Final answer:
Cellular respiration breaks down glucose to produce ATP, the main energy source for cells, and is more efficient with oxygen.
Step-by-step explanation:
Cellular respiration is the metabolic process that provides cell energy by breaking down glucose to produce ATP (adenosine triphosphate). In the presence of oxygen, this process is much more efficient, yielding a large amount of ATP, which is essentially the energy currency for the cell. Glucose is especially important as fuel for nerve cells and red blood cells, which primarily use glucose. The catabolic pathways involved in this process release energy stored in the chemical bonds of glucose, allowing for the production of ATP.