Cell Energy (ATP) Activity
Objective: To understand the molecular structure of ATP and ADP.
Introduction: Energy in organic molecules exists in the form of chemical energy, and is stored in the chemical
bonds. Once the chemical bonds are broken, the energy is released as free energy. A compound called ATP
(Adenosine triphosphate) picks up this free energy. When ATP undergoes a decomposition reaction, it loses a
phosphate group; it becomes ADP, and releases this free energy to the cell for use in cellular processes. ADP is
then converted back to ATP by gaining a phosphate group, a synthesis reaction that requires energy. During a
process called “cell respiration” (to be discussed at a later date), the energy made available from the breakdown
of glucose is used to fuel the reaction of synthesizing ATP from ADP.
In this investigation, you will:
a. use paper models to construct molecules of ATP and ADP
b. determine similarities and differences between ATP and ADP
c. Illustrate energy release when ATP is changed to ADP
d. Study the ATP-ADP cycle
Procedure
Part A:Examining the Chemical Structure of Adenosine Triphosphate
ATP is a nucleotide made up of smaller molecules or subunits- ribose (a 5-carbon sugar), adenine a nitrogencontaining base), and 3 phosphate groups.
I. Ribose molecule
Examine the structural formula of ribose on the right.
1. What is the molecular formula of ribose? (fill in the appropriate
subscripts) C___H___O___
2. How does the number of Hydrogen atoms compare to the number of
Oxygen atoms in ribose? ____:____ (ratio)
Ribose is a carbohydrate (a 5-Carbon sugar). It is different from glucose in
a very important way. Glucose has 6 atoms of Carbon in each molecule.
3. How many Carbon atoms are in ribose? ______
II. Adenine Molecule
Examine the structural formula of adenine (a nitrogen base) on the
left.
4. What is the molecular formula of adenine? C__H__N__
5.
(a) What element is in adenine that is not in carbohydrates?
(b) What element is in a carbohydrate that is not in adenine?
(c) What name is used to describe the H-N-H group?
(d) Is adenine an amino acid? Why or why not?
Name: __________________________
III. Phosphoric acid (a.k.a. Phosphate group)
Examine the structural formula of phosphoric acid on the right.
Note: The letter P represents the element phosphorus
6. What is the molecular formula of phosphoric acid? H__P__O__
Part B: Constructing an ATP molecule
Color code (horizontal and vertical lines) and cut out the models provided
of adenine, ribose and phosphoric acid. Attempt to join the adenine and ribose molecules, as you would
pieces of a puzzle.
Remove the molecule you named in Question #10. DO NOT THROW THEM AWAY- they are NOT
lost!!!! Tape them together on your table.
The adenine and ribose molecules can now be chemically joined. New points of attachment or
chemical bonds are formed. Tape together the adenine and ribose on your table. Examine the
phosphoric acid molecules.
Attach one of the phosphates to the ribose molecule by removing an H from the phosphate.
Attach the remaining phosphates one at a time to the phosphate group already attached to the
ribose.
7. Adenosine is a word made up of a combination of letters from 2 different words. Part of the word comes from
ribose (the letters “os”). Where do the letters “aden” and “ine” come from? ________________________
8. What end parts must first be removed from each molecule in order for adenine and ribose to fit together?
______________________
9. What molecule is formed from the parts that are removed? ___________________. What do you call this
process? __________________
You have now built an ATP molecule. Now label it. Convert it into an ADP molecule and a free
phosphate group.
10. List the 5 molecular “building blocks” that are needed to make one molecule of ATP: (hint: NOT the atoms,
but the actual molecules!) ___________________________________________________________________
11. List the 4 molecular “building blocks” that are needed to make one molecule of ADP: __________________
________________________________________________________________________________________
12. What is required for the chemical combination of these parts? Hint: See models) _____________________
________________________________________________________________________________________
13. Explain how an ATP molecule is changed to an ADP molecule: ___________________________________
________________________________________________________________________________________
14. What is released when ATP is changed to ADP? ______________________________________________
So far, we have seen that ATP can be changed to ADP with energy given off. Energy is required to change ADP
back to ATP, as this is an endothermic synthesis reaction. Where does this energy come from?
The energy comes from a different source. Energy is stored as chemical energy in the bonds of all organic
molecules. Food, such as glucose, contains lots of energy. Glucose is the major source of energy for ATP
formation. Energy is released from food during “cellular respiration”.
Examine the structural formula for glucose shown below.
In respiration, glucose is broken down into 2 identical molecules of a chemical called pyruvic acid. This step is
called glycolysis (glyco = glucose, lysis = break). Glycolysis is the first step in cellular respiration.
15. Count and record the number of chemical bonds in:
a. 1 molecule of glucose: ______
b. 2 molecules of pyruvic acid: ______
Note: be sure to count double bonds as 2 bonds (if you can’t tell if the diagram is showing a single or
double bond, use your knowledge of valence electrons/bonds to determine)
16. Is the amount of energy in 1 glucose molecule the same as the energy in both pyruvic acid molecules?
Why?
________________________________________________________________________________________
17. How is some of this extra energy used? _____________________________________________________
Pyruvic acid is broken down further to yield more energy. Energy released from glucose is used in building more
molecules of ATP.
Analysis Questions:
18. List the name and number of each molecule forming ATP:
________________________________________
19. List the name and number of each molecule forming ADP:
________________________________________
20. How do ATP and ADP differ in:
a. # of phosphate groups: ATP:______ADP________
b. # of ribose molecules: ATP:______ADP________
c. # of adenine molecules: ATP:______ADP________
d. amount of potential chemical energy: ATP:_____________ADP______________
Part B: Constructing an ATP
molecule. Use the template on
the left. First color code the
ribose red, the adenine green,
the phosphate group yellow,
and the O-H and H parts red.
Cut out the models of adenine,
ribose and phosphoric acid.
Attempt to join the adenine and
ribose molecules, as you would
pieces of a puzzle. You must
remove some parts before
joining the other parts. Tape
the parts together except for
one “H”, one “OH”, and one
phosphate group. Place the
cutouts in a folded piece of
paper fashioned as an
envelope.
Part B: Constructing an ATP
molecule. Use the template on
the left. First color code the ribose
red, the adenine green, the
phosphate group yellow, and the
O-H and H parts red. Cut out the
models of adenine, ribose and
phosphoric acid. Attempt to join
the adenine and ribose
molecules, as you would pieces
of a puzzle. You must remove
some parts before joining the
other parts. Tape the parts
together except for one “H”, one
“OH”, and one phosphate group.
Place the cutouts in a folded
piece of paper fashioned as an
envelope.