Polymers: Small Changes Lead to Big Function
Purpose: This lesson is intended to introduce students to the basics of polymer chemistry in very general
terms. Parts of this lesson are intended to link the basics of molecular chemistry to genetics, but the
overall theme is that form influences function and how the world is based on polymers. This lesson can
link into another one (a second part) but can also stand on its own.
Overview: In this activity students will start to work with small units (paperclips or LEGOs) and build
larger shapes. This leads into a discussion about how form determines function, and then how small
pieces can add up to large molecules.
Student Outcomes: Students will be able to recognize polymers in their environment when asked, as
well as how they are used in their everyday lives. Students will also be able to realize how similar small
molecules can add up to large changes when placed together differently. Students will begin to
understand how the shape of molecules they have studied can impact function.
Illinois State Standards:
11.A.3e Use representational methods to analyze scientific data.
(Link to genetics section) 12.A.3a Explain how cells function as “building blocks” of organisms and
describe the requirements for cells to live.
12.C.3b Model and describe the chemical and physical characteristics of matter
13.B.3a Identify and explain ways that scientific knowledge and economics drive technological
development.
13.B.3b Identify important contributions to science and technology that have been made by individuals
and groups from various cultures.
13.B.3c Describe how occupations use scientific and technological knowledge and skills.
Time: This lesson is intended for one 45 minute class period.
Level: This lesson is intended for 8th grade students.
Materials and Tools
The activity starts with paperclips or Legos, enough for at least the teacher to demonstrate but
preferably for each small group of students to use themselves. A presentation with examples of
polymers in both unit forms and the resulting large forms.
Suggested resources: Teachers should be familiar with polymers and examples thereof for
student questions.
Preparation:
Setup: The PowerPoint should be loaded and small bags of either Legos or paperclips should be available
for easy handout and collection (so the students don’t keep playing when they should be listening).
Prerequisites: This lesson is intended for students who are just finishing up two trimesters about
chemistry and physical interactions, then moving into genetics. Students should be familiar with
molecular interactions and how molecules are drawn, as well as basic intermolecular forces and
bonding.
Background:
Periodic trends, types of atoms, some knowledge of types of molecules helpful, covered types of bond
and molecular interactions, what a cell looks like and what might be inside (from long ago) for the part
to bridge into genetics.
Review: Types of Bonds and Interactions
Covalent: Strong bond sharing electrons where the electronegativity difference between the two is small
Ionic: Attractive bond between two ions of opposite charge.
Dipole-dipole: An interaction between molecules where opposite polarities keep the atoms close
together
Dispersion (London) forces: General interactions between atoms and molecules due to instantaneous
dipoles forming because electron cloud is not uniform around the atom.
Hydrogen Bonding: a very strong dipole-dipole bond resulting from electronegativity differences
between Hydrogen and Oxygen, Fluorine, Chlorine, etc.
Teaching Notes:
Polymers:
Poly: Many, Meros: part One large molecule made up of many smaller parts pieced together
(Paper clip example) They are everywhere! You have all heard the saying “the whole is greater than the
sum of its parts”, well that’s very true for polymers. One part may have certain properties, but when
linked together they could have something completely different.
For example, Glucose is a small sugar molecule. This molecule is
very water soluble, it tastes sweet to us, our bodies can use it for
fuel very easily.
However, when these glucose molecules are linked together, the
result can be cellulose—a starch. Cellulose doesn’t taste at all like
sugar, and it is the molecule that allows plants to grow strong and
tough.
Plants don’t dissolve when it rains because
cellulose isn’t soluble in water unlike glucose.
You can link polymers in long chains, but you can also branch them off in different ways. When you have
something branched, obviously it can’t fit together as easily, so it becomes something completely
different. If you remember that cellulose example from before, how the long chains allow the plan to
grow strong and tall, what do you think would happen if there are lots of branches stopping the
cellulose from stacking side by side neatly? (Picture left)
This is glycogen. When we have too much glucose in our
body, this is how our body stores it. It’s still the same
small units, but the way it’s put together makes it have
very different properties. We can’t break down starch on
our own, but our cells can use the glucose if it’s put
together this way, so we can save it for when we need
fuel quickly.
Polymers are everywhere around you. Some people
make them in a lab, and many of those are called
“plastics”, but nature has been using polymers far longer
than we have been making them. Without them, we
couldn’t be standing where we are today because every
part of our body is made up of
polymers.
Let’s take a look at a cell.
Everyone remembers what a
human cell looks like right? (have
someone draw an example).
There are lots of parts in a cell,
and everything is usually very organized. But what makes up all of this? Polymers! Let’s look at just a
few of the types of polymers (and if you want to think about it, polymers can go into other polymers to
make up even longer chains!). We already mentioned carbohydrates earlier—ones that are made up of
sugars. Those are usually on the outsides of cells but they aren’t always. Let’s think about other types.
You can have polymers made of lipids (fats) that make up the plasma membrane and a lot of other
membranes. Because they repel the water around them they can keep things that aren’t hydrophilic
safe.
Proteins are one of the biggest classes of polymers in you. They’re made up of 20 amino acids (the
“parts”) that are then strung together like a paper clip chain. But after they’re folded because the 20
amino acids have different parts sticking off called “side chains” they get helped along to fold in certain
patterns. So the job isn’t done until they’re folded and can go off to do the work. Sometimes more than
one protein has to come together to get a job done, and we call that a complex.
The last big class of polymers is DNA. Who remembers what that stands for? DNA is a mix of different
molecules all sticking along the deoxyribose backbone, with 4 bases (a different one in RNA) that switch
out. Who can tell me what DNA’s role is in the cell? Does anyone remember? Those bases on the
polymer form codons, which are like letters to your cells. They tell the cell what amino acid to put
where, to build the right type of protein polymer for the job. To continue with the analogy, the letters
are put together to form words, which are then folded into a paper airplane and passed along to where
the message can do its job. We’re going to soon get into lots of details with genetics, but remember the
rules you learned about bonding and interactions don’t go away because we’re switching units—they’re
all still there and have a big role to play! They determine the ultimate shape of the molecule, and shape
determines function!
Assessment: The next day the students will be asked some questions about polymers and what it means
for something to be a polymer. Each class will also be asked to come up with a list of polymers they can
think of and where they are used. Students will also be asked verbally about how different molecules
made of the same thing can have so many different properties.
Additional information: In the first attempt with this lesson this feeds into an exercise in small groups
with the simulation FoldIt. Student involvement can also be assessed with this as well.