Download Chemistry of Fats and Carbohydrates

Chemistry of Fats and Carbohydrates
All living things are composed of many different kinds of chemical molecules. Two very important
chemical molecules are fats and proteins. Both make up parts of living cells. Fats are a part of all cellular
membranes. They also may be stored within a cell as an energy source. Proteins form part of almost all
structures within a cell. Therefore, they are essential for cell growth and repair. Also, many proteins are
enzymes and are involved in cellular chemical reactions.
In this investigation, you will
a) Learn that all fat molecules are made up of two kinds of smaller molecules, glycerol and fatty
acids
b) Use structural formulas and models of glycerol and fatty acids to determine how these molecules
join together to form fat molecules
c) Learn that all protein molecules are made up of smaller molecules called amino acids.
d) Use structural formulas and models of amino acids to determine how these molecules join together
to form protein molecules.
Materials
Scissors
Procedure
Part A. Fats
To better understand the chemistry of fats, it is helpful to study first the small molecules which join to
make up fats. Fat molecules are made up of two different kinds of chemical molecules. These are glycerol
and fatty acids.
Glycerol
 Examine the structural formula of glycerol.
1. What elements are present in glycerol?
___________________________________________
2. Are there any elements in glycerol that are not in carbohydrates?
__________________
3. What is the molecular formula for glycerol? (add the number of atoms of each element and record
the totals) ______________________
4. As in carbohydrates, are there twice as many hydrogen atoms as oxygen atoms in glycerol?
_____________________________________________________
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.
 Examine the structural formulas for the above three molecules
5. What elements are present in all fatty acids?
_________________________________________________
6. a) What is the molecular formula for butyric fatty acid? _____________________
b) What is the molecular formula for caproic fatty acid? ____________________
c) What is the molecular formula for lauric fatty acid? _____________________
7. Are there twice as many hydrogen atoms as oxygen atoms in a fatty acid? ______
8. What pattern does appear in the fatty acid molecules regarding the number of oxygen atoms?
________________________________
9. Note the end of butyric acid containing the oxygen atoms. This special end arrangement of carbon,
hydrogen, and oxygen is called a carboxyl group. Is the carboxyl group
present in all fatty acids shown? _______________________
10. a) List similarities between glycerol and fatty acids. __________________
___________________________
b) Do fatty acids and glycerol both contain a carboxyl group? ______________
Combining Glycerol and Fatty Acids to Form Fats
A fat molecule consists of one glycerol molecule and three fatty acid molecules joined together.
 Cut out the glycerol and fatty acid paper model molecules from page 39. You may want
to paste the page on lightweight cardboard before cutting out the models. Cut along the
solid lines only. Attempt to construct a fat molecule.
11. Will the fat molecule fit together as pieces in a puzzle? ___________________

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. a) How many glycerol molecules are needed to form a fat molecule? _________
b) How many fatty acid molecules are needed to form a fat molecule? _________

Join the leftover –H and –OH ends from your models.
13. What chemical substance is formed when the –H and –OH ends are joined?
______________________
Production of a fat molecule is a chemical reaction. A chemical shorthand way of expressing the
formation of a fat is as follows:
Glycerol + Fatty Acids Molecules  Fat + Water molecules
14. How many water molecules are formed when one fat molecule is produced?
Many fats exist in living things. The wide varieties of fats are formed by different combinations of
fatty acid molecules. ________________
15. What molecule remains the same in fats? _________________________
Part B. Proteins
Proteins are complex molecules made up of simpler building blocks or smaller molecules. The small
molecules which make up protein molecules are called amino acids.
Glycine
Alanine
Valine
threonine
Amino Acids

Examine the structural formulas of the four representative amino acids shown here.
16. The elements nitrogen (N) is present in amino acids. Is nitrogen present in fats and carbohydrates?
(Use structural formula as a guide) ____________
17. a) What is the molecular formula for the amino acid glycine? C__H__O__N__
b) What is the molecular formula for the amino acid alanine? C__H__O__N__
c) What is the molecular formula for the amino acid threonine? C__H__O__N__
18. Are the molecular formulas for all the amino acids the same? _________
19. What end arrangement of atoms is present in amino acids that is also present in fatty acids?
___________________________
20. Another end arrangement is all amino acids consist of a nitrogen atom of two hydrogen atoms.
This group is called an amino group. Do the structural formulas for all amino acids have amino
groups? _____________
Combining Amino Acids to Form Proteins
Protein is composed of many amino acids joined together chemically.

Cut out the four amino acids models from page 39. Cut along the solid lines only. Attempt to join
the amino acids. Will the protein molecule fit together?

Join the molecules by removing as many –OH groups and –H groups as needed from the amino
acids. All four amino acid molecules can be joined in this manner to form a protein. Join them in
this order Valine (val) – threonine (thr) – alanine (ala) – glycine (gly).

Rejoin the leftover –OH and –H ends.
21. What chemical substance is formed when the –OH’s and –H’s are joined?
Chemist express the joining of these amino acids as followed.
Val + Thr + Ala + Gly  Protein + Water
22. How many molecules of water are formed when four amino acids join together?
Other combinations of amino acids result in the formation of different proteins.
 Construct a protein different from the one above
Analysis
1.
2.
3.
4.
5.
6.
7.
8.
9.
a) What two molecule types are needed to form a molecule of fat?
b) How many of each type of these molecules are needed to form a molecule of fat?
What chemical elements are found in all fats?
List two ways that fatty acids differ from glycerol.
a)
b)
What small molecule type is needed to form a large protein molecule?
What chemical elements are found in all proteins?
List two ways that amino acids differ from fatty acids.
a)
b)
How might one amino acid differ from another?
How might one protein differ from another? (For example, consider cow muscle proteins and
human muscle proteins.)
Complete Table 8-1 with yes and no answers.
Table 8-1. Summary of Glycerol, Fatty Acids and Amino Acids
Glycerol
Fatty Acids
Carbon present
Hydrogen present
Oxygen present
Nitrogen present
Twice the amount of
hydrogen as oxygen
Has a carboxyl group
Has an amino group
Molecules join to form
protein
Molecules join to form
fats
One molecule looses 3
OH ends
Amino Acids