1. Carbon: Transformations in Matter and Energy
Environmental Literacy Project Michigan State University
Plants Unit Activity 3.3 Molecular Models for Potatoes Cellular Respiration
Image Credit: Craig Douglas, Michigan State University

2. Where does the carbon in CO2 come from?
How do water, oxygen and carbon dioxide move into and out of plants in the dark?
water
oxygen
carbon dioxide
Image Credit: Craig Douglas, Michigan State University
Have students examine cellular respiration at macro and atomic/molecular scales.
Open 3.3 Molecular Models for Potato Cellular Respiration PPT.
Use slide 2 to remind students of the important inputs and outputs for this process.
Use slide 3 to establish the problem for this lesson.
Where does the carbon in CO2 come from?

3. How do plant cells get the energy they need to move and function?
Image Credit: Craig Douglas, Michigan State University
Have students examine cellular respiration at macro and atomic/molecular scales.
Open 3.3 Molecular Models for Potato Cellular Respiration PPT.
Use slide 2 to remind students of the important inputs and outputs for this process.
Use slide 3 to establish the problem for this lesson.

4. Plants use food in two ways
Materials for growth: Biosynthesis
Food
To Cells
Energy: Cellular respiration
Have students think about cellular respiration at an atomic-molecular scale.
Use the slides in the PPT to have the students discuss what is happening during cellular respiration before the molecular modeling activity.
Use Slide 4 to teach students that plants use food in two ways: materials for growth (biosynthesis), and energy (cellular respiration). This is shown at the atomic/molecular scale. Note that cellular respiration occurs in all cells.
Show students slide 5 to have them think about where atoms are moving from and moving to during cellular respiration.
Show slide 6 to explain that atoms and molecules are moving so that plants can get energy through cellular respiration: Plants need glucose and oxygen as reactants, and they must get rid of carbon dioxide and water as waste.
Show slide 7 to explain a somewhat simplified version of movement of all these materials through the potato plant.
Show slide 8 to zoom into a stem cell in the potato plant to illustrate cellular respiration at the cellular scale. Glucose and oxygen enter the cell; carbon dioxide and water leave—and cell gets energy to function!
Have them look at the Potato 11 x 17 Poster to discuss the parts of a potato plant involved in cellular respiration on a macroscopic scale. Tell students that all parts (all cells) of a potato plant undergo cellular respiration.

5. Where are atoms moving from?
The movement question
Where are atoms moving from?
Where are atoms moving to?
Image Credit: Craig Douglas, Michigan State University
Have students think about cellular respiration at an atomic-molecular scale.
Use the slides in the PPT to have the students discuss what is happening during cellular respiration before the molecular modeling activity.
Use Slide 4 to teach students that plants use food in two ways: materials for growth (biosynthesis), and energy (cellular respiration). This is shown at the atomic/molecular scale. Note that cellular respiration occurs in all cells.
Show students slide 5 to have them think about where atoms are moving from and moving to during cellular respiration.
Show slide 6 to explain that atoms and molecules are moving so that plants can get energy through cellular respiration: Plants need glucose and oxygen as reactants, and they must get rid of carbon dioxide and water as waste.
Show slide 7 to explain a somewhat simplified version of movement of all these materials through the potato plant.
Show slide 8 to zoom into a stem cell in the potato plant to illustrate cellular respiration at the cellular scale. Glucose and oxygen enter the cell; carbon dioxide and water leave—and cell gets energy to function!
Have them look at the Potato 11 x 17 Poster to discuss the parts of a potato plant involved in cellular respiration on a macroscopic scale. Tell students that all parts (all cells) of a potato plant undergo cellular respiration.

6. Which atoms and molecules move during cellular respiration?
water
carbon dioxide
oxygen
glucose
Image Credit: Craig Douglas, Michigan State University
Have students think about cellular respiration at an atomic-molecular scale.
Use the slides in the PPT to have the students discuss what is happening during cellular respiration before the molecular modeling activity.
Use Slide 4 to teach students that plants use food in two ways: materials for growth (biosynthesis), and energy (cellular respiration). This is shown at the atomic/molecular scale. Note that cellular respiration occurs in all cells.
Show students slide 5 to have them think about where atoms are moving from and moving to during cellular respiration.
Show slide 6 to explain that atoms and molecules are moving so that plants can get energy through cellular respiration: Plants need glucose and oxygen as reactants, and they must get rid of carbon dioxide and water as waste.
Show slide 7 to explain a somewhat simplified version of movement of all these materials through the potato plant.
Show slide 8 to zoom into a stem cell in the potato plant to illustrate cellular respiration at the cellular scale. Glucose and oxygen enter the cell; carbon dioxide and water leave—and cell gets energy to function!
Have them look at the Potato 11 x 17 Poster to discuss the parts of a potato plant involved in cellular respiration on a macroscopic scale. Tell students that all parts (all cells) of a potato plant undergo cellular respiration.

