Model Photosynthesis and Respiration with Berries

 

Students can model photosynthesis and respiration by making molecules out of strawberries, blueberries, grapes, and toothpicks. I wanted to create a healthier option to the gumdrops that are often used to model molecules, so I experimented with berries, and it worked nicely! 

You can use this activity when teaching Next Generation Science Standard (NGSS) MS-LS1-6: Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy into and out of organisms. It can also be used to teach MS-LS2-3: Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.

Students should prepare for this activity by first creating structural formulas for the reactants and products of photosynthesis and respiration. In a previous class, I provided a handout for students to draw structural formulas of all reactants and products of each process, referring students to this video (start at 6:10 for photosynthesis and 5:33 for respiration):

Chemistry Tutorial: Chemical Equations & Photosynthesis

As students draw their structural formulas, they begin to see that photosynthesis and respiration are opposite processes. 

On the day of the activity, students get directions for creating their berry models. Because carbon atoms are the largest of these atoms, I asked students to represent them using strawberries, the largest berries. The smallest atom, hydrogen, is represented by the smallest berry. Toothpicks are used as bonds.

Strawberries = Carbon Atoms

Grapes = Oxygen Atoms

Blueberries = Hydrogen Atoms

With the structural formulas they created previously in hand, students begin by creating molecules of water and carbon dioxide, the reactants of photosynthesis. You could allow students to work with a partner though you may want students to handle their own berries to prevent the spread of germs. The photo below shows students who successfully completed this first step (one water molecule not shown in the frame).

After building the reactants of photosynthesis, the next step is to model photosynthesis by breaking the bonds in water and carbon dioxide molecules and rearranging the atoms to form glucose, the product of photosynthesis.

The last step is to model respiration by breaking apart the glucose molecule to form the products of respiration, carbon dioxide and water. Students end with the same molecules they started with.

Once students have their hands-on work checked by a teacher and write about the relationship between photosynthesis and respiration, they can eat all the berries. One student told me afterward that she had never really “gotten photosynthesis and respiration” before but understood it now!

If you are interested in another activity that involves playing around with food in the name of science, follow this link to my previous blogpost on making models of cells using pasta and toppings:

Edible Cell Model Made of Pasta

I hope that you enjoyed this blogpost and found it valuable. If you are interested in joining my email list, please follow this link:

                                SUBSCRIBE TO EMAIL LIST