It makes sense that cell membranes are made of phospholipids because water cant mix in with lipids, so the phospholipids will be able to effectively block out any unwanted water or chemicals suspended in water outside of the cell.
ATP has more energy potential. It is like a very strong, charged battery. The most energy is stored in the 2nd and 3rd phosphates. If one is released, it becomes ADP. That is like a weak battery.
carbon, the fundamental component for all the macromolecules.