Name ______Teacher ______Date ______

Lesson 3.3 Cellular Respiration in Decomposers Worksheet

A. Answering the Movement Question for fungus cells using food for energy.

The Movement Question: Explaining the missing mass. The bread in the bread mold investigation lost mass when fungus grew on it. Where did the missing atoms go? / The Movement Question: Drawing motions of atoms: Draw arrows to show how atoms move into, through, and out of a fungus when its cells are using food as an energy source.

Image Credit: Craig Douglas, Michigan State University

B. Using molecular models to show how decomposers move.

In order for decomposers to move, they need energy. Decomposers get energy from chemical energy either in their food (like carbohydrates), or stored in molecules (like fats) in their bodies. Carbohydrates and fats contain chemical energy stored in high-energy bonds: C-C and C-H bonds.

When decomposers use energy from carbohydrates or fats, they use oxygen (O2) in the air from breathing to produce carbon dioxide (CO2) and water (H2O). Since carbon dioxide and water have only low-energy bonds (C-O and H-O), the chemical energy is released as motion and heat. Use the molecular models to show how this happens.

  1. Work with your partner to make models of the reactant molecules: sugar and oxygen. Sugar is a carbohydrate. Using twist ties, show how chemical energy is stored in the high-energy bonds of sugar.
  2. ☐ Make models of a sugar molecule (C6H12O6) and oxygen molecules (O2, with a double bond). Decomposers use air for cellular respiration, which has lots of oxygen, so make at least 6 O2 molecules. Put these molecules on the reactant side of the Process Tool for Molecular Models 11 x 17 Poster.
  3. ☐ Use twist ties to represent chemical energy. Put a twist tie around each high-energy bond (C-C and C-H bonds) in the sugar molecule. Put the “Chemical Energy” card under the sugar molecule to label the energy in the C-C and C-H bonds. Note how many energy units (twist ties) there are in the sugar molecule.
  4. ☐ Important: place all pieces that were not used to construct the reactants away. You should be able to construct to products with all of the materials in the reactant molecules.
  5. Show how the atoms of the reactant molecules can recombine into product molecules—carbon dioxide and water—and show how chemical energy is released when this happens.
  6. ☐ Take the sugar and some of the oxygen molecules apart and recombine them into carbon dioxide (CO2) and water (H2O) molecules. Put these molecules on the product side of the Process Tool for Molecular Models 11 x 17 Poster. Some things to notice:
  7. How many oxygen molecules reacted with one sugar molecule? _____
  8. How many carbon dioxide molecules were produced? _____
  9. How many water molecules were produced? _____
  10. ☐ Energy lasts forever, so move the twist ties to the product side of the Process Tool for Molecular Models 11 x 17 Poster. Carbon dioxide and water have only low-energy bonds (C-O and H-O), so what forms does the chemical energy change into? Put the correct energy cards under the twist ties.

C. Atoms last forever!! Check yourself: did your number and type of atoms stay the same at the beginning and end of the chemical change? Use the table below to account for all the atoms and bonds in your models.

Energy lasts forever! Write the type of energy for reactants and products in the chemical change.

Matter / Energy
How many
carbon atoms / How many
oxygen atoms / How many
hydrogen atoms / How many twist ties? / What forms of energy?
Began with…
Sugar
Oxygen
Total in reactants
End with…
Carbon Dioxide
Water
Total in products

D. Writing the chemical equation. Use the molecular formulas (C6H12O6, O2, CO2, H2O) and the yield sign (à) to write a balanced chemical equation for the reaction:

______

E. Answering the Three Questions. Use the Process Tool below to answer the Three Questions for fungi USING FOOD FOR ENERGY.

/ Decomposers Unit, Lesson 3, Activity 3
Environmental Literacy Project
Michigan State UniversityXXX