Biology Reference
In-Depth Information
FIGURE 5.1
Amphipathic mole-
cules form micelles when their critical
micelle concentration is exceeded.
MONOMERS
MICELLE
sphingolipids employ a nitrogen ester (amide). Even sulfur esters (thioesters) are not
uncommon (
Figure 5.2
).
One important example of an ester-containing lipid is triacylglycerol, a non-polar lipid
called either a fat (if solid at room temperature) or an oil (if liquid at room temperature).
A triacylglycerol has 3 fatty acids attached to a glycerol via ester bonds. A fat has predom-
inantly high T
m
saturated fatty acids while an oil has predominantly low T
m
unsaturated
fatty acids. Esters can be hydrolyzed by boiling in NaOH (soda ash) or KOH (caustic
potash). Boiling animal fat in KOH produces glycerol (also called glycerine) and 3 K
รพ
salts
of fatty acids (
Figure 5.3
). Boiling animal fat with caustic potash is the original method for
making soap.
The term used for making soap by hydrolyzing a fat or oil in a strong base is saponifica-
tion. It is clear that saponification is a process that has been used for a very long time
[1]
,at
O
ester
C
O
R
1
R
2
O
amide
C
R
2
N
H
R
1
O
thioester
C
S
R
1
R
2
FIGURE 5.2
Types of bonds attaching fatty acids in complex lipids.
