Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

29. Amino Acids

Polar Amino Acids

Organic Chemistry

29. Amino Acids

Polar Amino Acids

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Multiple Choice

Which of the following amino acids will have a net positive charge at physiological pH?

The figure illustrates the structure of a molecule. A 2-carbon alkane chain is depicted as a line structure using 1 line. C 1 is double bonded to O below and single bonded to N H 2 on the lower left. C 2 is dash bonded above to C 1 of a second 2-carbon alkane chain depicted as a line structure using 1 line. C 1 of the second 2-carbon alkane chain is single bonded to N H 2 on the upper left. C 2 of the second 2-carbon alkane chain is double bonded to O above and single bonded to O H on the lower right.

The figure illustrates the structure of a molecule. A 3-carbon alkane chain is depicted as a line structure using 2 zigzag lines. C 1 is double bonded to O on the lower right and single bonded to O H on the lower left. C 3 is dash bonded above to C 1 of a 2-carbon alkane chain depicted as a line structure using 1 line. C 1 of the 2-carbon alkane chain is single bonded to N H 2 on the upper left. C 2 of the 2-carbon alkane chain is double bonded to O above and single bonded to O H on the lower right.

The figure illustrates the structure of a molecule. A 2-carbon alkane chain is depicted as a line structure using 1 line. C 1 is single bonded to N H 2 on the upper left and dash bonded to C H 2 below in the form of a dashed line. C H 2 is single bonded to S H on the lower right. C 2 is double bonded to O above and single bonded to O H on the lower right.

The figure illustrates the structure of a molecule. A 4-carbon alkane chain is depicted as a line structure using 3 zigzag lines. C 1 is single bonded to N H 2 below. C 4 is dash bonded above to C 1 of a 2-carbon alkane chain depicted as a line structure using 1 line. C 1 of the 2-carbon alkane chain is single bonded to N H 2 on the upper left. C 2 of the 2-carbon alkane chain is double bonded to O above and single bonded to O H on the lower right.

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Verified step by step guidance

Identify the amino acids shown in the images. The first image is glutamine, the second is aspartic acid, the third is cysteine, and the fourth is lysine.

Understand the concept of physiological pH, which is approximately 7.4. At this pH, amino acids can exist in different ionization states depending on their side chains.

Consider the side chains of each amino acid. Glutamine has a neutral amide group, aspartic acid has a carboxylic acid group, cysteine has a thiol group, and lysine has an amine group.

Determine the ionization state of each amino acid at physiological pH. Amino acids with acidic side chains (like aspartic acid) will be deprotonated and negatively charged, while those with basic side chains (like lysine) will be protonated and positively charged.

Conclude that lysine, with its basic amine side chain, will have a net positive charge at physiological pH due to the protonation of its side chain amine group.