If the hydrophobic hydrocarbon chain of the phospholipid prevents the movement of polar molecules through the membrane. Why does the hydrophilic phosphate head of the phospholipid not prevent the movement of non-polar molecules?
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$\begingroup$ You might be interested in this. $\endgroup$– another 'Homo sapien'Nov 29, 2016 at 15:33
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1$\begingroup$ See if this helps: biology.stackexchange.com/questions/52371/… $\endgroup$– bpeditNov 29, 2016 at 17:59
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5$\begingroup$ Possible duplicate of Why lipophilic molecules can pass phospholipid bilayer, in spite of 2 hydrophilic layers? $\endgroup$– user24284Apr 30, 2017 at 8:43
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$\begingroup$ Polar molecules needs electrochemical gradient and protein carrier. ...whereas non polar molecules needs kinetic energy and these molecule continuously bouncing to come out from the cell membrane through the channel provide by lipoprotein structure of cell membrane and concentration gradient also effective for movement of molecules all types of molecules. $\endgroup$– lovishaJan 22, 2018 at 9:03
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1 Answer
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The plasma membrane consists of hydrophobic and hydrophillic characteristics. Towards the outsides, they are hydrophillic, so they can create bonds with water. The insides are hydrophobic, allowing no water inside and keeping them tight together due to the polar forces.
An non-polar particle (if small), can pass through this because it does not interfere with the hydrophobic/hydrophillic (polar) nature of the plasma membrane. However, polar particles would not have the opportunity to move in, because the insides (hydrophobic) are literally afraid of water, or charges, don't allow polar substances to pass through.
So only hydrophobic (nonpolar), gases, and small particles (nonpolar) can pass through. There are exceptions of $H_2O$ passing through the membrane in small amounts because their electric charge is very minor.
