. With the emergence of photosynthesis on earth, molecular oxygen began to accumulate slowly in the atmosphere.

. The presence of free oxygen made possible the evolution of respiration.

. Respiration releases great deal of energy and some of this energy is used in the formation of adenosine triphosphate (ATP) molecules.



. ATP is a kind of chemical link between catabolism and anabolism.

. The process of photosynthesis helps understand some of the principles of energy transformation (Bioenergetics) in living system.

. Photosynthetic organisms use solar energy to synthesize organic compound (such as carbohydrates) that can not be formed with out the input of the energy.

. Energy stored in these molecules can be used later for cellular processes and can serve as the energy source for all forms of life.

. Glycolysis and respiration are the processes where by the energy stored in carbohydrates is released in a controlled manner.

. So the photosynthesis act as an energy capturing while respiration as an energy relating process