Hallo :3
Your question is related to cellular respiration/photosynthesis.
The conversion of ADP to ATP is scientifically known as chemiosmotic phosphorylation. This reaction, which takes place in the cytoplasm, ensures that ADP (low energy) is converted to ATP(higher energy). ATP, the currency of life, is higher at storing energy. This reaction serves as an energy recycling process to build a better molecule.
