DRAFT, August 2013
Modeling Enzymes & Substrates with Legos in the Cellulosic Biomass to
Ethanol Lab
Note: This activity was developed by Marin Dobson, biology teacher at Fort Atkinson H.S., WI,
while working with GLBRC researchers Shishir Chundawat and Kate Helmich and Education &
Outreach staff as part of the 2013 Research Experience for Teachers Program. This modeling
activity was inspired by the modeling activities developed by the MIT Edgerton Center,
https://edgerton.mit.edu/node/103.
OVERVIEW:
This modeling activity can be used in conjunction with the GLBRC Cellulosic
Biomass to Ethanol (CB2E) Lab (https://www.glbrc.org/education/classroommaterials/cb2e-converting-cellulosic-biomass-ethanol) to help students explain
the transformations of cellulosic biomass to glucose through the stages of
biomass pretreatment and enzymatic hydrolysis.
LEARNING OBJECTIVES:
Students will be able to understand:
1. Amino acids are the building blocks of proteins and the 3-D shape of
proteins is determined by the amino acid sequence and interactions
between the amino acids
2. The shape of an enzyme determines the function of the enzyme.
Changes in enzyme shape (caused by changes in amino acid sequence,
changes in temperature or pH, etc.) can change the enzyme function.
3. Enzymes fit together with substrates like a “lock and key”
4. In the CB2E lab, enzymes are responsible for hydrolyzing cellulose into
glucose. This is a complex process that we simplify in this activity by
showing an exocellulase enzyme breaking down a cellulose molecule and
later a cellobiase enzyme (B-glucosidase) breaking down cellobiose.
These enyzmes catalyze the breakdown of big carbohydrates into smaller,
simpler, and fermentable sugars.
Necessary background knowledge:
Amino acids are the monomer of proteins just as simple sugars like glucose are
the monomers of carbohydrates. Lego blocks will be representing these
molecules for the enzyme hydrolysis reaction done in the CB2E lab.
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DRAFT, August 2013
Materials List (per group of 4 students):
Each working group should have two plastic bags of assorted Lego pieces.
One bag should have the exocellulase and cellobiase enzymes. It is
recommended to assemble them before class and permanently glue in place with
Duco cement or similar glue.
The Exocellulase enzyme:
Assembly instructions for the exocellulase enzyme:
1. Place a Roof piece on top of a 2X1 piece (both red). Place this on a
4X2 piece (yellow).
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DRAFT, August 2013
The B-glucosidase enzyme:
asfafdasdfasdfafdasdfasdf
Assembly instructions for the B-glucosidase enzyme:
The Cell Wall:





Glucoses are represented by 1X1 Red Legos
Cellulose is represented by a series of connected and attached 1X1 Red
Legos
2X1 and 4X2 red blocks represent many glucoses connected by Hydrogen
bonds
Hemicellulose is represented by black Legos
Lignin is represented by fluorescent green and orange circle Legos
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DRAFT, August 2013
Student Group Activity:
1. Build Cell Wall with help of pictures and assembly instructions
2. Attempt to fit cell wall substrate into cellulase enzymes. Ultimate goal of
this activity will be to liberate glucose molecules to use for fermentation.
At this stage the “key and lock” connection between enzyme and substrate
will be unsuccessful. Describe what cell wall components are getting in
the way.
3. Represent the Pre-treatment phase of CB2E by “heating” up the cell wall
substrate and removing the lignin and hemi-cellulose. Ask students to
draw what the substrate looks like now.
4. Now attempt the “key and lock” connection again between enzymes and
substrate. It should be successful for the exocellulase. This enzyme will
break apart the substrate into two pieces, a small 1X2 piece (actually 2
1X1 pieces stuck together), and a larger 3-piece chunk (a 1X2 on a 2X4
on a 1X2). Have students draw the two products of this reaction (it may
be necessary to tell them that cellobiose will be one of the products.
5. Attempt the “key and lock” connection again between the B-glucosidase
enzyme and the cellobiose. There should be a fit. Students can then
break apart the cellobiose into two glucose molecules.
6. Some hypothetical situations: what if you mutated the exocellulase
enzyme by changing one amino acid
so that this:
became this:
Would this have any impact on the reaction? Explain
7. Some hypothetical situations: what if you mutated the exocellulase
enzyme by changing one amino acid
so that this:
became this:
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DRAFT, August 2013
Would this have any impact on the reaction? Explain
Would altering the structure have an effect on the function of this enzyme?
Explain.
8. What happen if you used the B-glucosidase enzyme with the pretreated
cellulose substrate?
9. What would happen if you raised the temperature of the reaction between
the two enzymes and cellulose from 20C to 40C?
Which of the following would be most likely to occurReaction would slow down
Reaction would speed up
Reaction would stop
Explain why.
10. What would happen if you raised the temperature of the reaction between
the two enzymes and cellulose from 20C to 100C?
Which of the following would be most likely to occurReaction would slow down
Reaction would speed up
Reaction would stop
Explain why.
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