Question

Draw the structures of the dipeptides that can be formed from the reaction between the amino acids glycine and alanine

Short answer

The dipeptides formed are Gly-Ala: NH2-CH2-CO-NH-CH(CH3)-COOH and Ala-Gly: NH2-CH(CH3)-CO-NH-CH2-COOH.

Step-by-step solution

Identify the Amino Acids

The amino acids involved in this reaction are glycine (Gly) and alanine (Ala). Glycine has the structure NH2-CH2-COOH, with no side chain. Alanine has the structure NH2-CH(CH3)-COOH, with a methyl group (-CH3) as its side chain.

Understand Dipeptide Formation

A dipeptide is formed by a condensation reaction between the amino group of one amino acid and the carboxyl group of another. This reaction releases a molecule of water (H2O) and forms a peptide bond (C-N bond).

Form Gly-Ala Dipeptide

To form the Gly-Ala dipeptide, the carboxyl group of glycine loses an OH and the amino group of alanine loses an H, forming a peptide bond NH2-CH2-CO-NH-CH(CH3)-COOH.

Form Ala-Gly Dipeptide

To form the Ala-Gly dipeptide, the carboxyl group of alanine loses an OH and the amino group of glycine loses an H, resulting in a peptide bond NH2-CH(CH3)-CO-NH-CH2-COOH.

Verify the Structures

Check that each dipeptide has a correct peptide bond formation. Gly-Ala: NH2-CH2-CO-NH-CH(CH3)-COOH, and Ala-Gly: NH2-CH(CH3)-CO-NH-CH2-COOH. Both structures should include one peptide bond, connecting the nitrogen of one amino acid to the carbonyl carbon of the other.

Key concepts

Amino Acids

Amino acids are the building blocks of proteins. They play a crucial role in many biological processes. Every amino acid has a basic structure consisting of:
\( \text{NH}_2 \) group (amino group), \( \text{COOH} \) group (carboxyl group), a hydrogen atom, and an R group (side chain).
The R group varies among amino acids, determining their characteristics and functions in proteins.Key Functions:

• Serve as precursors for biosynthesis of molecules like hormones and neurotransmitters.
• Act as intermediates in metabolic pathways.
• Help in protein synthesis, forming the structural elements of cells.

Amino acids link together to form peptides and proteins, each holding importance in biological processes.

Peptide Bond

A peptide bond is a type of covalent chemical bond. It forms during the reaction between amino acids. When the amino group of one amino acid reacts with the carboxyl group of another, a water molecule (\( \text{H}_2\text{O} \)) is released.
This reaction, known as a condensation reaction, creates the peptide bond, represented as -C(=O)-NH-.Importance of Peptide Bonds:

• Essential for forming polypeptide chains, which then fold into functional proteins.
• Provide structural stability to proteins.
• Protect the protein's structure against denaturation.

Understanding peptide bonds helps grasp how proteins are formed and function, revealing crucial insights into biological activities.

Glycine

Glycine is the simplest amino acid, with the chemical formula \( \text{NH}_2\text{-CH}_2\text{-COOH} \).
This amino acid lacks a side chain (R group), making it unique among its peers. Glycine is often found in proteins and enzymes, contributing to their structure and functioning.Properties of Glycine:

• Aliphatic and non-polar, due to its simple structure.
• The smallest amino acid, allowing flexibility in proteins.
• Acts as an inhibitory neurotransmitter in the central nervous system.

By understanding glycine's role, one appreciates how it supports the structure and function of diverse proteins in living organisms.

Alanine

Alanine is a common amino acid with the structure \( \text{NH}_2\text{-CH(CH}_3\text{)-COOH} \).
It features a methyl group (-CH3) as its side chain. Alanine is widespread in a majority of proteins and is known for its ability to be converted into glucose by the liver.Characteristics of Alanine:

• Non-polar and hydrophobic, due to its alkyl group.
• Involved in glucose metabolism and energy production.
• Key player in the alanine cycle, linking muscle and liver metabolism.

Recognizing the significance of alanine aids in understanding energy transfer and storage processes within cells. Alanine's interplay in metabolic pathways is vital for maintaining energy balance in the body.