Which is Not a Component of a Nucleotide

Which is Not a Component of a Nucleotide.

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?


Image Source: Wikimedia Commons

Figure one: 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 construction ofDNA’south can exist visualized or thought of similar a ladder. If we continue with this illustration, each “step or rung” of this ladder is made up of a cord of
nucleotides, in a very specific and controlled club. Each nucleotide, in turn, is made upward of a
nitrogenous base, a
pentose sugar,
and a
phosphate. InFigure two, the nitrogenous base of operations is enclosed in the red square on the right, while the phosphate is enclosed in the blue square on the left. The residual of the molecule forms the pentose saccharide. This particular molecule is adenine; we will find out more most this later.


Image Source: Wikimedia Commons

Effigy 2: The chemical associates of the three parts of the nucleotide, the phosphate (blue box), nitrogenous base (ruby box) and the pentose sugar. This item nucleotide is adenine

The assembly of nucleotides (1) differentiates them from nucleosides, which do not incorporate a phosphate grouping (in the blue box); (2) allows the nucleotide to connect to other nucleotides when the nitrogenous base forms a hydrogen bail with another nucleotide’southward nitrogenous base; every bit well equally (3) allows the phosphate to form a phosphodiester bail with some other nucleotide’s pentose carbohydrate. This results in a complex double-stranded “cord or ladder”, as seen in figure1.This is the footing of the grade of Dna.

The Nitrogenous Base of operations

The word “nucleotide” was first coined by P.A. Levene, who observed that Deoxyribonucleic acid contained four similar building blocks, in roughly equal amounts. These building blocks are what we now know as the
nitrogenous bases
institute in DNA and RNA.

A nitrogenous base of operations is a molecule containing nitrogen, with the chemical properties of a base due to a pair of electrons on the nitrogen cantlet. These nitrogenous bases are Adenine (A), Cytosine (C) and Guanine (G) which are establish in both RNA and DNA so Thymine (T) which is only institute in Deoxyribonucleic acid and Uracil (U), which takes the place of Thymine in RNA.

Nitrogenous bases can be further classified as
purines. Cytosine, uracil and thymine are all pyrimidines. That is, their molecular structure comprises a nitrogenous base of operations in the form of a
six-member single ring. Guanine and adenine, on the other hand, are purines. These contain a nitrogenous base of operations in the form of a
nine-fellow member double ring. In short, pyrimidines have only one ring while purines have ii (figure 3).

Now that y’all get the general thought of purines versus pyrimidines permit’s speak biochemistry. A purine is a heterocyclic aromatic organic compound that comprises of a pyrimidine ring that is joined to an imidazole ring. The adjacent logical question, of course, becomes“what and so is a pyrimidine, biochemically speaking”? Well, pyrimidines are a class of nitrogenous compounds that take only i heterocyclic ring.


Image Source: Wikimedia Commons

Figure iii: Chemic construction of purines (A, G) and pyrimidines (C, T/U)

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

This pairing is, therefore, crucial for genetic role, and is the foundation for Deoxyribonucleic acid replication and gene expression. The order in which base pairs appear determines the functioning of your physiology. In protein synthesis, for example, the code is read in triplicates where three bases code for a particular amino acid. Deletions and insertions of nucleotides in this situation can lead to a complete frame shift disrupting the synthesis of the protein in question. Substitutions tin also exist problematic although less so, as they may alter the identity of an amino acid in the protein code.

The Phosphate Group

The phosphate grouping (PO4) is what differentiates a nucleotide from a nucleoside. This improver changes the nucleoside from a base of operations 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, as the hydrogen bonds which join the nitrogenous bases are non very strong. These sides of the ladder are hydrophilic (attracted to water), allowing the DNA molecule to bail with h2o.

What are Nucleoside Diphosphates and Triphosphates?

Y’all know that a nucleotide is differentiated from a nucleoside by one phosphate group. Appropriately, a nucleotide tin also exist a
nucleoside monophosphate(effigy 4). If more phosphates bond to the nucleotide (nucleoside monophosphate) it can become a nucleoside diphosphate (if two phosphates bail), or a nucleoside triphosphate (if iii phosphates bond), such equally adenosine triphosphate (ATP). ATP is a crucial component of respiration and photosynthesis, amongst other processes.


Epitome Source: Wikimedia Commons

Figure 4: The molecular structure of nucleoside mono-, di- and triphosphate

is a chain of more than 20 nucleotides joined by a phosphodiester bail.

The Pentose Sugar

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

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







Adenosine Adenylic acid Deoxyadenosine Deoxyadenylic acid


Cytidine Cytidylic acrid Deoxycytidine Deoxycytidylic acid


Guanosine Guanylic acid Deoxyguanosine Deoxyguanylic acid


Uridine Uridylic acid


Deoxythymidine Deoxythymidylic acid

Putting it All Together

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

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


Image Source: Wikimedia Commons

Figure 5: Nucleotide bonding in the Deoxyribonucleic acid molecule with hydrogen and phosphate bonds.

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

During Dna synthesis, a hydrogen bail joins A (adenine) to T (thymine), and C (cytosine) to M (guanine) (figure 5). In RNA, uracil would supervene upon 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 next grouping with a phosphodiester bond (effigy 5).

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

To conclude, nucleotides are of import as they grade the edifice blocks of nucleic acids, such equally Dna and RNA. Nucleotides are made upwardly of 3 parts. The beginning is a singled-out nitrogenous base, which is adenine, cytosine, guanine or thymine. In RNA, thymine is replaced by uracil. These nitrogenous bases are either purines or pyrimidines. Base of operations pairs are formed when adenine forms a hydrogen bond with thymine, or cytosine forms a hydrogen bail with guanine. The 2d part of a nucleotide is the phosphate, which differentiates the nucleotide molecule from a nucleoside molecule. This phosphate is important in the formation of phosphodiester bonds, which link several nucleotides in a linear way. The third function of a nucleotide is the pentose (5 carbon) sugar. The pentose sugars found in nucleotides are aldopentoses: ribose in RNA and deoxyribose in DNA. These sugars determine whether the nucleotide volition class office of a Dna or a RNA molecule, and form part 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 Deoxyribonucleic acid its double helix shape.

Let’s put everything into exercise. Try this Cellular and Molecular Biology practise question:

Nucleotides - Cellular and Molecular Biology Practice Question

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Which is Not a Component of a Nucleotide

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