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Are free fatty acids zwitterionic?
Hello,
Are free fatty acids zwitterionic? And if they are, at which pH is the isoelectric point? Is the isoelectric point the same for all fatty acids, regardless of the carbon chain length or saturation/unsaturation?
Thanks
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2 Replies
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Free fatty acids are anionic (in aqueous solutions).
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Hi Pharma
I know it’s been a while, but I’ve done some further digging on this subject. In your answer you stated FFAs are anionic in aqueous solutions. Is that under the assumption that the pH of the aqueous solution is around the neutral pH / pH 7?
I came across this research article titled: “Characterization of the Charged Components and Their Topology on
the Surface of Plant Seed Oil Bodies”.Here’s the link: https://www.jbc.org/article/S0021-9258(19)49582-3/pdf
The article mentioned the following:
“Further decrease of the pH to 5.0 likely protonates the free fatty acids and produces positively charged organelles.” (mentioned in the intro/abstract)
And:
“Further lowering of the pH from 6 to 4 protonates the free fatty acid, which is the only lipid or amino acid residue having a pK of about 5; the now positively charged oil bodies repulse one another, thereby reducing aggregation.” (mentioned on page 8, first paragraph on the right, line 4)
So according to this article free fatty acids get protonated around pH 4-5. Is it then correct to conclude that FFA’s are cationic from pH4-5 and lower? Or am I misinterpreting that piece of information?
Thank you for your help btw!
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