Cellular respiration and photosynthesis are two processes that are utilized widely by most living cells, both animal and plant. Animal cells use cellular respiration, where a glucose molecule is oxidized by an oxygen molecule. The resulting products are energy in the form of ATP (adenosine triphosphate) and carbon dioxide and water, which are waste products. Photosynthesis is the process utilized in the chloroplasts of plant cells, where carbon dioxide and water undergo a chemical process with radiant energy, usually from the sun. The resulting products are energy stored in the form of a glucose molecule, and oxygen, which is given off as a waste product. It is interesting to observe the waste products given off by each process are the essential requirements each process require to begin. Together, cellular respiration and photosynthesis represent a cyclical processing of oxygen. This is why we should be concerned about deforestation and eradication of rain forests, because they are a major supplier of the oxygen in the Earths atmosphere.
6CO2 + 6H2O -------> C6H12O6 + 6O2
In photosynthesis in presence of sunlight plant utilizes carbondioxide and water to produce carbohydrates and oxygen.
Some carbohydrates is utilized by the plant and remaining form food which is utilised the living organism...
And the Oxygen is released out by the plant during day time.
The released Oxygen is utilised by the living organism and undergo the process of respiration.
In respiration the Oxygen from the environment if inhaled by the living organism and which is carried to the cell and perform cellular respiration.
In living organism the Oxygen is used for breaking down the biochemical energy and convert them into ATP which is utilised by the body to perform work.
For example in living organism the oxygen is utilized in the first step of cellular respiration that is Glycolysis...
C6H12O6 + 6O2 -------> 6CO2 + 6H2O.
C6H12O6 + 2NAD+ + 2ADP 2Pi --------> 2 Pyruvate + 2ATP + 2NADH + 2H+
NOTE:- In plants Oxygen is released via Photosynthesis and that oxygen is inhaled and utilized by the living organism via respiration.
(Both are complex process)