Answer:
I can’t answer all of them, but I’ll answer the oxygen ones.
The mitochondria uses oxygen. In mitochondria, this process uses oxygen as a waste product. They are organelles that act like a digestive system which takes in nutrients, breaks them down, and creates energy rich molecules for the cell.
I hope this helps, even though I only answered 3 of your questions!!
I think it's the nucleus. Isn't the nucleus the brain of the cell?
