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Organic Compounds: Nucleic Acids

Organic Compounds: Nucleic Acids

Author: Amanda Soderlind

Identify the elements of nucleic acids.

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Organic Molecules: Nucleic Acids

Source: All images created by Amanda Soderlind

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In this lesson we are going to discuss the structure and function of nucleic acids, as well as the role they play in our bodies. So first of all, nucleic acids are organic compounds. And what this means is that they contain the element carbon.

And the two types of nucleic acids we're going to talk about today are DNA and RNA. So we're going to start by talking about nucleotides. And nucleotides are the building blocks of nucleic acids. They are what compose nucleic acids, DNA and RNA.

So I just have a simple drawing of a nucleotide here, just so we can discuss the structure. So nucleotides are made up of a sugar, a phosphate group, and a nitrogen base. So all nucleotides are going to have this similar structure.

There is going to be some difference between certain nucleotides, however. And we'll get into that when we discuss the structure of DNA and RNA a little bit more. But what you need to know is that nucleotides are the building blocks of nucleic acids. And they contain a phosphate group, a sugar, and a nitrogen base.

So we're going to start by discussing DNA. So right here I kind of have the structure of DNA. And DNA is described as being a double helix. So if you think about it, it's kind of like a ladder that's been twisted. And the rungs of the ladder are composed of the nitrogen bases. So you'll remember the structure of the nucleotides we have here, the nitrogen bases that we have for DNA are adenine, thymine, cytosine, and guanine.

So DNA has four nitrogen bases, adenine, thymine, cytosine, and guanine. And in the structure of DNA, the way that the nitrogen bases pair up is very specific. Adenine will always pair up with thymine. And cytosine will always pair up with guanine.

So if you take a look here, you can kind of see where the nucleotides are in the DNA structure, and how that allows DNA to look like it does. So we have our phosphate group here. Our sugar for DNA is deoxyribose sugar, so that type of sugar is specific to DNA. So phosphate group, deoxyribose sugar, and our nitrogen base. And again, if this nitrogen base were adenine, for example, this nitrogen base would be thymine.

And they're bonded together here by a hydrogen bond. So it's a hydrogen bond that holds them together. And again, if this was cytosine, it would be bonded always to guanine, and again, held together by a hydrogen bond.

So DNA you might have heard before has a phosphate-sugar backbone. It's referred to having a phosphate-sugar backbone. So you'll notice right here we have our phosphates and our sugar making the outer part of the double helix. And then the rungs of the ladder, if you will, are made up of the nitrogen bases, bonded by hydrogen bonds.

So this is a little bit about the structure of DNA. And so you'll notice also DNA is double-stranded. And this varies from RNA. So DNA is different than RNA in the fact that it's double-stranded and it has different bases, as well as its sugar is a deoxyribose.

So these are the characteristics of DNA. It's double-stranded. It has a deoxyribose sugar in its nucleotide. And its nitrogen bases are adenine, thymine, cytosine, and guanine.

So we take a look at RNA-- we're going to compare RNA to DNA a little bit here. RNA, rather than being double-stranded, is single-stranded. So it doesn't have the same structure as RNA does. It's shown as a single strand here. The sugar in RNA, rather than being a deoxyribose sugar, is just a ribose sugar. So in the nucleotides of RNA, the sugar would be a ribose sugar.

The nitrogen bases also vary a little bit in RNA as well. Rather than having adenine, thymine, cytosine, and guanine, it has adenine, uracil, cytosine, and guanine. So adenine, uracil, cytosine, guanine. So the nitrogen bases vary a little bit as well. It doesn't have thymine. Instead it has uracil.

So in our bodies, DNA contains all of our genetic information. All of our genes, all of the information about who we are is contained in our DNA, whereas RNA does carry genetic information. But the genetic information it carries helps to build proteins for our body.

So this has been an overview on the structure and function of nucleic acids, and a comparison of DNA versus RNA.

Terms to Know

​Deoxyribonucleic acid; a nucleic acid that contains all the genetic information of an organism.

Nucleic Acid

An organic compound composed of nucleotides; Includes DNA and RNA.


The building blocks of nucleic acids composed of a sugar, a phosphate group, and a nitrogenous base.


Ribonucleic acid; a nucleic acid that helps protein in cells.