Mega Molecules, LLC! ! ! ! ! Name: ____________________Hands-On Science with Molecular Models! ! Date: ____________________! ! ! ! ! ! ! ! Hour: ____________________

Molecular Modeling Activity for Cell EnergyTime 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.

MaterialsATP 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

-3The 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.