Mega Molecules, LLC!
!
!
!
Hands-On Science with Molecular Models!
!
!
!
!
!
!
!
!
!
!
Name: ____________________
Date: ____________________
Hour: ____________________
Molecular Modeling Activity for Cell Energy
Time required: one 50-minute period
Introduction
Energy within a cell exists in the form of chemical energy. A source of this chemical
energy is a compound called adenosine triphosphate (ATP). ATP when changed to a
compound called adenosine diphosphate (ADP) releases energy for biological work in
the cell. ADP can be changed back into ATP, but this reaction requires energy. During
cellular respiration, the energy produced from the breakdown of glucose is used to
change ADP to ATP.
In this activity, you will:
• use molecular models to construct models of adenosine triphosphate (ATP) and
adenosine diphosphate (ADP).
• determine similarities and differences between ATP and ADP
• illustrate energy release when ATP changes into ADP
• examine the ATP-ADP cycle.
Materials
ATP Molecular Model Set
Procedure
Part I: The Molecular Structure of Adenosine Triphosphate
Adenosine triphosphate (ATP) is composed of ribose, adenine, and three phosphate
groups. Examine the structural formula of ribose as shown below.
Figure 1: Structural Formula of Ribose
1. What is the molecular formula of ribose? C____ H____ O____
Using the 25mm links, connect the carbon and oxygen atoms according to the structural
formula of ribose. Add the hydrogen atoms to the molecule using the 25mm links.
2. How much larger is the number of hydrogen atoms than oxygen atoms in ribose? ___
______________________________________________________________________
Ribose is a carbohydrate. It is different from glucose, another biologically important
carbohydrate, in that each molecule of glucose has six carbon atoms.
3. How many carbon atoms are in ribose? ___________________________________
Examine the structural formula of adenine below.
Figure 2: Structural Formula of Adenine
4. What is the molecular formula of adenine? C____ H____ N____
In the adenine molecule, the double line indicates a double covalent
bond, the sharing of two pairs of electrons between the bonded
atoms. Build each double bond using 2 of the 51mm links. Build the
carbon–nitrogen and carbon-carbon single bonds using the 25mm
links. Add the hydrogen atoms to the molecule using the 25mm links.
Compare the molecular models of ribose and adenine.
5. What element is present in adenine and not present in the carbohydrate, ribose?
______________________________________________________________________
6. What element is present in the carbohydrate, ribose, and not present in adenine?
_____________________________________________________________________
Examine the structural formula of the phosphate group as shown in Figure 3. Build 3 of
the phosphate groups.
Figure 3: Structural Formula of a Phosphate Group
-3
The phosphate group
has a charge of -3.
7. What is the molecular formula of a phosphate group? P____ O____
An ATP (adenosine triphosphate) molecule is made up of monomers: one ribose
molecule, one adenine molecule, and three phosphate groups. In order to join the
ribose and adenine molecules, you must remove the –OH from the ribose molecule and
the –H from the adenine. The ribose and adenine molecules can now be chemically
joined together. This reaction is called a dehydration synthesis reaction.
Attach one of the three phosphate groups to the ribose molecule using a 25mm gray
link. As shown in Figure 4, use the red high-energy 25mm links to attach the remaining
phosphate groups one at a time to the phosphate group already attached to ribose
molecule. ATP is a very unstable energy-storing molecule because its three negatively
charged phosphate groups are closely packed and repel each other.
Figure 4: The Structure of ATP
Another way to look at the structure of ATP is to see it as an adenosine-containing RNA
nucleotide to which two additional phosphate groups have been added.
8. What molecule is formed when the –OH from the ribose molecule and the –H from
the adenine molecule are joined together? ___________________________________
9. What does the prefix “tri” in triphosphate mean? ____________________________
Part II: The Conversion of ATP to ADP
Adenosine triphosphate (ATP) is the high-energy molecule that stores the energy we
need to power our activities. The bonds between the phosphate groups of ATP can be
broken by hydrolysis. During hydrolysis water activates an enzyme which breaks the
chemical bond. When the terminal phosphate group is cleaved off by hydrolysis, the
red high-energy bond is broken and energy is released to do useful work and ADP
(adenosine diphosphate) is formed. When the terminal phosphate group is cleaved off
ADP, a similar amount of energy is released and AMP (adenosine monophosphate) is
formed.
Figure 5: Conversion of ATP to ADP
Remove one phosphate group from the end of your ATP model.
10. How many phosphate groups are still attached to the original molecule? _________
11. This new compound with one fewer phosphate groups is called adenosine
diphosphate (ADP). What does the prefix “di” mean? _______________________
12. Compare the structural formulas of ADP and ATP and complete the table below.
Description
ADP
ATP
Number of ribose molecules found in
Number of adenine molecules found in
Number of phosphate groups found in
Formed when ATP loses a phosphate group
(place a check mark in the correct column)
Formed when ADP gains a phosphate group
(place a check mark in the correct column)
Part III: Changing ADP to ATP
Energy is continually needed by a cell. ATP is formed from ADP with the addition of
energy. As food in the cells is gradually oxidized, the released energy is used to re-form
the ATP so that the cell always maintains a supply of this essential molecule.
Attach a phosphate group to the ADP molecule using a red high-energy bond to form
the ATP molecule.
13. List the name and number of each molecule forming ADP. ____________________
______________________________________________________________________
______________________________________________________________________
14. List the name and number of each molecule forming ATP. ____________________
______________________________________________________________________
______________________________________________________________________
Teacherʼs Answer Key
1. The molecular formula of ribose is C5H10O5.
2. There are 10 hydrogen atoms and 5 oxygen atoms, a 2:1 ratio.
3. There are 5 carbon atoms in a ribose molecule.
4. The molecular formula of adenine is C5H5N5.
5. The element nitrogen is present in adenine.
6. The element oxygen is present in ribose.
7. The molecular formula of the phosphate group is PO4
8. When the -OH from the ribose molecule and the -H from the adenine molecule are
joined together a molecule of water, H2O, is formed.
9. The prefix “tri” means three.
10. Two phosphate groups are still attached to the original molecule.
11. The prefix “di” means two.
12. Compare the structural formulas of ADP and ATP and complete the table below.
Description
ADP
ATP
Number of ribose molecules found in
1
1
Number of adenine molecules found in
1
1
Number of phosphate groups found in
2
3
Formed when ATP loses a phosphate group
(place a check mark in the correct column)
√
Formed when ADP gains a phosphate group
(place a check mark in the correct column)
√
13. ADP contains 1 ribose molecule, 1 adenine molecule and 2 phosphate groups.
14. ATP contains 1 ribose molecule, 1 adenine molecule and 3 phosphate groups.