ATP
Adenosine triphosphate, the cell's short-term energy carrier. Removing its end phosphate releases usable energy and leaves ADP.
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Analogy
A rechargeable battery that is charged in one place and used in another.
Example
A resting adult recycles roughly their own body weight in ATP each day.Each ATP molecule is reused many times.
In practice
Muscle contraction, active transport and making DNA all run on ATP.
Practice
Flashcards
- What happens when ATP is hydrolysed?The end phosphate is removed, forming ADP and a free phosphate, and energy is released.
- How do cells make an energy-needing reaction go ahead?By coupling it to ATP breakdown so the overall delta G is negative.
Interview questions
- Describe how ATP lets a cell carry out reactions that would not happen by themselves.
- Hydrolysis has large negative delta G
- Coupling makes overall delta G negative
- ATP is regenerated from ADP
Questions people ask
Why is ATP called the energy currency of the cell?
Because nearly every energy-needing job in a cell is paid for with ATP, whatever the source of the energy was. Food, light and chemicals all end up being used to make ATP. Like money, it is a common unit that can be spent on many different tasks.
Why does breaking ATP release energy?
The three phosphate groups are all negatively charged and crowd close together, so the molecule is under strain. Removing the last one relieves that repulsion, and the products are more stable. The energy comes from this stability change, not from the bond itself being special.