If several types of pea plants with the genotype TTYy are crossed with pea plants with the genotype Ttyy, what percentage of The Offspring will be expected to have the TTYy allele combination?

They must use the scientific method

Aneutral atom must have the same number of neutrons and protons? no, they must have the same number of protons and electrons

Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.