• Build a Sugar ... Then Break it Apart! 
     Modeling Photosynthsis and Respiration with Beads
    1. Get a set of beads with the pipe cleaner frames. Each color represents a different kind of atom. When atoms bond to each other, they form molecules. We are going to use these atoms to make 4 different kinds of molecules.
      Atom-Bead Color Key
    2. In your science notebook, put the title "Breaking Down Glucose (Cellular Respiration)." Then write  a summary of the overall process: "6 oxygen molecules break down 1 glucose molecule into water and carbon dioxide."

    3. Build a glucose molecule. Find the molecule frame (made of pipe cleaners) that has 6 branches. Look at the pattern below to help you assemble the glucose.
      Glucose Molecule Bead Model C6H12O6

    4. Check your work. If you built the molecule correctly, you should have 6 Carbon atoms, 6 oxygen atoms, and 12 hydrogen atoms on your molecule. If not, fix it. (That took a lot of energy, didn't it! Plants use sunlight to get the energy to make glucose. What happens to that energy? It's stored in the molecule!)

    5. Take a deep breath. You know you get oxygen when you breathe, but why? It's because oxygen molecules do the job of taking apart glucose molecules. Your brain cells need energy all the time, which means they have to break down glucose all the time. Your muscle cells need to break down a lot of glucose to work. All these cells need oxygen to break down glucose. You will need 6 oxygen molecules to break apart your 1 glucose molecule.  Use 6 of the small pieces of pipe cleaner to make 6 oxygen molecules. Each one should look like this:
      Oxygen Molecule Bead Model O2

    6. Draw and label your glucose molecule in your science notebook. Draw one of the oxygen atoms too. Make a note that there are 6 of them.

    7. Take out the rest of the small pieces of pipe cleaner and seal up the bag. For the next part, you may only use the atoms from the glucose and oxygen molecules, none from the bag!

    8. Now take them all apart. ("What!?" you say. "I just put it together!" Yup, that's right. Plants put glucose together to store energy. The only way to get that energy back out again is to break the molecule apart. So go for it. The oxygen molecules break apart the glucose, and the oxygen molecules come apart too! So take all the atoms apart. (Be sure not to let them fall on the floor or get mixed into your neighbor's stuff. You need each atom!

    9. Reassemble the atoms into water and carbon dioxide molecules.  Most atoms naturally combine with other atoms. They aren't at rest by themselves. The energy released from breaking down the sugar makes ATP, and the atoms don't have enough energy to make another big molecule. Instead they make smaller molecules, which don't require as much energy. In this case, the atoms reassemble into water and carbon dioxide. Reassemble your atoms. Here are the rules:

      1. You can't have any left-overs. Each atom (bead) must be part of a molecule.
      2. The only molecules you can make are carbon dioxide (CO2), and water (H2O).
      3. Use only the atoms from your glucose and oxygen molecules, none from the bag.

    10. How many of each molecule did you end up with? Check with your neighbors, how many did they end up with? If you did it correctly, you should have come up with the same number. If you did, draw the carbon dioxide and water molecules in your notebook. Make a note of how many molecules are produced by this chemical reaction.
      Carbon Dioxide Bead Model CO2                             Water Molecule Bead Model H2O