NAME
PERIOD:
DATE:
FATS: CHEMISTRY AND IDENTIFICATION
Fats are present in living organisms. These chemicals make up certain parts of your body. Fats are
often stored when present in excess and serve as an energy source. Fats are important part of our
diet
In this investigation, you will
I. learn that all fat molecules are made up of two kinds of smaller molecules, glycerol and fatty
acids.
1 use swuctural formulas and models to determine how glycerol and fatty acids join to form fat
molecules.
PART A
(
-
FATTY ACIDS
MODELS OF FATS
To better understand the chemistry of
fats, it is helpful to study the small molecules,
which join to make up fats. Fat molecules are
made of two types of molecules, glycerol and
fatty acids.
The second kind of molecule which is
part of a fat is a fatty acid. Many different fatty
acids exist but all are similar in several ways.
Butyric acid, caproic acid, and lauric acid are
examples of fatty acids. Figure 8—2 shows the
structural formulas for these fatty acids.
GLYCEROL
Examine the structural formulas for these three
molecules.
Figure 1
The flgure below shows the structural formula
of glycerol.
I. Which elements are
present in glycerol?
H
K—C-—C—H
H-0
OHH
I
I
H
I
11—0—C—c—c—c—H
I I
H H H
OHH HHH
I I
I
Ii
l I
H—U—c—c—c—c—c—c—H
I
I
I
II
H H HH H
Bulyric Acid
capmic Add
H-C--H
H
glycerol
OH H HH HH HHHH H
II
I I
I I
I I I
I
I I
K—U—c—c—c—c—c —c—c—c—c—c—c—c—il
I I I
I I I I I
I
I
HH HH HH HH[4H H
Lawic Acid
2. Are there any elements in glycerol that
are not in carbohydrates?
4. What elements are present in all fatty
acids?
3. What is the molecular formula for
glycerol?
5. What is the molecular formula for
0
butyric acid? C______ H
C
H___ 0
6. What is the molecular formula for
caproic acid? C_____ H
0
Cut out the glycerol and fatty acid models
molecules. Cut along solid lines only.
7. What is the molecular formula for lauric
0
acid?C___ H
Attempt to construct a fat molecule.
8. How many oxygen atoms are present in
each fatty acid?
Remove three —OH ends from the glycerol
molecule and three —H ends from the fatty
acids. Now join the molecules to form a fat
12. How many glycerol molecules are
needed to form a fat molecule?
9. Note the end of butyric acid containing
the oxygen atoms. This special
arrangement of carbon, hydrogen, and
oxygen is called a carboxyl group.
13. How many fatty acid molecules are
needed to form a fat molecule?
join the leftover
your models.
—
H and —OH ends from
—C—O—H
10. Is the carboxyl group present in all fatty
14. What chemical substance is formed
when —H and —OH ends are joined?
acids?
Circle the carboxyl group for each fatty acid
in Figure I.
II. Do fatty acids and glycerol both contain
a carboxyl group?
COMBINING GLYCEROL AND
FATTY ACIDS TO FORM FATS
15. How many water molecules are formed
when one fat molecule is produced?
16. Many fats exist in living things. The wide
variety of fats is formed by different
combinations of fatty acid molecules. A
change in the type of fatty acid results in
a different type of fat molecule. What
molecule remains unchanged in all fats?
A fat molecule consists of one glycerol
molecule and three fatty acid molecules
joined together.
(
FATS
—
period:
date:
NAME
ANALYSIS
I. Which two molecules make up a fat molecule?
2. List two ways that a fatty acid molecule differs from glycerol.
a.
b.
3. Complete the following table by using “yes” or “no”.
GLYCEROL
Carbon is present
Hydrogen is present
Oxygen is present
Nitrogen is present
Has a carboxy! group
Molecules join to form
fats
One molecule loses 3
OH ends
—
FATTY ACID
CARBOHYDRATE
)
SODaS FOR INVESTICATION B, ‘lATh:
CHEMISTRY AND IDENTIFICATION”
butyric acid
Io_r
In
_1.J
L
0—:j
r
J
LL
{i}
o—
J
L
CapFQiC acid
glycerol
bunt acid
[HI
Users or LABORATORY BIOLOGY:
Investigating Living Systems have the
publishers permission to reproduce this
Charles E. Merrill Publishing
page.
Co., Copyrignt © 1983 by 8e11 &
Howell
24T
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