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Nucleotides - Structure, Difference Between Nucleotides and Nucleosides, Functions, Biological Importance, Practice Questions, Frequently Asked Questions - FAQs

Nucleotides - Structure, Difference Between Nucleotides and Nucleosides, Functions, Biological Importance, Practice Questions, Frequently Asked Questions - FAQs

A bird, human, ferret, or another animal must constantly make new cells to replace dying ones in order to live, grow, and develop. To keep the body as it is, millions of cells must be produced every minute. While these animals all seem unique, we must understand that they have more in common than what meets the eye.

Of course by now you know that carbon is the basis of all organic matter. However, there are other members of the periodic table without whom life as we know it would not be possible. Of course, I am talking about chemical atoms like hydrogen, oxygen, and nitrogen. Nitrogen is in fact responsible for proteins aka the building blocks of all living things. One very important nitrogen based molecule is called a "nucleotide". All cells must all generate new cells with nucleotides, relying on DNA and RNA to do so correctly. The human body requires sufficient nucleotides for appropriate functioning and health, and it always finds a method to obtain them. This is significant since nucleotides are engaged in practically all of the cell's actions, either alone or in combination with other molecules (and therefore, the body).

Now before we get confused with lots of questions about Nucleotides, let’s first understand what Nucleotide is? Why is it so important? What are its functions? Where do these nucleotides come from?

Let’s begin!

Table of content:

  • Nucleotide
  • Structure of Nucleotide
  • Difference between nucleotides and nucleosides
  • Functions of nucleotides
  • Biological importance of nucleotide
  • Practice questions
  • Frequently asked questions - FAQs


A nitrogenous base, pentose sugar, and phosphate make up the core parts of a nucleotide, an organic molecule. These molecules can seem insignificant, but the human body depends heavily on them.

A chain of nucleotide monomers with different nitrogenous bases makes up polynucleotides like DNA and RNA.

For metabolic and physiological processes to take place, nucleotides are necessary.

ATP is the currency of energy in cells (adenosine triphosphate). Because they produce a variety of coenzymes and cofactors, including flavin adenine dinucleotide (FAD), coenzyme A, nicotinamide adenine dinucleotide phosphate (NADP), and others, nucleotides are essential for many metabolic processes.

Structure of nucleotide:

A nucleotide is made up of three covalently bonded units. They're as follows:

1. Bases containing nitrogen - Pyrimidine and Purine
2. Ribose and Deoxyribose are both found in pentose sugar.
3. Monophosphate, diphosphate, and triphosphate are all types of phosphate.

1. Nitrogenous base: They contain purine or pyrimidine as a nitrogenous base. Adenine (A), guanine (G), thymine (T), and cytosine (C) are found in DNA, while adenine(A), guanine(G), uracil (U), and cytosine(C) are found in RNA.

Below are the structures and descriptions of the five nitrogenous bases.

  • Adenine is a purine derivative composed of two nitrogen-containing rings. In the nucleotide structure, it creates a double bond with thymine.
  • Guanine is another purine derivative with two nitrogen-containing rings. In the nucleotide structure, it forms a triple bond with cytosine.
  • Thymine is a pyrimidine derivative with a single nitrogen-containing ring. 5-methyluracil is another name for it.
  • Cytosine is a pyrimidine derivative that is formed up of an aromatic ring connected to an amino and keto group, similar to thymine.
  • Uracil is a pyrimidine derivative that might be considered a demethylated version of thymine.
  1. Sugar: A pentose sugar is found in a nucleotide. Deoxyribose sugar is found in DNA (Deoxyribonucleic acid), while ribose sugar is found in RNA (Ribonucleic acid).

Note: A nucleoside is a nitrogenous base that is linked to sugar.

  1. Phosphate: Phosphate forms an ester link with the 5th C hydroxyl group on the sugar of the nucleoside. At least one phosphate group is present in nucleotides.

A 5'-3' linkage is formed when the phosphate of one nucleotide connects to the 3rd C-OH group of the sugar of the second nucleotide.

Two antiparallel strands of polynucleotides are joined together by hydrogen bonds between nitrogenous bases in DNA (double helix). Purine forms two hydrogen bonds with the pyrimidine base, while A bonds with T and G bonds with C.

Note: Instead of thymine (T), Adenine (A) interacts with Uracil (U) in RNA.

The phosphate group forms a chain by linking the sugar molecules of two nucleotides. Polynucleotides include DNA and RNA. A polynucleotide chain's backbone is made up of sugar-phosphate chains.

