Which of the Following Could Be a Nucleotide of Dna

Which of the Following Could Be a Nucleotide of Dna

What is a Nucleotide?

Deoxyribonucleic acid, fondly known as Deoxyribonucleic acid, is a molecule in the shape of a double helix, which is responsible for storing genetic information in the cells of all living organisms. Most people know or should know this. But what is Dna made of exactly?

Prototype Source: Wikimedia Commons

Figure i: The double-helix of the Dna

Dna, and other nucleic acids such as RNA, are made up of nucleotides. Nucleotides are the building blocks of Dna and RNA. The structure ofDNA’s can be visualized or thought of like a ladder. If we continue with this illustration, each “pace or rung” of this ladder is fabricated up of a cord of
nucleotides, in a very specific and controlled order. Each nucleotide, in plough, is fabricated upward of a
nitrogenous base of operations, a
pentose sugar,
and a
phosphate. InFigure 2, the nitrogenous base is enclosed in the ruby-red square on the correct, while the phosphate is enclosed in the blue foursquare on the left. The residual of the molecule forms the pentose saccharide. This detail molecule is adenine; we will observe out more about this later.


Image Source: Wikimedia Commons

Figure ii: The chemical assembly of the three parts of the nucleotide, the phosphate (blue box), nitrogenous base (red box) and the pentose saccharide. This particular nucleotide is adenine

The associates of nucleotides (i) differentiates them from nucleosides, which practice not contain a phosphate group (in the blueish box); (2) allows the nucleotide to connect to other nucleotides when the nitrogenous base forms a hydrogen bond with another nucleotide’s nitrogenous base of operations; as well every bit (3) allows the phosphate to class a phosphodiester bond with another nucleotide’s pentose saccharide. This results in a complex double-stranded “string or ladder”, as seen in figure1.This is the basis of the form of Deoxyribonucleic acid.

The Nitrogenous Base

The discussion “nucleotide” was beginning coined by P.A. Levene, who observed that Dna independent four similar building blocks, in roughly equal amounts. These edifice blocks are what nosotros at present know as the
nitrogenous bases
establish in Dna and RNA.

A nitrogenous base is a molecule containing nitrogen, with the chemical properties of a base due to a pair of electrons on the nitrogen atom. These nitrogenous bases are Adenine (A), Cytosine (C) and Guanine (K) which are found in both RNA and DNA and so Thymine (T) which is only found in Dna and Uracil (U), which takes the place of Thymine in RNA.

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Nitrogenous bases can be farther classified as
purines. Cytosine, uracil and thymine are all pyrimidines. That is, their molecular structure comprises a nitrogenous base in the form of a
six-member single ring. Guanine and adenine, on the other hand, are purines. These contain a nitrogenous base in the form of a
nine-member double ring. In short, pyrimidines have only i ring while purines accept ii (effigy three).

Now that you get the general idea of purines versus pyrimidines let’s speak biochemistry. A purine is a heterocyclic effluvious organic compound that comprises of a pyrimidine ring that is joined to an imidazole ring. The next logical question, of form, becomes“what then is a pyrimidine, biochemically speaking”? Well, pyrimidines are a class of nitrogenous compounds that have only one heterocyclic ring.


Image Source: Wikimedia Commons

Effigy 3: Chemic structure of purines (A, Thou) and pyrimidines (C, T/U)

Nitrogenous bases form
base pairswith each other in DNA: Adenine always pairs with thymine; guanine is always bonded to cytosine. If you were paying attention, you’ll notice that this means that a pyrimidine is always bonded to a purine. The bond formed is a hydrogen bond, and is responsible for the rungs formed in the Dna “ladder”.This architecture is very important for the perfect structure of the Deoxyribonucleic acid molecule. Otherwise, there would be bumps and crevices on the molecule. This wouldn’t practice at all considering the very careful packaging, unwinding, and winding of the DNA would be a mess with some more difficult to maintain than others.

This pairing is, therefore, crucial for genetic part, and is the foundation for Dna replication and gene expression. The gild in which base pairs appear determines the performance of your physiology. In poly peptide synthesis, for example, the code is read in triplicates where three bases lawmaking for a item amino acid. Deletions and insertions of nucleotides in this situation tin pb to a complete frame shift disrupting the synthesis of the protein in question. Substitutions can also be problematic although less and so, every bit they may alter the identity of an amino acid in the protein code.

The Phosphate Group

The phosphate group (PO4) is what differentiates a nucleotide from a nucleoside. This add-on changes the nucleoside from a base to an acid. These phosphate groups are of import, equally they form phosphodiester bonds with the pentose sugars to create the sides of the DNA “ladder”. This is critical, equally the hydrogen bonds which join the nitrogenous bases are not very strong. These sides of the ladder are hydrophilic (attracted to water), allowing the DNA molecule to bond with water.

