Subject: In cellular respiration, what atoms lose the electrons that are carried ?

In the chemical reaction for cellular respiration, glucose is broken down and 
electrons are picked up and carried about until they  are finally accepted by 
oxygen. Whose electrons were they  to begin with? Did they come from the  carbon 
in glucose or were they part of the hydrogen atoms that are in the glucose 
molecule? or both? I am asking because I am a biologist trying to teach this 
reaction to tenth graders and I can't answer this question!

Re: In cellular respiration, what atoms lose the electrons that are carried ?