![hydrophobic amino acids with nonpolar side chains hydrophobic amino acids with nonpolar side chains](https://i2.wp.com/cms.jackwestin.com/wp-content/uploads/2020/02/Amino-acid-chart.png)
For example, the hydroxyl group present in tyrosine increase its reactivity and solubility compared to that of phenylalanine.
![hydrophobic amino acids with nonpolar side chains hydrophobic amino acids with nonpolar side chains](https://i.pinimg.com/originals/ca/2e/b5/ca2eb584901d8b3551b61c00eb86247a.jpg)
However, it should be noted that hydrophobicity and hydrophilicity represent a sliding scale and each of the different amino acids can have different physical and chemical properties depending on their structure.
![hydrophobic amino acids with nonpolar side chains hydrophobic amino acids with nonpolar side chains](https://image1.slideserve.com/2192154/amino-acids-with-nonpolar-side-chains-l.jpg)
The aromatic amino acids (phenylalanine, tyrosine, and tryptophan), as their name implies, contain an aromatic functional groups within their structure making them largely nonpolar and hydrophobic due to the high carbon/hydrogen content. As we will see in the next section covering primary structure, proline can significantly alter the 3-dimentional structure of the due to the structural rigidity of the ring structure when it is incorporated into the polypeptide chain and is commonly found in regions of the protein where folds or turns occur. Proline is also classified as an aliphatic amino acid but contains special properties as the hydrocarbon chain has cyclized with the terminal amine creating a unique 5-membered ring structure. The aliphatic amino acids (glycine, alanine, valine, leucine, isoleucine, and proline) typically contain branched hydrocarbon chains with the simplest being glycine to the more complicated structures of leucine and valine. The nonpolar amino acids can largely be subdivided into two more specific classes, the aliphaticamino acids and the aromaticamino acids. Colors indicate specific amino acid classes: Hydrophobic - Green and Yellow, Hydrophilic Polar Uncharged - Orange, Hydrophilic Acidic - Blue, Hydrophilic Basic - Rose.Ĭlick Here for a Downloadable Version of the Amino Acid Chart R-groups are indicated by circled/colored portion of each molecule. The fully protonated structure of an amino acid (at low pH) is shown in Figure \(\PageIndex\): Structure of the 20 Alpha Amino Acids used in Protein Synthesis. They differ from one another only at the R-group position. Within living organisms there are 20 common amino acids used as protein building blocks. In the diagram below, this group is designated as an R-group. In addition to the amine and the carboxylic acid, the alpha carbon is also attached to a hydrogen and one additional group that can vary in size and length. The alpha designation is used to indicate that these two functional groups are separated from one another by one carbon group. As their name implies they contain a carboxylic acid functional group and an amine functional group. The major building block of proteins are called alpha (α) amino acids.