Biochemistry: Reactions of amino acids (Part-1)

Summary

This video explores the chemical reactions of amino acids, focusing on those involving both the amino and carboxylic groups. It covers salt formation, peptide bond synthesis, ester and amino acyl chloride formation, decarboxylation, and amide formation. The explanation includes laboratory synthesis techniques and the reactions' underlying mechanics.

Takeaways

• 🧬 Amino acids are organic biomolecules with two oppositely charged functional groups, an amino group and a carboxylic group, attached to the same carbon atom.
• 🌐 Amino acids exist in a zwitterion form, where the amino group is protonated and the carboxylic group is deprotonated.
• 🔗 The chemical reactions of amino acids can involve both the amino and carboxylic groups or be due to one group alone.
• 🧂 Salt formation is a reaction where amino acids react with acids or bases to form salts, such as the chloride salt with hydrochloric acid.
• 🤝 Peptide bond formation is a key reaction involving both the amino and carboxylic groups of different amino acids, leading to the formation of proteins.
• 🧪 Laboratory synthesis of peptide bonds involves the use of phosgene to create an active residue that polymerizes to form peptide chains.
• 🍾 Ester formation is a reaction where amino acids react with alcohol in the presence of dry HCl to form esters, which can be reduced to alcohols.
• 🧪 Amino acyl chlorides are formed by acetylating and then treating amino acids with PCl5, followed by removal of the acetyl group with HCl.
• ♨️ Decarboxylation is a reaction where amino acids lose carbon dioxide upon heating with barium hydroxide or diphenylamine, resulting in amines.
• 🍀 Amide formation involves treating amino acid esters with ammonia to produce amides, as demonstrated with the preparation from amino acid esters.
• 📚 The video promises a follow-up to explain reactions occurring exclusively due to the involvement of the amino group of amino acids.

Q & A

What are amino acids and what makes them unique?

Amino acids are organic biomolecules that contain two oppositely charged functional groups, an amino group and a carboxylic group, covalently bonded to the same carbon atom. They are unique because they can participate in various chemical reactions due to these functional groups.

What is the significance of the amino group and carboxylic group in amino acids?

The amino group is positively charged and the carboxylic group is negatively charged. These groups are significant as they allow amino acids to engage in various chemical reactions, including salt formation, peptide bond formation, and others.

What is the zwitterion form of an amino acid?

The zwitterion form is when the amino group gets protonated and the carboxylic group gets deprotonated, resulting in a molecule with both positive and negative charges.

How do amino acids form salts with acids and bases?

Amino acids form salts when they react with acids like hydrochloric acid to form chloride salts, or with bases like sodium hydroxide to form sodium salts, with the loss of a water molecule.

What is a peptide bond and how is it theoretically formed?

A peptide bond is a linkage formed between the amino group of one amino acid and the carboxylic group of another. Theoretically, it is formed when two amino acids fuse and their respective functional groups react with each other.

Can you describe the laboratory synthesis of a peptide bond?

In the laboratory, an amino acid is heated with phosgene to yield an active residue, which polymerizes to form a peptide chain. The active residues react with each other to form the peptide bond.

What is the purpose of the ester formation reaction in amino acids?

Ester formation is a reaction where an amino acid reacts with an alcohol in the presence of dry HCl to form an ester. This reaction is used to study and modify the properties of amino acids.

How are amino acyl chlorides formed from amino acids?

Amino acyl chlorides are formed by first acetylating the amino acid for protection, then treating it with PCl5, and finally removing the acetyl group with HCl to yield the amino acyl chloride.

What is decarboxylation and how does it relate to amino acids?

Decarboxylation is a reaction where an amino acid, when heated in the presence of barium hydroxide or diphenylamine, loses carbon dioxide and forms an amine. For example, histidine decarboxylates to form histamine.

How can amino acid amides be prepared?

Amino acid amides can be prepared by treating amino acid esters with alcoholic or anhydrous ammonia, which yields the corresponding amino acid amide.

What will be discussed in the next video by the same channel?

The next video will explain the reactions of amino acids that occur exclusively due to the involvement of the amino group.