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Phosphodiester Bond: Formation & Overview

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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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Lesson Transcript
Instructor: Angela Hartsock

Angela has taught college Microbiology and has a doctoral degree in Microbiology.

DNA molecules are held together by different types of bonds. In this lesson, you'll learn about the role of phosphodiester bonds in the structure of DNA.

Intro to Nucleic Acids

DNA and RNA are the building blocks of life. These molecules contain all the information required to build a functioning organism, like a human body. DNA and RNA contain the information required to build cells, assemble organs, grow, and reproduce. DNA, deoxyribonucleic acid, and RNA, ribonucleic acid, are both nucleic acids. Nucleic acids are polynucleotides, where 'poly' means multiple and refers to many nucleotides linked together by chemical bonds. All nucleotides are made up the same basic components: a sugar, a phosphate, and a nitrogenous base.

DNA nucleotides are made of a sugar called deoxyribose, a nitrogenous base, and a phosphate. The DNA nitrogenous bases are the famous A (adenine), G (guanine), C (cytosine), and T (thymine).

RNA nucleotides are made of a sugar called ribose, a nitrogenous base, and a phosphate. The RNA nitrogenous bases are A (adenine), G (guanine), C (cytosine), with the special U (uracil) replacing the thymine from DNA.

As you can see, DNA and RNA share some basic components so their overall structure is very similar. The DNA and RNA polynucleotides are built using a very simple, but very important, bond: the phosphodiester bond.

DNA & RNA
DNARNAsidebyside

Phosphodiester Bonds

Let's breakdown the term:

'Phospho-' refers to the element phosphorus, '-di-' means two, and '-ester' refers to a specific type of chemical bond that includes a single atom bound to two oxygen atoms. So, a phosphodiester bond is a phosphorus atom involved in two ester bonds. That may sound complicated, but it really is simple once you see it in action. Let's look closer at the structure of DNA.

Phosphodiester bond
DNAphospho

DNA nucleotides are linked by having a phosphate shared between two deoxyribose sugars on adjacent nucleotides. Phosphate is a very simple molecule made up of a phosphorus atom bonded to four oxygen atoms. This molecule is reactive, meaning that it wants to be bonded to another molecule. Deoxyribose is a sugar that has two free hydroxyl groups (-OH) that are also reactive. These -OH groups are important because it is here that the phosphodiester bonds form, linking each deoxyribose to the phosphorus. These are the two ester linkages. So each deoxyribose has two available -OH groups and can bind to two phosphates creating a chain, aka the backbone of the DNA.

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