Difference between nucleotides and nucleosides:

Nucleoside = Sugar + Nitrogenous base

Adenosine, Guanosine, Thymidine, Cytidine, and Uridine are examples of nucleosides.

Nucleotide = Phosphate + Nucleoside

Adenylic acid, Guanylic acid, Thymidylic acid, Cytidylic acid, and Uridylic acid are examples of nucleotides.

Functions of nucleotides:

  • The building blocks of DNA and RNA are nucleotides. They have genetic information in them.
  • Nucleotides are coenzymes that enzymes use to catalyze a variety of biological activities.
  • Higher nucleotides, such as ATP, GTP, UTP, and TTP, serve as energy carriers. Among these, ATP is the cell's universal energy transporter.

  • Nucleotides are required for cell repair and replacement.
  • Nucleotides are necessary for the immune system's normal functioning, cell repair after injury or sickness, and disease prevention.

Biological importance of nucleotide:

Nucleotides have various biological advantages and significance, making them incredibly important and a major component of RNA and DNA. The biological significance of nucleotides is listed below. These are

  1. Nucleotides are the building blocks of Ribonucleic Acid (RNA) and Deoxyribonucleic Acid (DNA).
  2. It has proven to be effective as an antiviral in the treatment of diseases such as hepatitis and HIV.
  3. Aids in the development of cell metabolism in living beings.
  4. Food groups such as protein, carbs, and fats all benefit from it.
  5. It's one of the body's most energy-producing organic compounds.
  6. Increasing the amount of nucleotides in one's diet enhances muscular joints and reduces discomfort.
  7. It is responsible for every human being's hereditary character.

Practice questions:

Q1: The following elements make up a nucleotide:

A. A phosphorous base, nitrogenous group, a tetrose sugar
B. A phosphate group, nitrogenous base, a hexose sugar
C. A nitrogenous base, phosphate group, a hexose sugar
D. A nitrogenous base, phosphate group, a pentose sugar
Answer: D

Solution: A nucleotide is the most fundamental component of nucleic acids (RNA and DNA). A sugar molecule (ribose in RNA or deoxyribose in DNA) is bonded to a phosphate group and a nitrogen-containing base to form a nucleotide.

So, option D is the correct answer.

Q2: In the context of genetic material: Base + Sugar →

A. Nucleoside
B. Nucleotide
C. Nuclein
D. Nucleic acid
Answer: A

Solution: Base + Sugar → Nucleoside

So, option A is the correct answer.

Q3: DNA is a polymer of

A. Ribonucleotides
B. Nucleotides
C. Deoxyribonucleotides
D. Nucleosides
Answer: C

Solution: Nucleotides are the building blocks of Ribonucleic Acid (RNA) and Deoxyribonucleic Acid (DNA). and DNA is a polymer of deoxyribonucleotides.

So, option C is the correct answer.

Q4: 3′ end of the polynucleotide chain bears

A. Hydroxyl group
B. Phosphate group
C. Nitro group
D. Methyl group
Answer: A

Solution: By looking at the structure we can say that option A is the correct answer.

Frequently asked questions - FAQs

Q1: What role do nucleotides play in a cell?
Nucleotides are the building blocks of Ribonucleic Acid (RNA) and Deoxyribonucleic Acid (DNA). It has proven to be effective as an antiviral in the treatment of diseases such as hepatitis and HIV. Aids in the development of cell metabolism in living beings.

Q2: What type of sugar is found in nucleic acids?
The sugar contained in nucleotides and nucleic acids is pentose. Ribose is the sugar in RNA and its nucleotide, whereas Deoxyribose is the sugar in DNA and its nucleotide.

Q3:What are four types of nucleotides?
Polynucleotides include DNA and RNA. The nitrogenous bases, pentose sugar, and phosphate that make up nucleotides are joined together. There are four different nitrogenous bases in each of the four types of nucleotides. The nitrogenous bases adenine, guanine, thymine, and cytosine are found in DNA while uracil is used in place of thymine in RNA. Nucleotides include adenylic acid, guanylic acid, thymidylic acid, uridylic acid, and cytidylic acid.

Q4: What happens when nucleotides come together to make nucleic acids?
The nucleotides unite to produce a nucleic acid, such as DNA or RNA. A nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group are the three components of each nucleotide. A sugar molecule is linked to one or more phosphate groups for each nitrogenous base in a nucleotide.

Related links:

Functions of nucleic acids


Carbohydrates- Sugars-classification of carbohydrates and its structure


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