"Glycolysis" strikes fear into many undergrad biology
students because it presents them with an abstract series of reactions
and molecules which are difficult to visualize and therefore incorporate
into a coherant biochemical framework. This exercise has each student
taking responsibility for a single molecule in the series, requires
them to know its precursor, the enzyme which created it, the enzyme which
will act on it, the product of that action, and the significance of the
bond structure, particularly those involving phosphate. They are
then to describe these features to their fellow students in sequence.
This strategy for teaching glycolysis has received many positive reviews
from students who have used it.
Here is the key for the identities of the elements in the models:
| color of ball | element | number of bonds required |
| black | carbon | 4 |
| red | oxygen | 2 |
| yellow | hydrogen | 1 |
| purple | phosphate (PO4) | it has 5 bonds... |
For the construction, remember that in straight chain illustrations of the chemical structures, the carbon back bone is vertical with vertical bonds from each carbon projecting away from the observer and horizontal bonds projecting towards the observer.
Here is the sequential listing of the molecules of glycolysis:
1) Glucose
2) Glucose-6-phosphate
(G-6-P)
3) Fructose-6-phosphate
(F-6-P)
4) Fructose-1,6-bisphosphate
(F1,6bP)
5) Dihydroxyacetone
phosphate (DHAP)
6) Glyceraldehyde-3-phosphate
(33GAP)
7) 1,3-bisphosphoglycerate
(1,3bPGA)
8) 3-phosphoglycerate
(3-PGA)
9) 2-phosphoglycerate
(2-PGA)
10) Phosphoenolpyruvate
(PEP)
11) Pyruvate
12) Lactic acid
13) Acetaldehyde,
Carbon
dioxide & Ethanol
Once
students have constructed the assigned molecule, and learned the enzymes
and related molecules, the models are laid out in sequence on a big table,
and students in succession gave the following information:
1) The name of the molecule they had constructed
2) Its characteristic features
3) How it differs from the previous molecule
5) The enzyme which produced it
6) How it will be changed into the next molecule
and why
7) The name of the enzyme which performs this
change and the meaning of the name of the enzyme.
Students were to discuss selected phosphorylated molecules (i.e. glucose 6 phosphate, 1,3 bisphosphoglycerate, and phosphoenolpyruvate), naming and discussing the bonds by which phosphate is attached, and the relative energy content in each type (phosphoester, phosphoanhydride, resons for PEP's unusual energy). The products of hydrolysis of these bonds was demonstrated and discussed.
We have taken pictures of this exercise since 1997. Here they
are, the students holds his/her molecule constructed in November of 2002,
2001, 2000
and 1997 (the latter taken
with a less adequate digital camera...).
Videos on glycolysis from Films for the Humanities and Sciences series which review the process are:
VIDT QH 633 .C45 1992 pt.1 Cell and Energy (Series Title-Cellular Respiration)
VIDT QH 633 .C45 1992 pt.2 Glycolosis 1 (Series Title-Cellular Respiration)
VIDT QH 633 .C45 1992 pt.3 Glycolosis 2 (Series Title-Cellular Respiration