Photosynthesis occurs in plant cells inside the organelles called chloroplasts. These chloroplasts contain a green substance named chlorophyll. This substance absorbs light energy and converts it into chemical energy that is used in order for the cell to function. Chlorophyll mostly absorbs red and blue wavelengths and cannot absorb green wavelengths, which gives it the green color. Adenosine triphosphate, ATP, is what transfers the chemical energy within cells.
Cellular respiration, however, takes place in the organelles called mitochondria of animal cells. Cellular respiration is the process of oxidizing food molecules to water and carbon dioxide. Inside mitochondria, the energy of food molecules is converted into ATP. Just like plant cells, ATP is transferred throughout the cell in order for the cell to perform its activities. Overall, without ATP both plant and animal cells wouldn't be able to function properly.