1. Carbon: Transformations in Matter and Energy
Environmental Literacy Project Michigan State University
Animals Unit Activity 4.1: Molecular Models for Cows Growing: Digestion and Biosynthesis
Image Credit: Craig Douglas, Michigan State University

2. All animals eat. What happens to the food that they eat?
Image Credit (mealworms): FableVision
Image Credit (cow, baby): Craig Douglas, Michigan State University

3. Animals don’t digest all the food that they eat
Our digestive systems cannot break down some large organic molecules (such as fiber).
These molecules leave our bodies as feces.
Image Credit: Craig Douglas, Michigan State University

4. What are the inputs and outputs of a cow’s body?
Image Credit: Craig Douglas, Michigan State University

5. Matter entering and leaving animals
Materials in a cow
Materials in grass
(entering cow)
minerals
H2O
Carbohydrates
minerals
Protein
Protein
H2O
Fat
Fat
Protein
H2O
CO2
minerals
Image Credit (grass): Hannah Miller, Michigan State University
Image Credit (cow): Craig Douglas, Michigan State University
H2O
Carbohydrates
minerals
From lungs
Materials leave a
cow by breathing,
urination and perspiration.
feces

6. How does a cow get food to a cell in its leg?
Image Credit (cows): Craig Douglas, Michigan State University
What is food made of?
What are animals made of?
How can cows get food to a cell in its leg?
How can cows use this food to build their bodies?

7. Food is mostly water and large organic molecules
CARBOHYDRATES:
STARCH
LIPIDS (FAT)
Image Credit (molecules): Craig Douglas, Michigan State University
GLUCOSE (SUGAR)
PROTEINS
CELLULOSE (FIBER)

8. Animals are mostly water and different large organic molecules
How can animals make these molecules from molecules in the food they eat?
LIPIDS (FAT)
Image Credit: Craig Douglas, Michigan State University
PROTEINS

9. Food molecules are in the grass
Image Credit: Craig Douglas, Michigan State University
Place penny here: large food molecules (grass).

10. Step 1: Digestion Materials for growth: Biosynthesis Food Digestion
Energy: Cellular respiration
Image Credit: Craig Douglas, Michigan State University

11. in stomach and small intestines
Digestion occurs
in stomach and small intestines
Put penny here: Large food molecules break into small molecules in intestines
Image Credit: Craig Douglas, Michigan State University

12. During digestion, large organic molecules are broken down into small organic molecules
LARGE = Polymer
SMALL = Monomers
Image Credit: Craig Douglas, Michigan State University
STARCH
GLUCOSE (SUGAR)

13. What happens to food that animals can’t digest?
Our digestive systems cannot break down some large organic molecules (such as fiber).
These molecules leave our bodies as feces.
Image Credit: Craig Douglas, Michigan State University

14. 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
Image Credit: Craig Douglas, Michigan State University

15. Breakdown Protein Molecules (Digestion)
Let’s focus on what happens to PROTEIN in food.
(Put the other food molecules to the side for now.)
Digest PROTEIN molecules by cutting the protein into individual amino acids.
Notice that after you cut the protein apart there are bonds without atoms. Cut up water molecules to tape an –H and –OH to every amino acid.
Image Credit: Craig Douglas, Michigan State University
Chemical change

16. What happens to carbon atoms and chemical energy in digestion?
Chemical change
Image Credit: Craig Douglas, Michigan State University
Protein polymer (+ water)
Amino acid monomers
Reactants
Products

17. What happens to carbon atoms and chemical energy in digestion?
Chemical change
Image Credit: Craig Douglas, Michigan State University
Carbon atoms stay in organic molecules with high-energy bonds
Protein polymer (+ water)
Amino acid monomers
Reactants
Products

18. Breakdown of Starch Molecules (Digestion)
Digest STARCH molecules by cutting the starch into individual glucose monomers.
Notice that after you cut the starch apart there are bonds without atoms. Cut up water molecules to tape an –H and –OH to every glucose.
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University

19. What happens to carbon atoms and chemical energy in digestion?
Chemical change
Image Credit: Craig Douglas, Michigan State University
Starch polymer (+ water)
Glucose monomers
Reactants
Products