7. How do atoms move when a stem cell gets energy from glucose
water
carbon dioxide
oxygen
glucose
Image Credit: Craig Douglas, Michigan State University
Have students think about cellular respiration at an atomic-molecular scale.
Use the slides in the PPT to have the students discuss what is happening during cellular respiration before the molecular modeling activity.
Use Slide 4 to teach students that plants use food in two ways: materials for growth (biosynthesis), and energy (cellular respiration). This is shown at the atomic/molecular scale. Note that cellular respiration occurs in all cells.
Show students slide 5 to have them think about where atoms are moving from and moving to during cellular respiration.
Show slide 6 to explain that atoms and molecules are moving so that plants can get energy through cellular respiration: Plants need glucose and oxygen as reactants, and they must get rid of carbon dioxide and water as waste.
Show slide 7 to explain a somewhat simplified version of movement of all these materials through the potato plant.
Show slide 8 to zoom into a stem cell in the potato plant to illustrate cellular respiration at the cellular scale. Glucose and oxygen enter the cell; carbon dioxide and water leave—and cell gets energy to function!
Have them look at the Potato 11 x 17 Poster to discuss the parts of a potato plant involved in cellular respiration on a macroscopic scale. Tell students that all parts (all cells) of a potato plant undergo cellular respiration.

8. What happens inside the stem cell during cellular respiration?
Chemical change
Image Credit: Craig Douglas, Michigan State University
Have students think about cellular respiration at an atomic-molecular scale.
Use the slides in the PPT to have the students discuss what is happening during cellular respiration before the molecular modeling activity.
Use Slide 4 to teach students that plants use food in two ways: materials for growth (biosynthesis), and energy (cellular respiration). This is shown at the atomic/molecular scale. Note that cellular respiration occurs in all cells.
Show students slide 5 to have them think about where atoms are moving from and moving to during cellular respiration.
Show slide 6 to explain that atoms and molecules are moving so that plants can get energy through cellular respiration: Plants need glucose and oxygen as reactants, and they must get rid of carbon dioxide and water as waste.
Show slide 7 to explain a somewhat simplified version of movement of all these materials through the potato plant.
Show slide 8 to zoom into a stem cell in the potato plant to illustrate cellular respiration at the cellular scale. Glucose and oxygen enter the cell; carbon dioxide and water leave—and cell gets energy to function!
Have them look at the Potato 11 x 17 Poster to discuss the parts of a potato plant involved in cellular respiration on a macroscopic scale. Tell students that all parts (all cells) of a potato plant undergo cellular respiration.

9. How atoms bond together in molecules
Atoms in stable molecules always have a certain number of bonds to other atoms:
Carbon: 4 bonds
Oxygen: 2 bonds
Hydrogen: 1 bond
Oxygen atoms do NOT bond to other oxygen atoms if they can bond to carbon or hydrogen instead.
Chemical energy is stored in bonds between atoms
Some bonds (C-C and C-H) have high chemical energy
Other bonds (C-O and O-H) have low chemical energy
(Optional) Have students use the molecular model kits to construct the reactants.
If students already used the models to demonstrate cellular respiration in the Animals Unit or Decomposers Unit, and if they performed well on the pretest for questions about cellular respiration, you may decide to skip this step. However, we recommend that students use the molecular models here to reinforce the idea that plants also perform cellular respiration.
If you choose to use the models, divide students into pairs and give each pair a molecular model kit, a set of Forms of Energy Cards, and Molecular Models 11 x 17 Placemat. Pass out one copy of 3.3 Molecular Models for Potato Cellular Respiration Worksheet to each student.
Show students slide 9 to explain the bonding of atoms in molecules. Tell students that the rules on this slide are important because they apply to all molecules that they will make in all Carbon TIME units.
Use slide 10 to show instructions to construct the reactants: sugar and oxygen. Students can also follow instructions in Part B of their worksheet.
Use slide 11 to instruct students to compare their own molecule with the picture on the slide.
Slide 12 shows an important message: after students create their reactant molecules, make sure they put away all unused pieces of their molecule kits. This helps reinforce that the matter and energy in the reactants are conserved through the chemical change, and that only the materials from the reactants are used to build the products.

