Phospholipid bilayer

[oohpsjin]

Hey guys

I was never able to figure this one out..

 

If the phospholipid bilayer has both a hydrophilic and hydrophobic region, how is it that hydrophobic compounds pass through the plasma membrane so easily (without being stopped by the hydrophilic layer?) whereas hydrophilic compounds need carrier proteins to be transported across the membrane?

 

Any help will be appreciated!

 

Jin

[supafield]

Hey guys

I was never able to figure this one out..

 

If the phospholipid bilayer has both a hydrophilic and hydrophobic region, how is it that hydrophobic compounds pass through the plasma membrane so easily (without being stopped by the hydrophilic layer?) whereas hydrophilic compounds need carrier proteins to be transported across the membrane?

 

Any help will be appreciated!

 

Jin

 

 

Remember, that most hydrophobic substances need a carrier proteins to travel through the blood and in the cytoplasm.... this carrier protein allows the substance to dissolve in hydrophillic conditions...

 

When it gets to the membrane it gets past the hydrophillic part, then passes on it's own through the hydrophobic portion, and meets a second carrier protein inside the cell to pass through the hydrophillic layer inside and in the cytoplasm....

 

I'm sure it's oodles more complicated than this, I'm not a bio major... but for the MCAT.... it explains why protein hormones act from a receptor outside the cell using a second messenger system, why steroid hormones pass right through the cell membrane and why ion pumps and certain channels are required..... So I think understanding it like this will be fine...

[oohpsjin]

makes sense to me. Thanks a lot!