You can see the structures within the organelles of the cells (e.g the structure within a mitochondria) with an electron microscope as it has a much higher resolution than light microscopes.
I'm pretty sure the bottom one is faciliated diffusion. Try searching up your answer so sorry I couldn't help more, but I hope that does help you out a bit:)
Flatworms absorb oxygen by diffusion mechanism through their
skin to the cells in their bodies. Since flatworms do not have a circulatory system,
their bodies' cells are positioned close to the skin to ease the uptake of
oxygen from surrounding fluids or water.
There are so many examples for that in different areas, like TPBi experiment carried out in our lab recently.Here's one link: http://www.alfa-chemistry.com/tpbi-cas-192198-85-9-item-282866.htm
