 2
CH 2
CH
space-filling model
carbon skeleton
CH 2
CH 2
CH 2
UNSATURATED
SATURATED
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 3
stearic
acid (C 18 )
CH 2
CH 2
CH 2
CH 3
palmitic
acid
(C 16 )
CH 2
CH 2
CH 2
CH 2
CH 2
CH 3
oleic
acid (C 18 )
TRIACYLGLYCEROLS
H 2 C O
O
C
HC O
O
C
H 2 C O
O
C
Fatty acids are stored as an energy reserve (fats and
oils) through an ester linkage to glycerol to form
triacylglycerols, also known as triglycerides.
H 2 C
HC
H 2 C
OH
OH
OH
glycerol
CARBOXYL GROUP
If free, the carboxyl group of a
fatty acid will be ionized.
C
O
O _
PHOSPHOLIPIDS
O
O
P
O _
Phospholipids are the major constituents
of cell membranes.
hydrophilic
head
choline
But more usually it is linked to
other groups to form either esters
O
O
CH 2 CH CH 2
C
O
C
or amides.
C
O
hydrophobic
fatty acid tails
space-filling model of
the phospholipid
phosphatidylcholine
N
H
general structure
of a phospholipid
In phospholipids, two of the –OH groups in glycerol are
linked to fatty acids, while the third –OH group is linked
to phosphoric acid. The phosphate is further linked to
one of a variety of small polar groups, such as choline.