Originally posted by mlprior
...anything about passive transport via protein pathway through phospholipid layers in eukaryotic cells?
Google Scholar is failing me tonight!
Eukaryotic cells are the more "advanced" type of cell which has various specialty compartments called organelles. These is what animals and plants are made of. Bacteria, on the other hand, are prokaryotes. They have no nucleus and their DNA just kinda floats semi freely. Eukaryotes have the DNA packaged up in a nucleus.
The "skin" of a cell is made of phospholipid molecules arranged in a bilayer formation, with the polar "heads" facing inside and outside the cel, and the nonpolar "tails" are inside the "skin" itself. Try searching for "micelle".
Now, humans have holes in our bodies which are intended to allow substances in and out of our bodies. The mouth takes in food, the nostrils take in and exhale air and CO2, etc. If you want to put something inside a person without using these holes you need to punch a hole in the skin with a needle or something. However you can put things "inside" the person by having them swallow it, or breathe it, or stick it up their butt, or whatever.
Cells have similar holes in their membranes, and those holes are held open by proteins. Those proteins can function in active or passive ways. Active proteins are like your mouth and throat; they actively move substances from one side to the other. Passive proteins are more like your ears; things can go inside, but there is no mechanism in the ear pushing things out or pulling them in.
So, in short, you are asking about holes in plant/animal type cells' skins made of proteins but which are unpowered portals for whatever to pass in or out of the cell via diffusion.