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What are Nucleoside Diphosphates and Triphosphates?

You know that a nucleotide is differentiated from a nucleoside by one phosphate group. Accordingly, a nucleotide can also be a
nucleoside monophosphate(figure 4). If more phosphates bond to the nucleotide (nucleoside monophosphate) information technology tin become a nucleoside diphosphate (if two phosphates bond), or a nucleoside triphosphate (if three phosphates bond), such as adenosine triphosphate (ATP). ATP is a crucial component of respiration and photosynthesis, amongst other processes.


Image Source: Wikimedia Commons

Figure iv: The molecular structure of nucleoside mono-, di- and triphosphate

is a concatenation of more 20 nucleotides joined by a phosphodiester bail.

The Pentose Carbohydrate

The pentose carbohydrate is a 5-carbon monosaccharide with the formula (CH2O)5.
These course 2 groups: aldopentoses and ketopentoses. The pentose sugars found in nucleotides are aldopentoses. Deoxyribose and ribose are two of these sugars.

These sugars differ in DNA and RNA. The sugar in Dna is
deoxyribonucleic acid, which contains deoxyribose. The carbohydrate in RNA is
ribonucleic acid, which contains ribose. The structural difference between these sugars is that ribonucleic acrid contains a hydroxyl (-OH) grouping, whereas deoxyribonucleic acrid contains only a hydrogen atom in the place of this hydroxyl group. Nucleotides which contain dna are known as deoxyribonucleotides. Those containing ribonucleic acid are known as ribonucleotides. Thus, the sugar molecule determines whether a nucleotide forms part of a DNA molecule or a RNA molecule. Below is a list of the names given to the sugars found in RNA and Dna.







Adenosine Adenylic acid Deoxyadenosine Deoxyadenylic acrid


Cytidine Cytidylic acid Deoxycytidine Deoxycytidylic acrid


Guanosine Guanylic acid Deoxyguanosine Deoxyguanylic acid


Uridine Uridylic acid


Deoxythymidine Deoxythymidylic acid

Putting it All Together

To epitomize, we have covered what a nucleotide is, what the 3 parts of a nucleotide are, we have covered the specifics of nitrogenous bases, pentose sugars, and phosphates, and nosotros accept discussed how nucleotides differ in DNA and RNA.

The phosphate is continued to the pentose sugar; the pentose sugar is connected to the nitrogenous base pair (A, C, G or T), which in DNA is continued to its base of operations pair partner. Something like this:


Image Source: Wikimedia Commons

Figure five: Nucleotide bonding in the DNA molecule with hydrogen and phosphate bonds.

The chemical structure of the phosphate, pentose carbohydrate, and nitrogenous bases of adenine, thymine, cytosine and guanine are shown above (figure 5).

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During DNA synthesis, a hydrogen bond joins A (adenine) to T (thymine), and C (cytosine) to G (guanine) (effigy 5). In RNA, uracil would supersede thymine.

A DNA strand is formed when the nitrogenous bases are joined by hydrogen bonds, and the phosphates of one group are joined to the pentose sugars of the adjacent grouping with a phosphodiester bond (effigy 5).

The double helix shape is the result of the hydrogen bonds betwixt the nitrogen bases, which form the “rungs” of the ladder while the phosphate and pentose saccharide (forming phosphodiester bonds) form the upright parts of the ladder.

To conclude, nucleotides are of import as they form the building blocks of nucleic acids, such as Dna and RNA. Nucleotides are made up of 3 parts. The first is a distinct nitrogenous base, which is adenine, cytosine, guanine or thymine. In RNA, thymine is replaced past uracil. These nitrogenous bases are either purines or pyrimidines. Base pairs are formed when adenine forms a hydrogen bond with thymine, or cytosine forms a hydrogen bail with guanine. The 2nd function of a nucleotide is the phosphate, which differentiates the nucleotide molecule from a nucleoside molecule. This phosphate is of import in the germination of phosphodiester bonds, which link several nucleotides in a linear manner. The third role of a nucleotide is the pentose (5 carbon) sugar. The pentose sugars institute in nucleotides are aldopentoses: ribose in RNA and deoxyribose in DNA. These sugars determine whether the nucleotide will class part of a Dna or a RNA molecule, and form role of the phosphodiester bonds which link several nucleotides. The combination of hydrogen bonds between nitrogenous bases and phosphodiester bonds between phosphates and sugars is what gives DNA its double helix shape.

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Nucleotides - Cellular and Molecular Biology Practice Question

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Which of the Following Could Be a Nucleotide of Dna

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