Apiece of bread held in the mouth begins to taste sweet as large carbohydrate molecules are broken down into smaller sugars. these reactions are examples of

The answer to this question would be hydrolysis

There is amylase enzyme inside saliva that will break down starch into maltose sugar. Maltose is the sugar that causing the sweet sensation in the tongue. Since it will take for the reaction to happen, the sweet taste only appears after a few moments after you chewing the bread.
The reaction that was catalyzed by amylase is hydrolysis.

Mg is used to measure mass

Atp is is our little "pocket" of energy. of course, if you have too little, then it means you have too little energy, and you'll pass out. the way to not have enough, is to have no energy sources (glucose, fats, proteins). you can't have too many atp molecules. cycles like the krebs cycle produce it, but if you have too much of any substrate (or too little for that matter), the cycle stops and atp is no longer made (it stops until substrate levels are such that the process can go on). in any case, this is unlikely since atp is constantly hydrolyzed and remade, even while you're asleep. you won't have too much. if you have zero, you are dead or dying.