As the electrons pass through the electron transport chain between Photosystem I and II, they use their energy to pump into the creating an electrochemical gradient, and making that space very (acidic/basic).

protons /H+

thylakoid membrane of the chloroplast

acid.

Explanation:

This is chemiosmosis. And the ultimate aim is to synthesis ATPs. Proton Motive Force generated from the electron transport chain continuously pump protons(H+) from the stroma into the thylakoid membrane of the chloroplast,

The build up of  protons/H+ generated electrochemical gradients between this  space and the stroma.

Therefore proton/H+ diffused down the gradient into the stroma. The energy generated from the downwards diffusion is used by the ATPase synthase to synthesize ATPs from ADP and inorganic phosphate (Pi), to be used in Calvin Cycle for CHO, productions.

The protons/H+ pumped by PMF and  concentrated in the thylakoid memebrane is obtained from the  split of Hydrogen atoms  to electrons(e-) and H+. since pH is negative Log of [H+], therefore the space will be acidic from large concentration of H+/protons.

the generally accepted parts of modern cell theory include: all known living things are made up of one or more cells. all living cells arise from pre-existing cells by division. the cell is the fundamental unit of structure and function in all living organisms.