10. Making the reactant molecules: sugar and oxygen
Cellular respiration occurs when sugar (C6H12O6) reacts with oxygen (O2). Make a molecules of sugar and oxygen on the reactant side of your Molecular Models poster:
Get the atoms you will need to make your molecules. Can you figure out from the formula for sugar how many C, H, and O atoms you will need?
Use the bonds to make models of a sugar molecule (C6H12O6) and at least 6 oxygen molecules (O2, with a double bond)
Identify the high-energy bonds (C-C and C-H) by putting twisty ties on them. How many high energy bonds does a molecule of sugar have?
Compare your molecules to the pictures on the next slide. Are they the same?
(Optional) Have students use the molecular model kits to construct the reactants.
If students already used the models to demonstrate cellular respiration in the Animals Unit or Decomposers Unit, and if they performed well on the pretest for questions about cellular respiration, you may decide to skip this step. However, we recommend that students use the molecular models here to reinforce the idea that plants also perform cellular respiration.
If you choose to use the models, divide students into pairs and give each pair a molecular model kit, a set of Forms of Energy Cards, and Molecular Models 11 x 17 Placemat. Pass out one copy of 3.3 Molecular Models for Potato Cellular Respiration Worksheet to each student.
Show students slide 9 to explain the bonding of atoms in molecules. Tell students that the rules on this slide are important because they apply to all molecules that they will make in all Carbon TIME units.
Use slide 10 to show instructions to construct the reactants: sugar and oxygen. Students can also follow instructions in Part B of their worksheet.
Use slide 11 to instruct students to compare their own molecule with the picture on the slide.
Slide 12 shows an important message: after students create their reactant molecules, make sure they put away all unused pieces of their molecule kits. This helps reinforce that the matter and energy in the reactants are conserved through the chemical change, and that only the materials from the reactants are used to build the products.

11. Photo of reactant molecules: H6C12O6 (sugar) and O2 (oxygen) Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products.
Glucose
Chemical change
Oxygen
Image Credit (energy cards): Craig Douglas, Michigan State University
Image Credit (molecules): Michigan State University
(Optional) Have students use the molecular model kits to construct the reactants.
If students already used the models to demonstrate cellular respiration in the Animals Unit or Decomposers Unit, and if they performed well on the pretest for questions about cellular respiration, you may decide to skip this step. However, we recommend that students use the molecular models here to reinforce the idea that plants also perform cellular respiration.
If you choose to use the models, divide students into pairs and give each pair a molecular model kit, a set of Forms of Energy Cards, and Molecular Models 11 x 17 Placemat. Pass out one copy of 3.3 Molecular Models for Potato Cellular Respiration Worksheet to each student.
Show students slide 9 to explain the bonding of atoms in molecules. Tell students that the rules on this slide are important because they apply to all molecules that they will make in all Carbon TIME units.
Use slide 10 to show instructions to construct the reactants: sugar and oxygen. Students can also follow instructions in Part B of their worksheet.
Use slide 11 to instruct students to compare their own molecule with the picture on the slide.
Slide 12 shows an important message: after students create their reactant molecules, make sure they put away all unused pieces of their molecule kits. This helps reinforce that the matter and energy in the reactants are conserved through the chemical change, and that only the materials from the reactants are used to build the products.
Have students read Slide 8 along with instructions in Part A of their worksheets to assist them with making the reactant molecules. Have students place their glucose and oxygen molecules on the reactants side of the poster.
Tell students to place the chemical energy card underneath the glucose molecule, because this is where the chemical energy is stored.
Reactants
Products
Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away).

