(A) Electron micrograph of a human cell section showing three mitochondria. (B) Scheme of the protein complexes that form the ETS, showing the mitochondrial membranes in blue and red; NADH ...

Molecules and ions pass in and out of the cell through tiny openings in the cell wall. Although the holes are too small to be seen with an electron microscope, their size has been measured ...

Moreover, nearly all eukaryotic organelles are separated from the rest of the cellular space by a membrane ... electron microscopy to take a snapshot through a thin cross-section or slice of a cell.