ATP will release or give off energy when it releases a phosphate molecule. Since a cell can add or subtract a phosphate group, it has a way of storing and releasing energy. Most cells have only a small amount of ATP. It can't be used to store energy for long periods of time. These ATP stores last only a few seconds after which the breakdown of PC provides energy for another 5-8 seconds of activity. Combined, the ATP-PC system can sustain all-out exercise for up to 10-15 seconds and it is during this time that the potential rate for power output is at its greatest. These ATP stores last only a few seconds after which the breakdown of PC provides energy for another 5-8 seconds of activity. Combined, the ATP-PC system can sustain all-out exercise for up to 10-15 seconds and it is during this time that the potential rate for power output is at its greatest. Hence, ATP cannot be stored easily within cells, and the storage of carbon sources for ATP production (such as triglycerides or glycogen) is the best choice for energy maintenance. Lipids are molecules that can be used for long-term energy storage. Most cells have only a small amount of ATP. It can't be used to store energy for long periods of time. It is more efficient for a cell to keep a small supply of ATP. Cells can regenerate ATP from ADP as needed by using the energy in carbohydrates like glucose. The ATP molecule is just like a rechargeable battery. When it's fully charged, it's ATP. When it's run down, it's ADP. However, the battery doesn't get thrown away when it's run down–it just gets charged up again. Living organisms use two major types of energy storage. Energy-rich molecules such as glycogen and triglycerides store energy in the form of covalent chemical bonds. Cells synthesize such molecules and store them for later release of the energy. Monosaccharides
Monosaccharides contain just one sugar unit, so they're the smallest of the carbohydrates. (The prefix "mono-" means "one.") The small size of monosaccharides gives them a special role in digestion and metabolism. In a process called cellular respiration, chemical energy in food is converted into chemical energy that the cell can use, and stores it in molecules of ATP. ... When the cell needs energy to do work, ATP loses its 3rd phosphate group, releasing energy stored in the bond that the cell can use to do work.