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