Peptide Bonds: Features and Formation

Yazan Hamzeh, Meg Desko
  • Author
    Yazan Hamzeh

    I am an inspiring budding scientist, who currently works at a fertility unit. I graduated with BSc (honors) in Genetic Engineering from Jordan University of Science and Technology, and then pursued an MSc in Clinical Embryology at the University of Oxford where I graduated with merit. During the course of academic endeavors, I found a passion in writing, whether it being scientific writing or blog writing. Therefore, I am so glad to be a part of! I am looking forward to hopefully inspire the many budding students out there.

  • Instructor
    Meg Desko

    Meg has taught college-level science. She holds a Ph.D. in biochemistry.

What is a peptide bond? Learn the types, structure, and formation of the peptide bonds between amino acids. Understand proteins as a polymer of amino acids. Updated: 07/26/2021

Table of Contents


Peptide Bond

Proteins, which are vital to the functionality of all living organisms, are made up of multiple amino acid monomers linked together via peptide bonds. Peptide bonds are chemical covalent bonds linking one amino acid to the other, and they form between a carbon atom of one amino acid and a nitrogen atom of the other amino acid. The end of a protein with a free nitrogen atom is referred to as the N-terminus, while the other end of a protein with a free carbon atom is referred to as the C-terminus.

What type of Bond is Formed Between Amino Acids?

Amino acids are composed of a central carbon atom bonded to a hydrogen atom and a functional R group, which determines the amino acid identity, and a carboxyl group on one side and an amino group on the other. Upon peptide bond formation, the carbonyl group of the first amino acid loses a hydroxyl (OH) and the amino group of the second amino acid loses a hydrogen (H). This process is known as dehydration, and forms a covalent bond between the two amino acids involved, known as the peptide bond, and generates a water molecule in the process.

Formation of a Peptide Bond

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Amino Acids Polymerization

A protein molecule is generally composed of a multitude of amino acids, or peptides, linked together via peptide bonds. The human body makes use of 20 naturally occurring amino acids. Proteins differ in the number and type of amino acids they possess.

Types of Peptides

Protein nomenclature can be dependent on the number of peptides they encompass. For example:

  • Dipeptides: a protein structure that is made of two amino acid residues linked together via one covalent bond. An example of a dipeptide is Aspartame, which is used as a low-calorie sugar substitute commercially.
  • Tripeptides: a protein structure that is made of three amino acid residues linked together via two covalent bonds. An example of a tripeptide is Glutathione, which protects cells from harmful toxins such as free radicals due to to its antioxidant nature.
  • Oligopeptides: a protein structure composed of several amino acid residues organized in small chains. Oligopeptides are typically composed of two to forty amino acid residues. An example of an oligopeptide is Antipain, which is secreted by bacteria and acts as a protein inhibitor.
  • Polypeptides: a large protein structure composed of up to two thousand amino acid residues. Polypeptides are typically referred to as proteins. Common examples of polypeptides include hormones such as insulin and glucagon.

What is a Polymer of Amino Acids?

As explained earlier, a protein is made of a sequence of amino acids linked together via peptide bonds in a process titled polymerization. The order and sequence of amino acids are specific to each protein, which gives rise to the protein's primary structure.

Is Protein A Polymer?

A protein is said to be a polymer of amino acid monomers. The specific order in which amino acids are bonded is crucial to assemble the protein in a particular manner which is necessary for protein function. Upon protein assembly in the cytoplasm, multiple cellular checkpoints occur to ensure the sequence of amino acids is correct. Mutations in the genetic code or DNA, which provides instructions on the assembly of every protein, could cause a change in the protein's primary structure and hence its shape and function. For example, sickle cell disease is brought upon by a change in the DNA sequence which gives rise to coding the valine amino acid instead of glutamine. This results in impairment in beta-globin structure, which is detrimental to red blood cell functions.

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Frequently Asked Questions

How do you identify a peptide bond?

A peptide bond is occurs between the carboxyl group of one amino acid and an amine group with the other amino acid.

How do two amino acids bind?

Two amino acids bind via a peptide bond. The formation of a peptide bond occurs between a carboxyl group of one amino acid and an amine group of the other.

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