Difference between hydrophobic and hydrophilic amino acids

Hydrophobic and hydrophilic amino acids

What is the difference between hydrophobic and hydrophilic amino acids?

Hydrophilic amino acids are attracted to water and have a polar nature. In contrast, hydrophobic amino acids are repelled by water and are also nonpolar. This explanation is elementary. However, we will elaborate further in the article to better explain the difference between hydrophobic and hydrophilic amino acids. With that being said, do not expect an overly scientific explanation because the chemistry of amino acids is vast and confusing. We will stick to the basics and just the relevant bits for your sanity and ours.

Which amino acids are hydrophilic?

There is a total of 6 hydrophilic amino acids. Hydrophilic amino acids have a polar side chain, making them “water-friendly” they are attracted to water and are water-soluble. Below is a list of the six hydrophilic amino acids.[1]

  • Arginine
  • Asparagine
  • Aspartic Acid
  • Glutamine
  • Glutamic Acid
  • Lysine

Which amino acids are hydrophobic?

There is a total of 8 hydrophobic amino acids. Hydrophobic amino acids are nonpolar in nature, resulting in them repelling water. Hydrophobic amino acids are not soluble in water. If you have ever tried to mix hydrophobic amino acids into a liquid like water, you will see that it clumps on the top of the water and does not mix. Below is a list of all eight of the hydrophobic amino acids.[1]

  • Alanine
  • Cysteine
  • Isoleucine
  • Leucine
  • Valine
  • Methionine
  • Phenylalanine
  • Tryptophan

As you can see, the branched-chain amino acids leucine, isoleucine and valine are all hydrophobic. Branched-chain amino acids are among the most prevalent amino acid supplements, so if you want to take them, you should buy pill or capsule forms. If you buy the powder form of these amino acids, you will save money, but you will not like the taste as these powders will not mix well in liquids.

Which amino acids are neutral?

There are 6 amino acids that are neutral. This neutrality means they are neither hydrophobic nor hydrophilic. These amino acids’ solubility or ability to be mixed in water is somewhere in between hydrophobic and hydrophilic. Below is the list of the six neutral amino acids.[1]

  • Glycine
  • Histidine
  • Proline
  • Serine
  • Tyrosine

What’s the difference between polar and nonpolar amino acids?

Polar amino acids have polarity or a positive charge. In contrast, nonpolar amino acids have no polarity and have a neutral charge. Let’s break down polar vs nonpolar amino acids further.

What are polar amino acids?

As mentioned above, polar amino acids mostly have a positive charge. Polar amino acids are hydrophilic. They are attracted to water, and water is drawn to them. The neutral amino acids can also fall into this polar group. There are three types of polar amino acids: neutral, positively charged, and negatively charged.[2]

What are nonpolar amino acids?

Nonpolar amino acids have no polarity or charge. A carboxylic acid group and an amine group are equally present in these amino acids. The result is a neutral charge on these nonpolar amino acids. Nonpolar amino acids are hydrophobic and repel, and are repelled by water.[3]

The differences between polar and nonpolar amino acids can get technical and confusing. The critical point to remember about polar and nonpolar amino acids is that polar amino acids are hydrophilic and nonpolar amino acids are hydrophobic.

amino acid groups
amino acid groups

How do you know if a protein is hydrophobic or hydrophilic?

By looking at its amino acid composition, you can tell if a protein is hydrophobic or hydrophilic. If the protein has a more significant content of hydrophobic amino acids by weight, the protein would be hydrophobic. The opposite would also be true if your protein had was made up of more hydrophilic amino acids, then it would be a hydrophilic protein. This explanation is elementary and straightforward and does not consider more complex chemistry, but for this article, it is adequate. Another crude and straightforward way to tell if your protein is hydrophobic or hydrophilic is by trying to mix it in water. If your protein mixes easily and completely, you can safely assume it is a hydrophilic protein. If the protein does not mix easily or well, you know it is a hydrophobic protein.

Summary of hydrophobic and hydrophilic amino acids

Most athletes and bodybuilders never even think about the structure or chemistry of the amino acids or protein they ingest every day. However, as you can see from this article, knowing if the amino acids or protein you are consuming is hydrophobic or hydrophilic can help you find a better tasting and mixing supplement. The solubility might not seem like a big deal, but if you plan to consume a supplement multiple times a day, how it tastes and mixes begins to matter. So like we mentioned above, if you plan to take a powder supplement like individual amino acids or a protein powder, check it against the hydrophobic or hydrophilic amino acid list to see if it will mix well. If the supplement powder you are looking at is hydrophobic, you might want to consider buying a pill or capsule form, as it will taste and be easier to take. Another option is to buy the powder but put the powder into capsules yourself.

Any information contained within this article is not intended to be taken as medical advice. You should consult your doctor before starting any exercise or supplement.