Download chemistry of fats

CHEMISTRY OF FATS
Lipids are fats, oils and waxes. Fats contain carbon, hydrogen and oxygen, but
the proportion of hydrogen to oxygen is not the same as in carbohydrates.
Because lipids contain very little oxygen, they can yield large amounts of energy
when combined with oxygen.
Goals of this lab:
 Understand the structure of alcohols and fatty acids
 Construct molecular models of fat
 Distinguish between models and actual chemical formulas of fats
 Determine the molecular characteristics of fats
Procedure
Students will work in groups of 4. Each student will be responsible for filling out
his/her own worksheet.
I-
FATS
On a molecular basis, all fats are somewhat similar. Just as
carbohydrates are composed of smaller molecules called
monosaccharides, all fats are composed of smaller molecules. The
smaller molecules in fats are glycerol and fatty acids.
H
H–O–C–H
H–O–C–H
H–O–C–H
H
Glycerol
a. What elements are present in glycerol?
b. Are there any elements in glycerol not present in carbohydrates?
c. What is the molecular formula for glycerol?
d. Build a structural model for glycerol.
e. What is the ratio of hydrogen atoms to oxygen atoms in glycerol?
f. How does this ratio compare to the ratio in carbohydrates?
Fatty Acids
The second molecule which contributes to forming fat is a long
molecule called a fatty acid. Many different fatty acids exist, but all are
similar in many ways.
All fatty acids have a radical group (R, different in every fatty acid) and
a COOH. Therefore we can represent all fatty acids with the general
formula of R—COOH
a. Build butyric acid.
b. What is the molecular formula of butyric acid?
c. Does a 2:1 ratio of hydrogen atoms to oxygen atoms exist in fatty
acids?
FORMING FATS
A fat molecule consists of one glycerol molecule and three fatty acid molecules
joined together.
a.
Attempt to join together the glycerol molecule with three fatty acids. Will
the fat molecule stay together?
b.
It will be necessary to remove three –OH ends from the glycerol molecule
and the –H end from each of the fatty acids’ carboxyl end in order to join the
molecules. Does this enable to join the molecules together? If so, do it.
c.
Fatty acids + glycerol  fat + water
d.
How many water molecules are formed when one fat molecule is
produced?