Carotenoids are red, orange, or yellow pigments found in many plants. we know that plants contain chlorophyll a and b. what is the benefit of having multiple pigments within the leaves of plants?

Multi color plants and flowers have a benefit since some predators did not like certain colors, also, when they are trying to reproduce the colors attract pollinators.  

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.