The dialysis bag will remain the same size in a isotonic solution.
*The key function of each of the two photosystems is to absorb light and convert the energy of the absorbed light into redox energy, which drives electron transport.
In PS II (the first photosystem in the sequence), P680 is oxidized (which in turn oxidizes water), and the PS II primary electron acceptor is reduced (which in turn reduces the electron transport chain between the photosystems).
In PS I, the PS I primary electron acceptor is reduced (which in turn reduces other compounds that ultimately reduce NADP+ to NADPH), and P700 is oxidized (which in turn oxidizes the electron transport chain between the photosystems).
