Amino acids are categorized based on the characteristics of their R groups attached to the alpha carbon, leading to classifications as non-polar, polar, or charged amino acids. Charged amino acids possess an overall positive or negative charge, while non-polar amino acids are hydrophobic, meaning they do not interact well with water.
To remember the non-polar amino acids, a mnemonic device can be used: "Gav Tripp Fell Limping." This phrase helps recall the specific amino acids classified as non-polar. The first part, "GAV," stands for Glycine (Gly), Alanine (Ala), and Valine (Val). Glycine is the simplest amino acid with a hydrogen as its R group. Alanine has a methyl group, making it slightly larger, while Valine features an isopropyl group, further increasing its size.
The next segment, "Tripp," refers to Tryptophan (Trp), which is larger due to its complex ring structure, despite having an NH group that is outnumbered by carbon atoms in its benzene ring. Following this, "Fell" represents Phenylalanine (Phe), which is similar to Tryptophan but has a simpler structure with a benzene ring connected to a CH2 group.
The final part, "Limping," encompasses Leucine (Leu), Isoleucine (Ile), Methionine (Met), and Proline (Pro). Leucine is akin to Valine but includes an additional CH2 group. Isoleucine has a more complex R group with four carbons forming a sec-butyl structure. Methionine is distinctive due to its sulfur-containing side chain, while Proline is unique as its R group forms a ring with the amino group, resembling the letter "P."
In summary, understanding the classification of amino acids, particularly the non-polar group, is essential for grasping their biochemical roles and interactions. The mnemonic "Gav Tripp Fell Limping" serves as an effective tool for recalling these amino acids and their structures.