Oxygen is so electronegative when water is made that a HUGE amount of heat would be released if there were no intermediate steps and the reaction was a one-step, straightforward process.
Since the electrons come from a molecule (glucose), where the electrons are "pulled" more weakly by each atom in glucose, the electrons release energy when they change from a weaker-pulling molecule (glucose) to a molecule where the electrons will be pulled much closer and much more strongly (water) because the hydrogen molecules don't pull the electrons as nearly as hard as oxygen. In the case of water, that energy released is so big it's almost like an explosion.
To put it in an analogy, oxygen is like gravity and we are the electrons on top of a building. Without the intermediate steps in electron transfer, it would be like jumping right off the building and falling flat on the ground. The intermediate steps in the electron transfer are like stairs to break our fall. Instead of falling straight down, we fall down with stairs so we only get hurt little by little.
Likewise for the electron transfer process. We wouldn't want electrons going straight down to oxygen because then we would EXPLODE. And that's not good.
Since the electrons come from a molecule (glucose), where the electrons are "pulled" more weakly by each atom in glucose, the electrons release energy when they change from a weaker-pulling molecule (glucose) to a molecule where the electrons will be pulled much closer and much more strongly (water) because the hydrogen molecules don't pull the electrons as nearly as hard as oxygen. In the case of water, that energy released is so big it's almost like an explosion.
To put it in an analogy, oxygen is like gravity and we are the electrons on top of a building. Without the intermediate steps in electron transfer, it would be like jumping right off the building and falling flat on the ground. The intermediate steps in the electron transfer are like stairs to break our fall. Instead of falling straight down, we fall down with stairs so we only get hurt little by little.
Likewise for the electron transfer process. We wouldn't want electrons going straight down to oxygen because then we would EXPLODE. And that's not good.