Start with the big picture. Don't immediately inundate the students with all the specific details of glycolysis. Give them an overview of how glycolysis fits into the big picture of life sustenance, why it's important and why they should care. Some areas you should touch on at this point include: the definition of cellular respiration; how glycolysis fits into the respiratory process (what comes before and after); and the initial reactants and final products in glycolysis. You should also introduce the overall chemical equation for glycolysis, which is:
Glucose + 2 [NAD+] + 2 ATP + 4 ADP + 2 Phosphate ' 2 Pyruvate + 2 NADH + 2 [H+] + 2 ADP + 4 ATP + 2 H2O.
You could also cancel out the ATP/ADP to make this equation:
Glucose + 2 [NAD+] + 2 ADP + 2 Phosphate ' 2 Pyruvate + 2 NADH + 2 [H+] + 2 ATP + 2 H2O.
Look at the chemical steps within glycolysis specifically. Again, don't immediately go through every chemical intermediate in the cascade. It will be meaningless to the students without context. Focus on the big events first. For example, you could simplify the glycolysis pathway as: Glucose ' Fructoses ' Phosphoglycerates ' Pyruvates. Alternatively, you could initially present the pathway even more simply as: Glucose ' Phosphates ' Pyruvates. Point out where ATP is used or created in the pathway (it is used at the Glucose and Fructose stages, and created at the Phosphoglycerate and Pyruvate stages). Also point out where NAD+ is reduced to NADH (in the Phosphoglycerate stage) and where water is produced (between the Phosphoglycerate and Pyruvate stages).
Add details as appropriate. At this point, the students should have a good idea of the context of glycolysis and a good framework on which to hang more details. The level of detail you include depends on the level of your students. You can get as specific as you would like in terms of chemical intermediates and important enzymes within the glycolytic cascade.