2. Maintain (repair) themselves
4. Move (or move things in and out of the cell) & change shape
5. Metabolism (Breaking down bigger molecules into smaller molecules, and getting energy from these molecules)
Cells chemically " burn" food molecules (glucose) to extract energy to do #1-5 above.
This "burning" takes place slowly, in hundreds of steps to keep cells from dieing of too much heat. The energy is released from the C-H bonds of glucose (simple sugar). Some of the energy that is released is used to make ATP. Energy not used to make ATP is released as heat.
ATP--------Short term energy storage molecule. All cell processes are powered by ATP. Our food energy must always be converted to ATP energy for use by the cell!