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

Proteins and Amino Acids

Organic Chemistry

29. Amino Acids

Proteins and Amino Acids

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4:20 minutes

Problem 32

Textbook Question

What dipeptides would be formed by heating a mixture of valine and N-protected leucine?

Verified step by step guidance

Step 1: Understand the problem. A dipeptide is formed when two amino acids are joined by a peptide bond. In this case, the amino acids are valine (Val) and N-protected leucine (Leu). The N-protection on leucine prevents its amino group from participating in the reaction, so only its carboxyl group can react.

Step 2: Identify the functional groups involved. Valine has both an amino group (-NH₂) and a carboxyl group (-COOH) available for reaction. N-protected leucine has its amino group blocked, leaving only its carboxyl group (-COOH) available for reaction.

Step 3: Determine the possible reaction pathways. The peptide bond can form in two ways: (1) the amino group of valine reacts with the carboxyl group of N-protected leucine, forming Val-Leu (N-protected), or (2) the carboxyl group of valine reacts with the amino group of N-protected leucine, forming Leu-Val (N-protected).

Step 4: Write the chemical structures of the dipeptides. For Val-Leu, the structure will have valine at the N-terminus and N-protected leucine at the C-terminus. For Leu-Val, the structure will have N-protected leucine at the N-terminus and valine at the C-terminus. Use MathML to represent the structures if needed.

Step 5: Conclude that heating the mixture of valine and N-protected leucine can result in the formation of two dipeptides: Val-Leu (N-protected) and Leu-Val (N-protected), depending on the direction of the peptide bond formation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Dipeptides

Dipeptides are organic compounds formed by the condensation of two amino acids, linked by a peptide bond. This bond is created when the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of water. Understanding the structure and formation of dipeptides is essential for predicting the products of amino acid reactions.

Amino Acid Structure

Amino acids are the building blocks of proteins, each consisting of a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group). The side chains determine the properties and identity of the amino acids, such as valine and leucine. Recognizing the specific structures of these amino acids is crucial for understanding how they interact and form dipeptides.

N-protection in Amino Acids

N-protection refers to the modification of the amino group in an amino acid to prevent it from participating in unwanted reactions during peptide synthesis. This is often achieved using protecting groups that can be removed later. In the context of the question, knowing how N-protected leucine behaves when heated with valine is vital for predicting the resulting dipeptides.

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Related Practice

Textbook Question

Predict the products of the following reactions.

(f)

Textbook Question

Show how you would synthesize any of the standard amino acids from each starting material. You may use any necessary reagents.

(c)

Textbook Question

For each compound,

1. name the functional group.

2. show what compound(s) result from complete hydrolysis.

(c)

Textbook Question

a. Calculate the overall yield of bradykinin when the yield for the addition of each amino acid to the chain is 70%.

b. What would be the overall yield of a peptide containing 15 amino acids if the yield for the incorporation of each is 80%

Textbook Question

Proof that an imine was formed between aldolase and its substrate was obtained by using D-fructose-1,6-bisphosphate labeled at the C-2 position with ¹⁴C as the substrate. NaBH₄ was added to the reaction mixture. A radioactive product was isolated from the reaction mixture and hydrolyzed in an acidic solution. Draw the structure of the radioactive product obtained from the acidic solution. (Hint: NaBH₄ reduces an imine linkage.)

Textbook Question

Draw the product obtained when a lysine side chain in a polypeptide reacts with maleic anhydride.

Textbook Question

Draw the tetrapeptide Ala-Thr-Asp-Asn and indicate the peptide bonds.

Multiple Choice

The unique properties of the 20 common amino acids are determined by which of the following?

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