Nucleotide - Meaning, Structure, Types, Functions and Nucleosides

Nucleotide Definition: A nucleotide is an organic molecule composed of a nitrogenous base, a pentose sugar, and a phosphate group. DNA and RNA are polynucleotides, chains of nucleotide monomers with different nitrogenous bases. Nucleotides are crucial for metabolic and physiological activities. ATP (Adenosine triphosphate) is the energy currency of cells. Nucleotides also form coenzymes and cofactors like NAD, NADP, FAD, and coenzyme A, which are essential for metabolic processes.

Free Study Material for NEET Preparation

Nucleotide Meaning

Nucleotide Structure

• Purines, such as adenine (A) and guanine (G), feature a double-ring structure.
• Pyrimidines, including cytosine (C) and thymine (T) in DNA (or uracil (U) in RNA), possess a single-ring structure.

NEET Exam

Nucleotide Types

1. Ribonucleotides: These nucleotides contain a sugar molecule known as ribose. They serve as the fundamental units of ribonucleic acid (RNA), which plays a crucial role in various cellular processes such as protein synthesis.
2. Deoxyribonucleotides: These nucleotides contain a sugar molecule called deoxyribose, which lacks one oxygen atom compared to ribose. They are the building blocks of deoxyribonucleic acid (DNA), the genetic material responsible for storing and transmitting an organism's genetic information.

• Purines: These nitrogenous bases are larger and have a double-ring structure. Adenine (A) and guanine (G) are purines found in both DNA and RNA.
• Pyrimidines: These nitrogenous bases are smaller and have a single-ring structure. Cytosine (C) is a pyrimidine found in both DNA and RNA, while thymine (T) is specific to DNA and uracil (U) is specific to RNA.

Okazaki Fragments

Nucleotide Functions

• Formation of DNA and RNA: Nucleotides combine to create the structural framework of DNA and RNA molecules, which are responsible for storing and transmitting genetic information.
• Cellular Energy Transmission: Adenosine triphosphate (ATP), a nucleotide, serves as a primary carrier of energy within cells. ATP stores energy in its phosphate bonds and releases it to power cellular activities.
• Cellular Signalling: Specific nucleotides, such as cyclic AMP (cAMP), play roles in cell signalling pathways. cAMP helps regulate cellular processes like growth and differentiation.
• Coenzyme Activity: Many nucleotides function as components of coenzymes, which are essential for enzyme activity. Coenzymes are involved in various metabolic reactions.
• Maintenance of Cell Structure: Nucleotides are integral to certain cell membranes, contributing to the maintenance of cell shape and integrity.
• Precursors for Molecule Synthesis: Nucleotides serve as precursors for the synthesis of important molecules in the body, including amino acids and sugars.

lymphocytes

Nucleotide Synthesis

1. De novo synthesis: This pathway involves building nucleotides from basic components such as amino acids, bicarbonate, and ATP. It is a complex and energy-intensive process, mainly occurring in the liver in animals.
2. Salvage pathway: This pathway recycles existing nucleotides by salvaging their components, such as nucleobases and nucleosides, from degraded nucleic acids. It is a more energy-efficient process and can occur in most cells.

1. Pentose sugar phosphorylation: A pentose sugar (ribose for RNA or deoxyribose for DNA) is phosphorylated by ATP to form a pentose phosphate.
2. PRPP synthesis: The pentose phosphate is linked to pyrophosphate to form PRPP.
3. Nitrogenous base attachment: An appropriate nitrogenous base (purine or pyrimidine) is attached to PRPP to form a nucleoside phosphate.
4. Phosphate group addition: One or two phosphate groups are added to the nucleoside phosphate to form nucleotide diphosphate (NDP) or triphosphate (NTP), which are the activated forms of nucleotides used in cellular processes.

Explore NEET Online Courses by PW

Nucleotide in DNA

1. Nitrogenous base: Nitrogenous bases are of two types, purines (adenine and guanine) and pyrimidines (cytosine and thymine).
2. Pentose sugar: In DNA, the sugar is specifically called deoxyribose.
3. Phosphate group: This group imparts a negative charge to nucleotides.

Nucleotide Application

1. Building blocks of nucleic acids: Nucleotides are the basic units that combine to form nucleic acids, specifically DNA and RNA. These molecules are essential for storing and transmitting genetic information, which is crucial for all biological processes.
2. Cellular energy transfer and signalling: Certain nucleotides, such as adenosine triphosphate (ATP), are crucial in transferring energy within cells. ATP is a primary energy source for cellular activities like muscle contraction, protein synthesis, and nerve impulse transmission. By transferring phosphate groups to other molecules, ATP fuels these processes. Other nucleotides like cyclic AMP (cAMP) also act as secondary messengers in cellular signalling pathways.

Nucleotide Examples

1. Adenine (A): Adenine is one of the four nucleobases in DNA and RNA. It forms base pairs with thymine in DNA and with uracil in RNA.
2. Thymine (T): Thymine is a nucleobase exclusively found in DNA. It forms base pairs with adenine in DNA.
3. Cytosine (C): Cytosine is a nucleobase found in DNA and RNA. It pairs with guanine in the base pairing of both DNA and RNA.
4. Guanine (G): Guanine is a nucleobase in both DNA and RNA. It pairs with cytosine in the base pairing of both DNA and RNA.
5. Uracil (U): Uracil is a nucleobase solely found in RNA. It pairs with adenine in RNA.

Nucleotide Vs Nucleoside