Which of the following is part of the urinary system?
a. liver
b. kidneys
c. stomach
d. gallbladder?

The liver doesn't really help out with the urinary system. The stomach, as you already know, is a part of the digestive system, where a lot of proteins are digested. The gallbladder is where your bile (a digestive "juice") is stored, so that has nothing to do with the urinary system as well.

Your kidneys, though, are a part of the urinary system, and that is where all the unwanted stuff in your blood is transferred to the urine.

Hope I helped!! xx

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.