Phosopholipids in Salty solutions

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AI Thread Summary
The discussion revolves around calculating the areal charge density and surface potential of a phospholipid bilayer membrane composed of 90% uncharged lipids and 10% charged lipids in a 100mM NaCl solution at 25 degrees Celsius. The user expresses confusion about how to model the membrane and apply the percentage of charged versus uncharged lipid head groups in their calculations. They consider using concentric spheres to find the potential but are uncertain about how to approach the charge density calculation. The conversation highlights the need for clarity on the application of relevant equations and modeling techniques for this type of membrane system. Understanding these concepts is crucial for accurately determining the membrane's electrochemical properties.
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Homework Statement


Consider a phospholipid bilayer membrane consisting of a mixture of 90% uncharged lipid and 10% singly charged acid lipid. Assume 68 Angstroms surface area per lipid head groups, and assume further that the charged lipids are uniformly distributed and immobile. The membrane is in contact with an aqueous solution of NaCl at 25 degrees celcius. The salt concentration is 100mM.

a.) Calculate the areal charge density of the membrane

b.) Calculate the surface potential of the membrane


Homework Equations


area density = derivative of charge?
Electric field and potential equations

The Attempt at a Solution



I am totally stuck and have no idea where to begin. I was first wondering what to model the membrane as? Should I model the bilayer as concentric spheres? I believe if I use concentric spheres, I can find the potential. I am unsure about the charge density; I don't quite understand how to use percentage of heads that are charged/not for this.
 
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