She would find oxygen (O2) in the test tube because plants give off oxygen
I think it is because it's easier to "control". Like the books usually said that the nucleus is the control center of the nucleus, so if the nucleus located at the center or near center of the cell. So like easy contact, easy control, easy communication etc.
Answer:
Dropping in energy levels
Against their concentration gradient
Explanation:
The pair of electrons are passed down a series of electron carriers of progressively lower energy levels through a series of redox reactions in the electron transport chain, releasing energy (electrical potential energy) to be used by H+ pump for the active transport of H+ ions (aka protons) from a region of higher concentration to a region of lower energy level against its concentration gradient.