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
All animals eat.
What happens to the food that they
eat?
2
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.
3
What are the inputs and outputs of a
cow’s body?
4
Matter entering and leaving animals
Materials in grass
(entering cow)
Protein
Fat
Carbohydrates
Materials
in a cow
H2O
H2O
CO2
H2O
From
Materials leave a
lungs
cow by breathing,
urination and perspiration.
H2O
Fat
Protein
feces
5
How does a cow get food to a cell in its
leg?
1.
2.
3.
4.
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?
6
Food is mostly water and large
organic molecules
CARBOHYDRATES:
STARCH
LIPIDS (FAT)
GLUCOSE
(SUGAR)
PROTEINS
CELLULOSE (FIBER)
7
Animals are mostly water and
different large organic molecules
LIPIDS (FAT)
PROTEINS
How can animals make
these molecules from
molecules in the food
they eat?
Food
molecules
are in the
grass
Place penny
here: large
food
molecules
(grass).
9
Step 1: Digestion
Materials
for growth:
Biosynthesis
Food
Digestion
Energy:
Cellular
respiration
10
Digestion occurs
in stomach and small
intestines
Put penny here:
Large food
molecules break
into small
molecules in
intestines
11
During digestion, large organic molecules are
broken down into small organic molecules
LARGE = Polymer
SMALL = Monomers
STARCH
GLUCOSE
(SUGAR)
12
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.
13
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
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.
Chemical
change
15
What happens to carbon
atoms and chemical
energy in digestion?
Chemical change
Protein polymer
(+ water)
Reactants
Amino acid
monomers
Products
16
What happens to carbon
atoms and chemical
energy in digestion?
Chemical change
Protein polymer
(+ water)
Reactants
Carbon atoms stay in
organic molecules with
high-energy bonds
Amino acid
monomers
Products
17
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
18
What happens to carbon
atoms and chemical
energy in digestion?
Chemical change
Starch polymer
(+ water)
Reactants
Glucose monomers
Products
19
What happens to carbon
atoms and chemical
energy in digestion?
Chemical change
Starch polymer
(+ water)
Reactants
Carbon atoms stay in
organic molecules with
high-energy bonds
Glucose monomers
Products
20
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
21
What happens to carbon
atoms and chemical
energy in digestion?
Chemical change
Fat
(+ water)
Reactants
Fatty acids
+ glycerol
Products
22
What happens to carbon
atoms and chemical
energy in digestion?
Chemical change
Fat
(+ water)
Reactants
Carbon atoms stay in
organic molecules with
high-energy bonds
Fatty acids
+ glycerol
Products
23
Where do digested monomers go?
glucose
glycerol
fatty acid
amino acid
24
Blood carries digested monomers
to all parts of animal bodies.
Step 2: Biosynthesis
Materials
for growth:
Biosynthesis
Food
Digestion
Energy:
Cellular
respiration
26
Small molecules move from intestines to blood, and the heart
pumps blood and small molecules to all parts of the body.
Move Markers:
Small molecules
move through
circulatory
system
27
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
28
What’s in cow muscles (BEEF)?
PROTEIN
FAT
29
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
30
What happens to carbon
atoms and chemical
energy in biosynthesis?
Chemical change
Amino acid
monomers
Protein polymer
(+ water)
Reactants
Products
31
What happens to carbon
atoms and chemical
energy in biosynthesis?
Chemical change
Amino acid
monomers
Reactants
Carbon atoms stay in
organic molecules with
high-energy bonds
Protein polymer
(+ water)
Products
32
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
33
What happens to carbon
atoms and chemical
energy in biosynthesis?
Chemical change
Fatty acids
+ glycerol
Fat
(+ water)
Reactants
Products
34
What happens to carbon
atoms and chemical
energy in biosynthesis?
Chemical change
Fatty acids
+ glycerol
Reactants
Carbon atoms stay in
organic molecules with
high-energy bonds
Fat
(+ water)
Products
35
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?
36
Animal cells use sugar in two ways
1. 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
2. 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.
37
Coming up: How Animals Use Food for
Energy
Materials
for growth:
Biosynthesis
Food
Digestion
Energy:
Cellular
respiration
38