12. Important:
When you are finished constructing the reactants, put all extra pieces away.
(Optional) Have students use the molecular model kits to construct the reactants.
If students already used the models to demonstrate cellular respiration in the Animals Unit or Decomposers Unit, and if they performed well on the pretest for questions about cellular respiration, you may decide to skip this step. However, we recommend that students use the molecular models here to reinforce the idea that plants also perform cellular respiration.
If you choose to use the models, divide students into pairs and give each pair a molecular model kit, a set of Forms of Energy Cards, and Molecular Models 11 x 17 Placemat. Pass out one copy of 3.3 Molecular Models for Potato Cellular Respiration Worksheet to each student.
Show students slide 9 to explain the bonding of atoms in molecules. Tell students that the rules on this slide are important because they apply to all molecules that they will make in all Carbon TIME units.
Use slide 10 to show instructions to construct the reactants: sugar and oxygen. Students can also follow instructions in Part B of their worksheet.
Use slide 11 to instruct students to compare their own molecule with the picture on the slide.
Slide 12 shows an important message: after students create their reactant molecules, make sure they put away all unused pieces of their molecule kits. This helps reinforce that the matter and energy in the reactants are conserved through the chemical change, and that only the materials from the reactants are used to build the products.

13. Rearranging the Atoms to Make Product Molecules: Carbon Dioxide and Water
Cellular respiration occurs when sugar (C6H12O6) reacts with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O). Show how this can happen:
The reaction breaks the bonds in the molecules, so their bonds can break. Now they can recombine into carbon dioxide (CO2) and water vapor (H2O). Make as many of these molecules as you can from one sugar molecule.
Figure out numbers of molecules:
How many O2 molecules do you need to combine with one sugar molecule?
How many CO2 and H2O molecules are produced by respiring one molecule?
Remember, atoms last forever. So you can make and break bonds, but you still need the same atoms.
Remember, energy lasts forever. What forms of energy do the twisty ties represent now?
Compare your molecules to the pictures on the next slide. Are they the same?
(Optional) Have students construct a model of the chemical change.
Tell students to follow the instructions on the worksheet to construct their products.
Show slide 13 of the PPT and have students re-arrange the atoms to make molecules of CO2 and H2O. To do this, they will need to move their molecules from the reactants side to the products side of the placemat. Explain to students that atoms last forever, so they should not add or subtract atoms when they change the reactant molecule into product molecules.
Show students Slide 14 to compare the products to theirs.
Show students Slide 15 to compare the molecules they made to the molecules on the slide.

14. Photo of product molecules: CO2 (carbon dioxide) and H2O (water) Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products.
Chemical change
Carbon dioxide
Water
Image Credit (energy cards): Craig Douglas, Michigan State University
Image Credit (molecules): Michigan State University
(Optional) Have students construct a model of the chemical change.
Tell students to follow the instructions on the worksheet to construct their products.
Show slide 13 of the PPT and have students re-arrange the atoms to make molecules of CO2 and H2O. To do this, they will need to move their molecules from the reactants side to the products side of the placemat. Explain to students that atoms last forever, so they should not add or subtract atoms when they change the reactant molecule into product molecules.
Show students Slide 14 to compare the products to theirs.
Show students Slide 15 to compare the molecules they made to the molecules on the slide.
Show Slide 10 to let students compare their products to the products in the picture. Have students use new energy cards (heat and motion) to indicate what form the energy is in after the chemical change by putting the card under the twist ties.
Reactants
Products
Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away).

15. Comparing photos of reactant and product molecules
Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products.
Glucose
Chemical change
Carbon dioxide
Water
Oxygen
Image Credit (energy cards): Craig Douglas, Michigan State University
Image Credit (molecules): Michigan State University
(Optional) Have students construct a model of the chemical change.
Tell students to follow the instructions on the worksheet to construct their products.
Show slide 13 of the PPT and have students re-arrange the atoms to make molecules of CO2 and H2O. To do this, they will need to move their molecules from the reactants side to the products side of the placemat. Explain to students that atoms last forever, so they should not add or subtract atoms when they change the reactant molecule into product molecules.
Show students Slide 14 to compare the products to theirs.
Show students Slide 15 to compare the molecules they made to the molecules on the slide.
Show Slide 11 to give students an overview of the entire reaction.
Reactants
Products
Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away).

