How long does it take for the cell convert glucose into energy once the glucose has entered into the cell?

 

Ie, how much time passes between the glucose molecule's endocytosis and the end of the molecule's electron transport chain?

depends. the molecules could effectively immediately be converted to energy or it couldd hang around in there for decades(although that is unlikely).

 

you can't really approach the problem by following an individual molecule, you need to take a statistical average of many individual molecules to get the residence time. just take the number of glucose molecules present within the cell and divide this by the rate at which they are consumed. this should give you an average residence time.