Photosynthesis is the process where a plant consumes water, carbon dioxide and light energy to produce glucose and oxygen. During cellular respiration, the chemical energy in the glucose molecule converts into a form the plant can use for growth and reproduction.
According to the University of Michigan, the process of photosynthesis consists of two main groups of reactions: the "light reactions," that require light energy to operate, and the "Calvin cycle," that takes carbon dioxide and converts it into organic molecules. During cellular respiration, oxygen combines with sugars to break molecular bonds, releasing the energy (in the form of adenosine triphosphate, or ATP) contained in those bonds.
In the first step of respiration, called glycolysis, the glucose molecule breaks down into two smaller molecules, called pyruvate, and releases energy in the form of ATP. In the second step of respiration, the pyruvate molecules are rearranged and combined and rearranged again in a cycle. In the last step, the molecules produce carbon dioxide, and electrons are pulled off and passed into an electron transport system that generates a lot of ATP for the plant to use for growth and reproduction. A series of metabolic pathways in the cell's mitochondria result in the further breaking of chemical bonds and the liberation of ATP.