What's the point of ATP synthesis from ADP + P?

[Lo.Lee.Ta.]

Wouldn't you need an ATP to actually add the P to ADP?

...So then nothing would really be accomplished because you'd have to use an ATP to make a different ATP.

Or is there a different type of energy that can add P to ADP?

My book says that the ADP + P reaction uses energy from catabolism (energy-releasing processes)...
So what other type of energy makes ADP join with P?


...And now that I think of it, it doesn't really make sense that an ADP + P reaction could use ATP because then ADP would already be phosphorylated... and wouldn't need that P reactant.

Thanks for the help! :)

 

[ChiralWaltz]

Which part of synthesis are you referring to, glycolysis?

Edit: Simply stated, glycolysis takes 2 ATP's and produces 4 ATP's.

How P gets added to ADP to make ATP:
Glycolysis- Enzymes (hexokinase,phosphofructokinase, ect) also play a role in binding phosphates to ADP.

Citric Acid Cycle- GTP is used to generate ATP in the

Oxidative Phosphorylation- Chemiosmosis step uses the ATP synthase (enzyme site)