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Phosphodiester Bonds Overview

Yazan Hamzeh, Angela Hartsock
  • 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
    Angela Hartsock

    Angela has taught college microbiology and anatomy & physiology, has a doctoral degree in microbiology, and has worked as a post-doctoral research scholar for Pittsburgh’s National Energy Technology Laboratory.

Understand what a phosphodiester bond is, learn about phosphodiester bond formation, explore the role of phosphodiester bonds in DNA and RNA, and discover its biological importance. Updated: 09/28/2021

Table of Contents


What is a Phosphodiester Bond?

Chemical bonds between atoms and molecules occur in several types and forms. Chemical bonding can occur in the form of ionic bonding, covalent bonding, or metallic bonding. Ionic bonds and metallic bonds occur as a result of electrostatic attraction between oppositely charged atoms or molecules, while covalent bonds occur as a result of atoms sharing a pair of electrons. Covalent bonds are especially abundant in organic molecules and are necessary for the formation of many molecules that make up living cells. An example of these bonds is a phosphodiester bond. What is a phosphodiester bond? It is a covalent bond between sugar and phosphates that is vital for the formation of the cell's nucleic acid content.

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  • 0:00 Intro to Nucleic Acids
  • 1:30 Phosphodiester Bonds
  • 2:37 The Structure of DNA
  • 3:36 Lesson Summary
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Phosphodiester Bond Formation

Phosphodiester bond formation occurs between 2 hydroxyls (OH) groups present in 2 different sugar molecules and a phosphate group. The sugar molecules and phosphate group are found in nucleotides, which are monomers of nucleic acid; nucleotides are composed of a phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogen-containing base. The formation of a phosphodiester bond involves the removal of a water molecule, therefore it is referred to as a condensation reaction. Upon condensation, the nucleotides that form the phosphodiester would now have a sugar-phosphate backbone, which is a structure necessary for nucleic acid structural stability and function. The formation of a phosphodiester bond between nucleotides provides directionality for the resulting nucleic acid strand. This is referred to as the 5'-3' direction, as the nucleic acid would grow from 5' end of one sugar to the 3' end of another sugar.

Phosphodiester Bonds in DNA and RNA

Phosphodiester bonds are vital to maintaining the structural stability of nucleic acids. Nucleic acids can be in the form of deoxyribonucleic acids (DNA) or ribonucleic acid (RNA). DNA and RNA differ in structure, as DNA is a double-stranded ladder-like molecule while RNA is a single-stranded molecule. However, both structures contain the sugar-phosphate backbone that is brought about by phosphodiester bond formation. While a phosphodiester bond in DNA is vital to maintaining its structure, it needs to be easily broken down to facilitate a variety of cellular processes such as DNA error repair. DNA replication occurs prior to cell division, which is highly error-prone. The cell contains enzymes that repair the errors that occur but also need enzymes that are able to break the phosphodiester bond in order for the repair to progress. These enzymes are referred to as phosphodiesterase enzymes and conduct their function via hydrolysis, or the addition of a water molecule.

Research has emphasized the stability of phosphodiester bonds in DNA, and it has been shown that these bonds have a long half-life of 30 million years at room temperature. This suggests that phosphodiester bond hydrolysis is catalyzed and accelerated by enzymes such as phosphodiesterase. On the other hand, research has also shown that this phenomenon differs in RNA. RNA phosphodiester bonds have been shown to be less stable than in DNA, as the half-life of an RNA phosphodiester bond is 120 months under room temperature. This is due to the presence of hydroxyl on the 2' carbon, as the sugar in RNA differs from the one in DNA. This instability is also a result of RNA exhibiting enzyme-like characteristics, which are called ribozymes; ribozymes can cleave the RNA phosphodiester bond.

Phosphodiester Bond Formation

Condensation reactions form phosphodiester bonds.

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Frequently Asked Questions

What is a phosphodiester bond in biology?

A phosphodiester bond is a covalent bond between phosphate and 2 sugars (hydroxyl groups). A covalent bond involves the sharing of a pair of electrons.

Why is a phosphodiester bond important?

A phosphodiester bond is vital for the maintenance of the structural stability of nucleic acids. Nucleic acids are in the form of DNA and RNA and are important for cell structure and function.

How do you identify a phosphodiester bond?

A phosphodiester bond is identified as a bond between 2 sugar hydroxyl groups and a phosphate group. It is found in DNA and RNA.

How is a phosphodiester bond formed in DNA?

A phosphodiester bond is formed between two nucleotides to form the sugar-phosphate backbone of DNA. This reaction occurs as a condensation reaction, where a water molecule is removed.

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