It is a good idea to have a general idea of the structure of the different amino acids and to be able to recognize them as amino acids. You are not expected to memorize these structures. Often I say the name of amino acids and not all students understand that I am talking about an amino acid. Each amino acid differs only by its side group, which is circled in red in each figure below. Also, the more familiar you become with chemical structures, the more prepared you will be for later classes.
 Histidine1 |
 Isoleucine2 |
 Leucine3 |
 Lysine4 |
 Methionine5 |
 Phenylalanine6 |
 Threonine7 |
 Tryptophan8 |
 Valine9 |
Figure 2.261 Essential amino acids
You may hear someone talk about the branch chain amino acids, which are all essential amino acids, but they are singled out in the figure below.
Figure 2.262 Branched chain amino acids; Valine, Leucine, Isoleucine
 Arginine10 |
 Cysteine11 |
 Glutamine12 |
 Glycine13 |
 Proline14 |
 Tyrosine15 |
Figure 2.263 Conditionally essential amino acids
 Alanine16 |
 Asparagine17 |
 Aspartate (aspartic acid)18 |
 Glutamate (glutamic acid)19 |
 Serine20 |
Figure 2.264 Nonessential amino acids
References & Links
1. https://en.wikipedia.org/wiki/Histidine#/media/File:Histidin_-_Histidine.svg
2. https://en.wikipedia.org/wiki/Isoleucine#/media/File:L-Isoleucin_-_L-Isoleucine.svg
3. https://en.wikipedia.org/wiki/Leucine#/media/File:Leucine_Nonionic.svg
4. https://en.wikipedia.org/wiki/Lysine#/media/File:L-lysine-monocation-2D-skeletal.png
5. https://en.wikipedia.org/wiki/Methionine#/media/File:Methionin_-_Methionine.svg
6. https://en.wikipedia.org/wiki/Phenylalanine#/media/File:L-Phenylalanin_-_L-Phenylalanine.svg
7. https://en.wikipedia.org/wiki/Threonine#/media/File:Threonineasdf.png
8. https://en.wikipedia.org/wiki/Tryptophan#/media/File:L-Tryptophan_-_L-Tryptophan.svg
9. https://en.wikipedia.org/wiki/Valine#/media/File:ValinenotatpH7.4.png
10. https://en.wikipedia.org/wiki/Arginine#/media/File:Arginin_-_Arginine.svg
11. https://en.wikipedia.org/wiki/Cysteine#/media/File:L-Cystein_-_L-Cysteine.svg
12. https://en.wikipedia.org/wiki/Glutamine#/media/File:L-Glutamin_-_L-Glutamine.svg
13. https://en.wikipedia.org/wiki/Glycine#/media/File:Glycin_-_Glycine.svg
14. https://en.wikipedia.org/wiki/Proline#/media/File:Prolin_-_Proline.svg
15. https://en.wikipedia.org/wiki/Tyrosine#/media/File:L-Tyrosin_-_L-Tyrosine.svg
16. https://en.wikipedia.org/wiki/Alanine#/media/File:L-Alanin_-_L-Alanine.svg
17. https://en.wikipedia.org/wiki/Asparagine#/media/File:L-Asparagin_-_L-Asparagine.svg
18. https://en.wikipedia.org/wiki/Aspartic_acid#/media/File:Aspartic_Acidph.png
19. https://en.wikipedia.org/wiki/Glutamic_acid#/media/File:Glutamic_Non-ionic.png
20. https://en.wikipedia.org/wiki/Serine#/media/File:L-Serin_-_L-Serine.svg
