Is glucose a reactant in the aerobic stages of cellular respiration?

No.
Glucose is a reactant in the process of glycolysis. Glycolysis is the breakdown of glucose by enzymes, producing pyruvic acid and releasing energy. Oxygen is not needed in the process of glycolysis, so therefore glycolysis is an anaerobic process. Oxygen is not required in cellular respiration until electron transport.
Therefore:
Glucose is not a reactant in the aerobic stages of cellular respiration, but it is a reactant in the initial anaerobic stages of cellular respiration.

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