Why tyrosine is hydrophobic

This should mean that Tyrosine and Tryptophan are polar, so why are they non-polar, even with an electronegative atom in their side chains? Unlike that in organic chemistry, polar and non-polar compounds determination is done differently in biochemistry, probably because most biochemical reactions are done in aqueous medium. Therefore, the classification of them as polar and non-polar is somewhat different from source to source.

In general, amino acids, which can make hydrogen bonding in aqueous solutions are called polar, and ones repel from water are non-polar. According to Ref. All 10 non-polar amino acids are hydrophobic and 10 polar amino acids are hydrophilic.

Polar amino acid residues have a tendency to be on the outside of a protein, due to the hydrophilic properties of the side chain Ref. Keep in mind that tryptophan has indole function, but its lone pair of nitrogen is involved in the aromatic system. Thus, it make only weal H-bonding, which are not good enough to categorize as "polar.

Tryptophan is less hydrophobic than phenylalanine and as a whole tryptophan is considered non polar although it has an additional N-H group at its side chain..

Look at the side chain of tryptophan which is more hydrophobic and large so if a tiny part N-H in its side chain is polar than still it can not influence the hydrophobicity of the entire side chain which is so large..

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Create a free Team What is Teams? Learn more. On the basis of both the transition temperature scale and the heat of transition, the hydroxylated tyrosine appears less hydrophobic than glycine.

Abstract Relative hydrophobicities of aromatic amino acid residues are investigated by using differential scanning calorimetry DSC on 10 synthetic copolypentapeptides of poly VPGVG of elastin. Publication types Research Support, U. Gov't, Non-P. For example, even phenylalanine only has an aromatic ring, tyrosine is more soluble than it in water.

In contrast, tyrosine has been found through x-ray crystallography to reside in a hydrophobic environment regardless of it hydroxyl group. Based on what the textbooks and online resources use as their criteria will determine if they characterize tyrosine as polar or non-polar. For academic purposes, I would go by what your textbook characterizes it as.

For research purposes, know that tyrosine has this unique dual property that can be exploited in experiments.