ATP and Coupled Reactions
Many reactions in cells are endothermic (require energy), such as protein
synthesis.
The energy comes from the breakdown of ATP (adenosine triphosphate);
this process provides energy and so is exothermic.
When the energy released by an exothermic reaction drives an endothermic
reaction these two reactions are said to be a coupled reaction.
What is ATP (Adenosine triphosphate)?
The ATP Cycle
How do we get energy from ATP?
How much energy do we get from one ATP molecule?
Every time ATP is broken down into ADP, 31 kJ/mol of energy is released.
What is ATP used for?
There are three distinct uses for ATP:
1. Chemical Work
- ATP supplies the energy needed to synthesize
macromolecules
2. Mechanical Work
- ATP supplies the energy needed to permit
muscles to contract, cilia and flagella to beat,
chromosomes to move and other functions
3. Transport Work
- ATP supplies the energy cells need to pump
substances across the cell membrane
An Example of ATP at Work - The Sodium/Potassium Pump
Some substances can move across the cell membrane very easily, such as
water. (Usually with the concentration gradient.)
Other substances require energy to move substances against the
concentration gradient. This is also accomplished with the help of special
proteins.
A common example is the sodium/potassium pump. This pump maintains
an imbalance of sodium and potassium in cells. Especially in nerve and
muscle cells.