Learn about Peptide Bond Features

Multiple molecules and compounds are responsible for the healthy functioning of the human body. One of the main ones is protein, for which peptide bonds are highly responsible. 

Peptide bonds are covalent bonds that occur between two different amino acid molecules. In living organisms, the peptide bonds combine and together form a long amino acid chain or the complex protein molecule. Proteins are valuable for living organisms since they provide structural support, improve strength, and work as a catalyst for different biological reactions.

There are multiple such beneficial features of peptides; learn about them in this article.

Peptide- An Overview 

A peptide bond is a short-chain chemical bond between two different amino acid molecules. When considering the description of a peptide bond, it is important to mention that it forms when the amino group in one molecule reacts with another molecule’s carboxyl group. 

Then, it releases the H2O molecule. When a peptide mixes together with other such bonds, they form protein. Typically, the quantity of amino acids noticeable within each peptide ranges between two to fifty amino acids. 

The reaction between the amino acids is condensation-based or dehydration synthesis. Here, the CO-NH bond that occurs becomes the peptide bond. Plus, the molecule that the reaction creates is known as an amide. 

In proteins, a peptide group or an amide group refers to the four-atom-centric functional group, i.e., C(=O)NH. In PNA, peptide bonds hold the amino acid chains together, also called proteins or polypeptides. 

Types of Peptide Bond 

Before understanding the features of peptides, you must know the types available. 

Dipeptide bond

This type of peptide bond involves two amino acid molecules. The connection is called dipeptide linkage or bond. 

Oligopeptide bond 

If there are four or even ten amino acid molecules, they form the peptide named oligopeptide. Therefore, the linkage is referred to as an oligopeptide bond. 

Tripeptide bond 

In this linkage-type, three amino acids join together. The peptides here are called tripeptides. 

Polypeptide bond 

Peptide bonds with 10-50 amino acid residues are called polypeptide bonds. Bonds with over 50 amino acid molecules or residues are proteins. 

Peptide Bond Features 

There are particular features of peptides that are important to consider when trying to understand their performance. 

• The structure of the peptide bond is planar and rigid. 

• Peptide bonds are essentially covalent bonds that occur between one amino acid’s α-Carboxyl group and another molecule’s α-amino group. 

• The atoms here stand as Cα-C-N-Cα. 

• The bonds contribute to the formation of protein polymers or polypeptide chain polymers. 

• Peptide bonds have a partial double bond character. 

• This bond is a fundamental base in different biological functions and reactions within living organisms. 

• The peptide bond has a coplanar nature. Therefore, there is partial sharing or resonance of two-electron pairs between amide nitrogen and carbonyl oxygen. 

• Peptide bond formation takes a lot of energy. It comes from ATP. 

• One of the main features of peptide bonds is that it stays stable at normal temperature. However, exposure to high 110°C or more temperatures for 48 hours can harm the peptide bond. 

• The 4 atoms that form the structure of peptide bonds, i.e., N, C, O, and H, are present in one single place. The placement shows the carboxyl group’s oxygen atom trans to the amide nitrogen group’s hydrogen atom.

Formation of Peptide Bond 

The peptide bond occurs via dehydration synthesis reaction at the molecular level. When oxygen and two hydrogens are ousted from molecules, two amino acids can satisfactorily bond with each other. 

One of the amino acid molecules gives a carboxyl group into the reaction. That causes a loss of the hydroxyl group inside the reaction and a hydrogen loss in the other amino acid’s amino group. In the position of the missing hydroxyl group, the nitrogen gets into place. This creates the peptide bond. 

Another name for peptide bonds is substituted amide linkages because of this formation sequence. Since the amino acids have lost many atoms, they are called residues. They form a covalent bond together.

Peptide Bond Structure 

The features of peptides are heavily related to the bond’s structure. To understand the former, it is important to note how the structure of peptide bonds forms. 

• Peptide bonds happen between two or more amino acid residues through condensation reaction after removing oxygen and hydrogen. 

• The oxygen and carbonyl carbon double bond have a compact structure, which results in stable resonance structures. 

• The bond holds a double bond character since the alpha-carboxyl group in one amino acid connects to the alpha-amino group in another amino acid. 

• The nitrogen-carbon bond has a shorter structure than carbon-nitrogen single bonds. This is because the peptide chain occurs with CO-NH atoms. Thus, they are planar and rigid, but free rotation can occur around the peptide bond. 

Conclusion

The main features of peptides revolve around connecting the 20 amino acid types that play different roles in maintaining human health. The peptide bonds can form different bonds, and the protein-based peptide groups create the peptide backbone in protein molecules. 

It is important to understand the features and characteristics of the peptide bond and how it is formed. The structure of the peptide bonds is planar and rigid but relatively stable due to the four-atom functional group formation.