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Plants | Activity 4.1

Activity 4.1: Molecular Models for Potatoes Moving and Functioning: Cellular Respiration (30 min)

Students watch a video of plants moving and begin discussing how this happens. Students then model the oxidation of glucose (CgH12O6) to carbon dioxide and water using molecular model kits. They describe this chemical change in two ways: molecular models, and a chemical equation.

Note that the steps that have students construct molecular models in this activity are optional if students did molecular modeling for cellular respiration in another unit and performed well on the Plants Pretest for items related to cellular respiration.

Materials You Provide

Resources Provided


Prepare one model kit, one Molecular Models 11 x 17 Placemat, one pair of scissors, and one set of the Forms of Energy Cards for each pair of students. Print one copy of the 4.1 Molecular Models for Potato Cellular Respiration Worksheet for each pair of students. Prepare a computer and a projector to display the PPT. Retrieve the materials from Activity 3.5. This may include PPT slides from the lesson in which you typed students’ unanswered questions or a photograph of their unanswered questions.


1. Use the instructional model to show students where they are in the course of the unit.


Listen to students’ ideas about how plants get energy to move. Are they able to make connections to the results from the Plants in the Dark Investigation? Are they able to make connections to their experiences with the molecular modeling of cellular respiration?

If you had students complete the molecular modeling part of this activity, use 4.1 Grading the Molecular Models for Potato Cellular Respiration Worksheet to get a sense of students’ initial ideas and explanations about cellular respiration in plants. Students should be able to follow instructions and complete the worksheet correctly, so it is reasonable to grade this worksheet.


  • You may want to display the results from the investigation from Lesson 3.
  • Have students record their ideas about how plants get energy to move on individual posters.
  • If you choose to do the optional molecular models piece, stress that although we are using twist ties to represent energy, energy is actually not made of matter/molecules!

Extending the Learning

  • Plants do not give off CO2 at night only! Plants perform cellular respiration 24 hours a day. Encourage students to think about why we observed plants giving off CO2 at night only, but we were unable to detect their CO2 during the day.
  • Have students compare the chemical reaction for combustion and the chemical reaction for cellular respiration. Ask: What do you notice about these two reactions? What do they have in common?