Final answer:
ATP is the primary energy source for cells, acting as the direct energy currency, whereas glucose is metabolized to recharge ATP with energy.
Step-by-step explanation:
The primary energy source for cells is ATP, or adenosine triphosphate. While glucose serves as a key energy source that cells break down to release energy, it is ATP that acts as the direct energy currency within the cell. When cellular respiration occurs, glucose is metabolized, and energy is stored in ATP molecules. This ATP then provides the necessary energy for various cellular processes. In photosynthesis, the energy of a photon is absorbed by chlorophyll, initiating the process of converting sunlight into chemical energy that is eventually stored in glucose, which can also be later converted into ATP.