PANEL 2–5 Fatty Acids and Other Lipids
COMMON FATTY
ACIDS
TRIACYLGLYCEROLS
O
These are carboxylic acids
with long hydrocarbon tails.
COOH
COOH
COOH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH2
CH2
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
palmitic
acid
(C16)
CH2
CH3
stearic
acid (C18)
CH3
oleic
acid (C18)
H2C
O
HC
O
H2C
Fatty acids are stored as an energy reserve (fats and
oils) through an ester linkage to glycerol to form
triacylglycerols, also known as triglycerides.
C
O
H2C
OH
C
HC
OH
O
H2C
OH
C
O
glycerol
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
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.
oleic
acid
space-filling model
carbon skeleton
UNSATURATED
CARBOXYL GROUP
stearic
acid
SATURATED
Phospholipids are the major constituents
of cell membranes.
PHOSPHOLIPIDS
hydrophilic
group
If free, the carboxyl group of a
fatty acid will be ionized.
O
O
O
C
O
choline
_
O
P
_
O
CH2
CH
CH2
But more usually it is linked to
other groups to form either esters
O
C
O
C
hydrophobic
fatty acid tails
or amides.
space-filling model of
the phospholipid
phosphatidylcholine
O
C
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 (alcohols).