How does gravitational energy change from sea level to an elevated height?

I have no idea why you put this under "Biology" but anyways I will try my best to answer this question.

Gravitational energy or gravitational potential energy is always measured from some reference point, where *gravitational energy is assumed to be zero*
Suppose I place a ball having mass m on the floor. Assuming floor to be the reference level(zero potential level), GE associated with the ball will be zero. But as I lift ball to some height suppose h, GE will be *mgh* were g is acceleration due to gravity.

GE varies linearly with height but only to some extent.

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.