16. What happens to atoms and energy in cellular respiration?
Carbon Dioxide
Glucose
Reactants
Chemical change
Image Credit: Craig Douglas, Michigan State University
(Optional) Have students watch an animation of the chemical change.
Show slides in the PPT to help students make connections between what is happening in the animation and the molecular models they made.
For each slide, focus on different atoms and forms of energy and how they change. The animation draws attention to where they atoms begin and end in the reaction.
Water
Products
Oxygen
Heat and motion energy

17. What happens to carbon atoms in cellular respiration?
Carbon Dioxide
Glucose
Reactants
Chemical change
Image Credit: Craig Douglas, Michigan State University
(Optional) Have students watch an animation of the chemical change.
Show slides in the PPT to help students make connections between what is happening in the animation and the molecular models they made.
For each slide, focus on different atoms and forms of energy and how they change. The animation draws attention to where they atoms begin and end in the reaction.
Water
Products
Carbon atoms become part of carbon dioxide molecules.
Oxygen
Heat and motion energy 17

18. What happens to oxygen and hydrogen atoms during cellular respiration?
Carbon Dioxide
Glucose
Reactants
Chemical change
Image Credit: Craig Douglas, Michigan State University
(Optional) Have students watch an animation of the chemical change.
Show slides in the PPT to help students make connections between what is happening in the animation and the molecular models they made.
For each slide, focus on different atoms and forms of energy and how they change. The animation draws attention to where they atoms begin and end in the reaction.
Water
Products
Oxygen and hydrogen atoms become part of carbon dioxide and water molecules.
Oxygen
Motion and heat energy

19. What happens to chemical energy in cellular respiration?
Carbon Dioxide
Glucose
Reactants
Chemical change
Image Credit: Craig Douglas, Michigan State University
(Optional) Have students watch an animation of the chemical change.
Show slides in the PPT to help students make connections between what is happening in the animation and the molecular models they made.
For each slide, focus on different atoms and forms of energy and how they change. The animation draws attention to where they atoms begin and end in the reaction.
Water
Products
Chemical energy is transformed into heat and motion energy.
Oxygen
Heat and motion energy

20. What happens to atoms and energy in cellular respiration?
Carbon Dioxide
Glucose
Reactants
Chemical change
Image Credit: Craig Douglas, Michigan State University
(Optional) Have students watch an animation of the chemical change.
Show slides in the PPT to help students make connections between what is happening in the animation and the molecular models they made.
For each slide, focus on different atoms and forms of energy and how they change. The animation draws attention to where they atoms begin and end in the reaction.
Water
Products
Atoms last forever! Energy lasts forever!
Oxygen
Heat and motion energy

21. Writing a chemical equation
Chemists use chemical equations to show how atoms of reactant molecules are rearranged to make product molecules
Writing the equation in symbols: Chemists use an arrow to show how reactants change into products: [reactant molecule formulas] product molecule formulas]
Saying it in words: Chemists read the arrow as “yield” or “yields:” [reactant molecule names] yield [product molecule names]
Equations must be balanced: Atoms last forever, so reactant and product molecules must have the same number of each kind of atom
Try it: can you write a balanced chemical equation to show the chemical change when animals move (use energy)?
(Optional) Help students write a balanced chemical equation.
Tell students that now that they have represented a chemical equation using molecular models and in animations, they will represent chemical change by writing the chemical equation.
Show Slide 21 of the presentation to guide students through the process of writing a balanced chemical equation for cellular respiration. Tell students that these rules apply to all chemical reactions.
Tell students to write their equations in Part C of their worksheet.
Have students write their own chemical equations before comparing them with the one on Slide 22.

22. Chemical equation for cellular respiration
C6H12O6 + 6O2  6 CO2 + 6 H2O
(in words: sugar reacts with oxygen to yield carbon dioxide and water)
(Optional) Help students write a balanced chemical equation.
Tell students that now that they have represented a chemical equation using molecular models and in animations, they will represent chemical change by writing the chemical equation.
Show Slide 21 of the presentation to guide students through the process of writing a balanced chemical equation for cellular respiration. Tell students that these rules apply to all chemical reactions.
Tell students to write their equations in Part C of their worksheet.
Have students write their own chemical equations before comparing them with the one on Slide 22.

23. Have students connect the atomic-molecular level to the macroscopic level.
Use the image on slide 23 and have students practice describing what happens during cellular respiration at a macroscopic level.
Ask: What new information do we have about how plants get energy to move?