The fuel source that gives energy to all the activities of cells in organisms on Earth is ATP (Adenosine Triphosphate).

While other fuels like glucose and fatty acids are used to create ATP, ATP itself is the direct energy currency of cells. It's like the "money" cells use to pay for all their activities, such as:

* Muscle contraction

* Protein synthesis

* Active transport

* Cell signaling

* Nerve impulses

So, while glucose and other fuels provide the raw materials for ATP production, it's ATP that directly powers the cell's functions.