The electron transport chain between photosystem II and photosystem I generate a proton gradient which drives ATP synthase known as

Complex V

Explanation:

In the mitochondria of normal cells, the ATP synthase, also referred to as Complex V of the electron transport chain, synthesizes ATP from ADP and phosphate by using a proton gradient. The electrons transferred by the complexes I, III, and IV extrude protons to the intermembrane region, thereby generating a proton electrochemical gradient that is used by this Complex (V) when protons pass back across the inner membrane to the matrix space. The complex V is composed of two major functional domains named F0 and F1.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!

i think this picture will you.