These sugar molecules are the basis for more complex molecules made by the photosynthetic cell, such as glucose. Then, via respiration processes, cells use oxygen and glucose to synthesize energy ...

Presence of oxygen Present. Absent or in short supply. Oxidation of glucose Complete Incomplete. The products of respiration still contain energy. Products of respiration Carbon dioxide and water.

Its molecules contain two oxygen atoms. Oxygen is vital for respiration, which is the process that transforms energy from glucose to energy for cells. Oxygen is necessary for burning to occur.