20. What happens to carbon atoms and chemical energy in digestion?
Chemical change
Image Credit: Craig Douglas, Michigan State University
Carbon atoms stay in organic molecules with high-energy bonds
Starch polymer (+ water)
Glucose monomers
Reactants
Products 20

21. Breakdown of Fat Molecules (Digestion)
Digest FAT molecules by breaking the fat into individual fatty acid and glycerol monomers.
Notice that after you cut the fat apart there are bonds without atoms. Cut up water molecules to tape an –H and –OH to each fatty acid and glycerol.
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University

22. What happens to carbon atoms and chemical energy in digestion?
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University
Fat (+ water)
Fatty acids
+ glycerol
Reactants
Products

23. What happens to carbon atoms and chemical energy in digestion?
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University
Carbon atoms stay in organic molecules with high-energy bonds
Fat (+ water)
Fatty acids
+ glycerol
Reactants
Products

24. Where do digested monomers go?
glucose
fatty acid
Image Credit: Craig Douglas, Michigan State University
glycerol
amino acid

25. Blood carries digested monomers to all parts of animal bodies.
Image Credit: Craig Douglas, Michigan State University

26. Step 2: Biosynthesis Materials for growth: Biosynthesis Food Digestion
Energy: Cellular respiration
Image Credit: Craig Douglas, Michigan State University

27. Move Markers: Small molecules move through circulatory system
Small molecules move from intestines to blood, and the heart pumps blood and small molecules to all parts of the body.
Image Credit: Craig Douglas, Michigan State University
Move Markers: Small molecules move through circulatory system

28. Place your marker here: Large molecules are built here
Biosynthesis is the process of small organic molecules becoming large organic molecules in all body parts
Place your marker here: Large molecules are built here
Image Credit: Craig Douglas, Michigan State University

29. What’s in cow muscles (BEEF)?
PROTEIN FAT
Image Credit (molecule): Craig Douglas, Michigan State University

30. Build Cow Muscles (Biosynthesis)
Build PROTEIN molecules by taping 4 amino acid monomers together.
Notice you will need to remove an –H and –OH from each amino acid. Tape these back together to make water.
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University

31. What happens to carbon atoms and chemical energy in biosynthesis?
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University
Amino acid monomers
Protein polymer (+ water)
Reactants
Products

32. What happens to carbon atoms and chemical energy in biosynthesis?
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University
Carbon atoms stay in organic molecules with high-energy bonds
Amino acid monomers
Protein polymer (+ water)
Reactants
Products

33. Build Cow Muscles (Biosynthesis)
Build FAT molecules by taping 3 fatty acid monomers to 1 glycerol molecule.
Notice you will need to remove an –H and –OH from each fatty acid and glycerol. Tape these back together to make water.
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University

34. What happens to carbon atoms and chemical energy in biosynthesis?
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University
Fatty acids + glycerol
Fat (+ water)
Reactants
Products

35. What happens to carbon atoms and chemical energy in biosynthesis?
Chemical change
Image Credit (molecule): Craig Douglas, Michigan State University
Carbon atoms stay in organic molecules with high-energy bonds
Fatty acids + glycerol
Fat (+ water)
Reactants
Products

36. How do animal cells use sugar?
The diets of most animals—including mealworms, cows, and humans—include lots of carbohydrates (starch, fiber, sugar)
This means that lots of sugar travels to animal cells in the blood.
BUT animal cells don’t make starch or cellulose.
How do they use the sugar?

37. Animal cells use sugar in two ways
Animal cells can make fat molecules from sugar molecules.
Glycerol and fatty acids are made of the same atoms—C, H, and O—as sugar molecules
Animals use fats to store chemical energy in C-C and C-H bonds
Animal cells can combine sugar molecules with oxygen to release chemical energy.
This is how all cells get the energy they need for their functions.

38. Coming up: How Animals Use Food for Energy
Materials for growth: Biosynthesis
Food
Digestion
Energy: Cellular respiration
Image Credit: Craig Douglas, Michigan State University