To add to Kong's explanation
In organisms energy production - that is not biochemical but chemiosmotic - requires a double membrane to produce a conc gradient with H+ or protons. We see these double membranes in Mitochondria (eukaryotes use this organelle for oxidative respiration), Chloroplasts (the organelle this forum has been talking about) and even in some prokaryotes (bacteria)
in just scratching the surface- In green plants
photons hit the pigment - chlorophyll is one example (different types depending on species) - the pigment becomes "excited" of course this requires the light to be a specific wavelength - chlorophyll absorbs in the extremes of the visible light spectrum of the EMS & reflects in the middle - hence green plants
The pigment when excited "transfers" electrons to a series of proteins in one of membranes of the chloroplast - these series are called Photosystems (I & II) & there are several results of this process: one you've mentioned in the photosynthesis equation - water will breakdown into Oxygen gas and Hydrogens
the other is the part that "powers"
H+ are pumped against the gradient into the interior of the thylakoid - there is a high conc of them there and they want to get out - so they passively go through an ATPase to produce ATP
anyway - long story short - products of these photosystems (ATP & electron carriers like NADPH) are used in either a C3 or C4 cycle (Calvin) to produce glucose
I really shorten this - a good resource for cellular biology is Molecular Biology of the Cell by Alberts et al
As far as isolating chloroplasts - not to hard - usually done in an undergraduate cell biology course. Any cell biology lab manual will probably have students blending some spinach to isolate chloroplasts. An old manual would be Gasque (~1989). There's a lab in there for isolating chloroplasts. He's an old prof of mine. Went to his website and he had a link to an online cell biology lab manual from Gustavus Adolphus College http://homepages.gac.edu/~cellab/chpts/chpt8/ex8-1.html
I gave it a glance, looks similiar to what I did a long time ago. Also explains how to remove outer membrane of the chloroplast.
The concept of active transport (proton pump) to produce a conc gradient which then can use passive transport (facilitated diffusion through an ATPase or other proteins) is a commonly used process to convert energy in the biotic world.