2026-08-17 12:14:19: Membrane Permeability

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biology/Cell Structure and Function/Membrane Permeability.md

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+[[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).