ACK’S FATHER LIKES REGULAR BUTTER, HIS OLDER
sister has been putting olive oil on everything since returning from her summer in Italy, and his 82-year-old grandmother, who lives with them, insists on using margarine.
Also, recently, Jack’s mother started buying a lot of foods
containing high levels of omega- 3 fats, because, she says,
they are healthy.
Interested in eating healthy
food, Jack, 16, was open to try-
ing anything, but the chemistry
student in him was wonder-
ing why omega- 3 fat seems
to be the newest synonym
for healthy food. He wanted
to know what the term
“omega- 3” actually meant,
and, for that matter, what
fat was. Also, he wondered
whether fat was the same thing as a
“fatty acid,” because the various food labels do not seem to distinguish
between the two terms, some saying “omega- 3 fats,” others saying
“omega- 3 fatty acids."
Fats and fatty acids
So, what is the difference between fat and fatty acid? In chemical
terms, a fat molecule is known as a triglyceride, which is a triester
formed from glycerol and three molecules of fatty acids. An ester is an
organic compound with the general formula RCOOR’, where R and R’ are
organic groups composed of carbon and hydrogen atoms. In a triglyceride,
three fatty acids are linked through ester bonds to glycerol, which acts
as a backbone for the triglyceride molecule (Fig. 1).
Fatty acids are carboxylic acids with long hydrocarbon tails. The
general structure for a fatty acid is RCOOH, where –COOH is a carboxyl
group and R represents a hydrocarbon side-chain containing 3 to 19
carbon atoms. In a triglyceride, the ester bond is between the carboxyl
group of each fatty acid and one of the three alcohol (–OH) groups of the
glycerol backbone (Fig. 1).
Because so many different types of fatty acids exist and because
triglycerides are composed of three fatty acid side chains—which may
be identical or different—there is an enormous variety of possible triglycerides. Both fats and oils are composed of triglycerides. Fats, such as
Figure 1. Fats and oils, also called triglycerides, are esters composed of
three fatty acid units joined to glycerol. The ester bonds are indicated in red.
O il , an d
By David Warmflash
OH C H
OH C H
OH C H
Glycerol 3 Fatty acid molecules Triglyceride