What is the primary energy source for cells?

[wheel]

I think ATP is just an instant source of energy. We can't say that it's the primary source of energy for cells. Without ATP, cells still can harvest energy from glucose. So, I suppose the real primary source of energy for cells is glucose. Perhaps, we can say ATP is the primary supply of energy for cells, but certainly not primary source. In fact, it's just a matter of choice of words.

[Borisfen]

"ATP" is definitely a strange answer.
Human body uses >50kg ATP daily (by hydrolysing and re-synthesizing). ATP is not energy source, it is an energy transmitter.

The primary energy source for life on Earth is clearly sunlight (with exception of some peculiar life forms on the sea bottom near hot springs)

The primary energy source for some specific cells cannot be defined unless the type of cells is defined.

Bad question, bad answer.

[mcar]

From Borisfen: The primary energy source for life on Earth is clearly sunlight (with exception of some peculiar life forms on the sea bottom near hot springs)

The primary energy source for some specific cells cannot be defined unless the type of cells is defined.

I agree. Recall our energy and food relationships and the fact that plants being the major producers and their ability to absorb the radiant energy from the sun. As plants are eaten by the consumers (primary consumers or herbivores definitely), this energy undergo transformation becoming a form chemical energy and thus be subjected again to series of metabolic reactions (i.e. glycolysis, TCA cycle: processes that can provide us the ATP) that take place inside are very own cells. Therefore, our cells and its organelles are all involved in doing all the metabolic processes required to maintain life and the energy they are using went on series of transformation first before we can successfully benefit from it.