Carbon: Transformations in Matter and Energy Environmental Literacy Project Michigan State University Animals Unit Activity 4.3 Molecular Models for Cow Cellular Respiration

Animals use food in two ways 2 FoodDigestion Materials for growth: Biosynthesis Energy: Cellular respiration

How do oxygen and food help a cow use energy to move?

Where are atoms moving from? Where are atoms moving to? The Movement Question

Which atoms and molecules move during cellular respiration? water carbon dioxideoxygen glucose

water carbon dioxideoxygen glucose How do glucose, oxygen, water, and carbon dioxide move through the cow?

What happens inside a muscle cell during cellular respiration? Chemical change

How Atoms Bond Together in Molecules Atoms in stable molecules always have a certain number of bonds to other atoms: – Carbon: 4 bonds – Oxygen: 2 bonds – Hydrogen: 1 bond Oxygen atoms do NOT bond to other oxygen atoms if they can bond to carbon or hydrogen instead. Chemical energy is stored in bonds between atoms – Some bonds (C-C and C-H) have high chemical energy – Other bonds (C-O and O-H) have low chemical energy

Making the Reactant Molecules: Sugar and Oxygen Cellular respiration occurs when sugar (C 6 H 12 O 6 ) reacts with oxygen (O 2 ). Make a molecule of sugar and oxygen on the reactant side of your Molecular Models Placemat: 1.Get the atoms you will need to make your molecules. Can you figure out from the formula for sugar how many C, H, and O atoms you will need? 2.Use the bonds to make models of a sugar molecule (C 6 H 12 O 6 ) and at least 6 oxygen molecules (O 2, with a double bond) 3.Identify the high-energy bonds (C-C and C-H) by putting twist ties on them. How many high energy bonds does a molecule of sugar have? 4.Compare your molecules to the pictures on the next slide. Are they the same?

10 Photo of reactant molecules: H 6 C 12 O 6 (sugar) and O 2 (oxygen) Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products. Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away). Chemical change Reactants Products Glucose Oxygen

Important: When you are finished constructing the reactants, put all extra pieces away. 11

Rearranging the Atoms to Make Product Molecules: Carbon Dioxide and Water Cellular respiration occurs when sugar (C 6 H 12 O 6 ) reacts with oxygen (O 2 ) to produce carbon dioxide (CO 2 ) and water (H 2 O). Show how this can happen: 1.The reaction breaks the bonds in the molecules, so their bonds can break. Now they can recombine into carbon dioxide (CO 2 ) and water vapor (H 2 O). Make as many of these molecules as you can from one sugar molecule. 2.Figure out numbers of molecules: a)How many O 2 molecules do you need to combine with one sugar molecule? b)How many CO 2 and H 2 O molecules are produced by respiring one molecule? 3.Remember, atoms last forever. So you can make and break bonds, but you still need the same atoms. 4.Remember, energy lasts forever. What forms of energy do the twist ties represent now? 5.Compare your molecules to the pictures on the next slide. Are they the same?

13 Photo of product molecules: CO 2 (carbon dioxide) and H 2 O (water) Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products. Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away). Chemical change Reactants Products Water Carbon dioxide

14 Comparing photos of reactant and product molecules Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products. Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away). Chemical change Reactants Products Water Carbon dioxide Glucose Oxygen

Reactants Products Chemical change Glucose Oxygen Water Motion and heat energy Carbon Dioxide 15 What happens to atoms and energy in cellular respiration?

Reactants Products Chemical change Glucose Oxygen Water Motion and heat energy Carbon Dioxide What happens to carbon atoms and chemical energy in cellular respiration? 16 Carbon atoms become part of carbon dioxide molecules and Chemical energy is transformed into energy for cell work and heat energy.

Reactants Products Chemical change Glucose Oxygen Water Carbon Dioxide 17 What happens to atoms and energy during cellular respiration? Motion and heat energy

Reactants Products Chemical change Glucose Oxygen Water Carbon Dioxide Carbon atoms become part of carbon dioxide molecules. 18 What happens to carbon atoms during cellular respiration? Motion and heat energy

Reactants Products Chemical change Glucose Oxygen Water Carbon Dioxide Oxygen and hydrogen atoms become part of carbon dioxide and water molecules. 19 What happens to oxygen and hydrogen atoms during cellular respiration? Motion and heat energy

Reactants Products Chemical change Glucose Oxygen Water Carbon Dioxide 20 What happens to chemical energy during cellular respiration? Motion and heat energy Chemical energy is transformed into energy for cell work and heat energy.

Reactants Products Chemical change Glucose Oxygen Water Carbon Dioxide 21 What happens to atoms and energy during cellular respiration? Motion and heat energy Atoms last forever! Energy lasts forever!

Writing a Chemical Equation Chemists use chemical equations to show how atoms of reactant molecules are rearranged to make product molecules Writing the equation in symbols: Chemists use an arrow to show how reactants change into products: [reactant molecule formulas]  product molecule formulas] Saying it in words: Chemists read the arrow as “yield” or “yields:” [reactant molecule names] yield [product molecule names] Equations must be balanced: Atoms last forever, so reactant and product molecules must have the same number of each kind of atom Try it: can you write a balanced chemical equation to show the chemical change when animals move (use energy)?

23 Chemical equation for cellular respiration C 6 H 12 O 6 + 6O 2  6 CO H 2 O (in words: sugar reacts with oxygen to yield carbon dioxide and water)