So once and for all, are these AA's hydrophobic or hydrophilic?

[swollcat]

Are the polar, uncharged amino acids such as: serine, tyrosine, cysteine, etc. hydrophobic or hydrophilic? I have seen them labeled as either or in multiple reputable sources. I want to say they're hydrophilic because come on now, serine and tyrosine can clearly H bond with their hydroxyl groups.

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[bee17]

I've always learned them as hydrophilic, but I'm no chemistry expert.

 

[GoljansRightBicep]

Are the polar, uncharged amino acids such as: serine, tyrosine, cysteine, etc. hydrophobic or hydrophilic? I have seen them labeled as either or in multiple reputable sources. I want to say they're hydrophilic because come on now, serine and tyrosine can clearly H bond with their hydroxyl groups.

I've never seen Ser or Cys labeled as anything other than hydrophilic. Ever.

Tyr is hydrophilic according to my biochem professor and Garret and Grisham Biochemistry, for what it's worth.

 

[kingtal0n]

You are going to have to decide for yourself given the conditions presented. I can imagine there will be times when, the designers of the test will know that these amino acids give this sort of trouble. So they will likely present you with a question that tests to see if you can imagine them doing one or both activities- behaving perhaps, as an amino acid in the pocket of an enzyme, where it will require the aromatic of tyrosine, and expecting you to know that this was intended. And perhaps there may be an instance, where upon showing you a picture of tyrosine making an hydrophilic interaction with another atom, it may ask a question related to this situation, such as, would this be an ideal situation, or which other amino acid could serve the same function. If you are stuck on the idea of tyrosine being hydrophobic you might mentally associate the other hydrophobic amino acids as related and choose one.

 

[Jiller1994]

Had a question asking me where tyrosine and phenylalanine would be placed on an enzyme- near active site or outside. I answered phenyl on inside and tyrosine on outside and they said that tyrosine belonged inside because it's not "polar enough" more or less. Was thoroughly confused at that point

 

[premedjunkie_11]

From what I've seen on practice tests, Tyrosine is SLIGHTLY polar due to the hydroxyl, but because of the aromatic ring, it is MORE nonpolar than polar so I would say it's safe to call it nonpolar if ever asked about it.

 

[swollcat]

thanks for the info guys. actually, I think its polar, but its definitely not hydrophilic. Apparently its more along the lines of polar, but NEUTRAL. Anyone care to refute this?