1. Chapter 9 Energy in a Cell
Section 1
The Need For Energy

2. Cells need energy to perform a variety of functions such as active transport, movement and division.

3. ATP
The cell gets the energy that it needs from a molecule called adenosine triphosphate, or ATP.

4. ATP Structure
ATP is made up of an adenosine group bonded to three phosphate groups. There is a lot of energy stored in the bond between the last 2 phosphate groups.

5. ATP-ADP Cycle
When the bond between the last 2 phosphate groups in ATP is broken, energy is released to the cell. A new molecule, ADP is formed. ADP can bond a phosphate group to store energy for the cell.

6. ATP-ADP Cycle When the cell needs to store energy:
ADP + P + Energy  ATP
When the cell needs to release energy:
ATP ADP + P + Energy

8. How Do Cells Tap Into Energy Stored In ATP?
Cells use proteins to capture the energy of ATP. Once energy is released, the protein releases ADP back into the cell.
With out the protein, the cell would not be able to use ATP.