[[Cell Structure and Function]]
# Summary
* Selective permeability comes from hydrophobic interior of nuclear membrane since phospholipids have fatty acid tails which are non polar
* Small non polar molecules ($N_2,O_2,CO_2$) pass through freely
* Small non charged polar molecules ($H_2O,NH_3$) can slip through in small amounts
* Ions and and large polar molecules can't cross  and require channels or transport proteins.
* Cell walls in bacteria, archaea, fungi and plants provides structure, protects against osmotic lysis and acts as a permeability layer for some substances.

![[Pasted image 20260817121113.png]]![[Pasted image 20260817121129.png|526]]

Cell wall material:
* Bacteria - peptidoglycan
* Archaea - various polymers (not peptidoglycan)
* Fungi - chitin
* Plants - cellulose
Cell walls maintain shape and mechanical strength, permeability layer, protection from osmotic lysis (rupture via influx of water).