Glycolysis, or the Embden-Meyerhof Pathway is the process by which most living things obtain
energy from the ubiquitous sugar Glucose.
Embden-Meyerhof-Parnas Pathway
Glycolysis
Glucose
1 ATP
|(
| >ADP + Pi
V
Glucose-6-Phosphate
2
|
|
V
Fructose-6-Phosphate
3 ATP
|(
| >ADP + Pi
V
Fructose-1,6-Bisphosphate
4
_________
/ \
/ \
V V
Dihydroxy Acetone 5-----> Glyceraldehyde-3-Phosphate
Phosphate Pi_ 6 NAD
\|(
| >NADH
V
1,3-Bisphosphoglycerate
7 ADP + Pi
|(
| >ATP
V
3-Phosphoglcerate
8
V
2-Phosphoglcerate
9
|\_>H2O
V
Phosphoenolpyruvate
10 ADP + Pi
|(
| >ATP
V
Pyruvate
Enzymes
1. Hexokinase or Glucokinase
2. Phosphoglucose Isomerase
3. Phosphofructokinase
4. Aldolase
5. Triose Phosphate Isomerase
6. Glyceraldehyde-3-Phosphate Dehydrogenase
7. Phosphoglycerate Kinase
8. Phosphoglycerate Mutase
9. Enolase
10. Pyruvate Kinase
Products per molecule of Glucose:
2 ATP molecules
2 NADH molecules from reduction of two molecules of NAD
2 Pyruvate molecules
The ATP yielded by the reactions of glycolysis is produced by a mechanism called substrate level
phosphorylation. The NADH molecules must be oxidized regenerating NAD so that more glucose can be broken
down. There are two possible mechanisms for this regeneration:
Krebs Cycle
In the Krebs Cycle pyruvate is converted to Aceytyl-CoA which undergoes a series of reactions
producing more NADH, as well as another electron carrier known as FADH, and a molecule of GTP. The electrons
on NADH are then used to produce more ATP during chemiosmosis phosphorylation (also known as Oxidative
phosphorylation).
Fermentation
In fermentation pyruvate, or a pyruvate derivative, acts as the terminal electron acceptor. It accepts
the high energy electrons on NADH, regenerating NAD. Fermentation can produce a variety
of compounds, those prodced depends on the type of organisms. Human fermentation produces lactic acid,
yeast can produce ethanol. Some bacterial species produce butane-diol. These types of fermentation are by no
means limited to the organisms mentioned, and they are not the only possible fermentation pathways.