Example dimensions: leaf 60 mm long, drop 3 mm wide and 2 mm high, Paramecium 200 μm long. A shared metre-based coordinate system keeps the leaf 20 times the drop’s width and the cell 1/15 of that width. These are explicit reference sizes, not universal leaf or drop dimensions.
The horizontal slipper-shaped cell follows the supplied reference. It scales continuously at its physical size, without a stage-based opacity fade, and is hidden only below a projected length of 2 CSS pixels. Colors, transparency and organelle shapes support learning, rather than reconstructing a measured cell.
The membrane uses an example thickness of about 7 nm; underlying pellicle structures are omitted. Oxygen and carbon dioxide diffuse through the lipid layer; switch between voltage gating, ligand gating and alternating-access carriers. Ion passage obeys gate states; a carrier never opens both sides simultaneously. This slowed general membrane teaching view is not a measured protein inventory or atomic structure of this Paramecium. Protein dimensions, counts, rates and trajectories are illustrative.