Purpose: To investigate the general processes of photosynthesis and cellular respiration. Part 1: Van Helmont s Experiment Evaluating Past Research

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1 Name: Date: What Does It Take?? (Student sheet 1) Purpose: To investigate the general processes of photosynthesis and cellular respiration. Part 1: Van Helmont s Experiment Evaluating Past Research Jan van Helmont was a 17 th century scientist who attempted to answer the same question posed to you, How does a sapling gain the mass necessary to develop into a full grown tree?. He planted a young tree weighing 5 lbs in 200 lbs of soil. Over five years he added only rain water. After five years, he weighed the tree, including its roots and the soil. These were the results: the tree and roots weighed 169 lbs, the soil weighed 199 lbs 14 oz. 5 lbs 200 lbs 199 lbs 14 ozs 169 lbs Image from: 1. What materials made up the mass of the 169 lbs tree? 2. How would you explain how the tree gained 164 lbs in mass? 3. Discuss and write down possible ways you might test your group s ideas about the source of the additional mass of the tree. 1

2 Part 2: Tracking the matter Illustrating current concepts You will be given a set of molecular models to use in this investigation. Check your materials to make sure that you have six (6) carbon dioxide (CO2) molecules, six (6) water (H2O) molecules, and six (6) extra single bonds. Your models should look like this: Key: Black = Carbon (C) Red = oxygen (O) White = hydrogen (H) Grey = chemical bonds carbon dioxide water (H2O) glucose (C6H12O6) oxygen (O2) (CO2) O=C=O O=O 2

3 A Summary of Photosynthesis 6CO2 + 6H2O light C6H12O6 + 6O2 carbon water 6-carbon oxygen dioxide sugar gas Instructions: (PHOTOSYNTHESIS) 1. Count the number of carbon atoms, oxygen atoms, and hydrogen atoms in the 6 molecules of water and the 6 molecules of carbon dioxide that are the reactants in photosynthesis. Record these numbers below. 2. Now break the bonds in the carbon dioxide and water reactant molecules and construct the sugar and oxygen molecules that are the products of photosynthesis. Count the number of carbon atoms, oxygen atoms, and hydrogen atoms in these product molecules and record below. 3. In an actual cell what happens to these reaction products (sugar and oxygen) after they are made? 3

4 A Summmary of Respiration Enzymes C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + energy glucose oxygen carbon water ATP gas dioxide Instructions: (Cellular Respiration) 1. Look at the sugar molecules and oxygen molecules that are the products of photosynthesis. Compare them to the reactants shown in the equation for cellular respiration. How do they compare in kind and number of molecules? 2. Break the bonds of the reactant molecules (sugar and oxygen) of cellular respiration and construct the product molecules (carbon dioxide and water) of cellular respiration. Count the number of carbon atoms, oxygen atoms, and hydrogen atoms in these molecules and record these numbers below. 3. In living things, what happens to the product molecules of cellular respiration? 4

5 PHOTOSYNTHESIS AND CELLULAR RESIPRATION: COMPLIMENTARY PROCESSES 1. Compare the number of reactant carbon, oxygen, and hydrogen atoms with the number of carbon, oxygen, and hydrogen product atoms in both photosynthesis and cellular respiration. What important law or principle about matter do these comparisons confirm? Explain. 2. Compare the reactants and products of photosynthesis and cellular respiration. Is the matter involved in these two processes recycled? Explain. 3. Why do all organisms, both plants and animals, conduct cellular respiration? 4. In your own words, trace the path of energy from the sun to energy used by your muscles to lift a book. 5. Is the energy involved in photosynthesis and cellular respiration recycled? Explain. Save the carbon dioxide and water molecules that you constructed. Do not tear them apart. Return them to their container. They will be used by the next class. 5