The nucleic acid is an important molecule in living organisms. Nucleic acid functions as the blueprint for genetic information. Understanding the nucleic acid structure and functions helps in deciphering the genetic code, which contains instructions for building and maintaining living organisms.

In this article, we will cover nucleic acid definition, structure, functions, formula and more.

Nucleic Acid Meaning

Nucleic acids are essential molecules found in all living organisms, including DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). They play crucial roles in storing and transmitting genetic information, controlling cellular processes, and enabling protein synthesis. DNA carries the genetic instructions for the development, functioning, growth, and reproduction of organisms, while RNA helps in decoding these instructions and translating them into proteins.

Nucleic Acid Discovered By

Nucleic acids were discovered by Friedrich Miescher in 1869. While working with white blood cells from pus-soaked bandages, Miescher isolated a substance he called “nuclein” from the cell nuclei. This substance, later identified as DNA, laid the foundation for understanding the molecular basis of genetics. Miescher’s work was crucial in the study of heredity and molecular biology.

Nucleic Acid Structure

Nucleic acids are made up of nucleotides, which consist of a sugar molecule, a phosphate group, and a nitrogenous base. In DNA, the nitrogenous bases include adenine (A), cytosine (C), guanine (G), and thymine (T), while RNA substitutes uracil (U) for thymine. These nucleotides link together to form long chains, with the sugar-phosphate backbone providing stability and the sequence of nitrogenous bases encoding genetic information.

Sugar

Typically, this sugar has five carbons. i.e a pentose. These sugars, together with the phosphate groups found in nucleotides, combine to create a bond. The carbohydrate that is found in the biomolecule of DNA is deoxyribose, while the carbohydrate in the biomolecule of RNA is ribose.

Also Read: What are the Three Main Parts of a Nucleotide?

The Group of Phosphates

In other words, they are the phosphates that are derived from the inorganic substance known as phosphoric acid. H3PO4. They establish an ester bond by combining forces with the sugars present in the nucleotides. Phosphate groups might show up in nucleic acids in a variety of different combinations.

Nitrogenous Base

Nitrogenous bases are organic molecules that form the building blocks of nucleic acids. These bases: adenine, cytosine, guanine, thymine (in DNA), and uracil (in RNA), pair up to form the genetic code.

Nucleic Acids Structure

Nitrogenous Base of Nucleic Acids – Purine and Pyrimidine

There are two types of nitrogenous bases present:

• Purines: Purines are larger, double-ring structures consisting of adenine (A) and guanine (G). Adenine pairs with thymine (in DNA) or uracil (in RNA) via hydrogen bonds, while guanine pairs with cytosine via similar bonds.
• Pyrimidines: Pyrimidines are smaller, single-ring structures consisting of cytosine (C), thymine (in DNA), uracil (in RNA), and the less common base, cytosine (C). Pyrimidines pair with complementary bases: cytosine pairs with guanine, and thymine (in DNA) or uracil (in RNA) pairs with adenine.

Now let’s discuss it in detail.

Purine

The two main purines found in nucleic acids are adenine (A) and guanine (G).

Adenine

Adenine (A) is a purine nucleobase which plays a critical role in storing and transmitting genetic information. Within DNA, adenine pairs with thymine (T) via hydrogen bonds, forming the double helix structure. In RNA, uracil (U) replaces thymine and also binds with adenine.

To form nucleotides, adenine combines with a pentose sugar (ribose in RNA, deoxyribose in DNA) and a phosphate group. The resulting molecule is named based on the base and sugar type: “adenosine” for adenine and ribose, “deoxyadenosine” for adenine and deoxyribose. Nucleotides can have one, two, or three phosphate groups attached, denoted by suffixes like “monophosphate,” “diphosphate,” and “triphosphate” (e.g., adenosine triphosphate, ATP). Both DNA and RNA are polymers constructed from these nucleotides.

Hydrogen bonding between complementary bases (adenine with thymine in DNA, adenine with uracil in RNA) is crucial for maintaining the structure of nucleic acids and facilitating processes like DNA replication and protein synthesis. These hydrogen bonds can also participate in enzymatic reactions, influencing their rates.

Guanine

Guanine, denoted by the letter G, is a purine nucleobase with the chemical formula C5H5N5O. Found in both DNA and RNA, guanine forms hydrogen bonds with cytosine, a complementary pyrimidine nucleobase. Guanine, along with adenine and cytosine, is present in both DNA and RNA. However, thymine is typically found only in DNA, while uracil takes its place in RNA. Dietary sources of guanine are primarily animal-based, with high concentrations found in organ meats like liver, brain, and kidneys. Plant sources like peas, beans, and lentils contain smaller amounts.

Guanine exists in two tautomeric forms: the predominant keto form and the rare enol form. When paired with cytosine in DNA or RNA, three hydrogen bonds form between the two molecules. In cytosine, the amino group acts as the hydrogen bond donor, while the C-2 carbonyl group and the N-3 amine group in guanine act as hydrogen bond acceptors. The C-6 carbonyl group in guanine serves as an additional hydrogen bond acceptor, while the N-1 position and the amino group at C-2 in guanine act as hydrogen bond donors.

Pyrimidines

Pyrimidines are single-ring nitrogenous bases, including cytosine, thymine (in DNA), and uracil (in RNA), essential for encoding genetic information.

Thymine

5-methyl uracil is another name for thymine. Thymine is a pyrimidine that binds to adenine in DNA. Thymine is written with a capital letter T. The formula for this is C5H6N2O2. 

It  is a pyrimidine nitrogen base. It is made from uracil with a methyl group in place of the hydrogen at the fifth position. In humans, E.coli, and rodents, it serves as a metabolite and plays a function in the metabolic process. It is a nucleobase made of pyrimidine and a pyrimidone.

Cytosine

The capital letter C stands for cytosine. It covalently bonds to the guanine found in DNA and RNA. In the Watson-Crick base pairing process, cytosine and guanine make three hydrogen bonds with each other. This is how DNA is made. Cytosine is made up of the atoms C4H4N2O2. Cytidine is the nucleotide that is made out of cytosine.

Cytosine is a type of pyrimidine base that pairs with guanine. It may be present in the RNA as well as the DNA. Cytosine is an aminopyrimidine, which is pyrimidine-2-one with an amino group at position-4. It functions as a metabolites in human cells, as well as in E.coli cells, Saccharomyces cerevisiae cells, and mouse cells. 

Uracil

Uracil is like thymine that has been stripped of its methyl group. Uracil is shown by the letter U with a capital letter. The formula for this is C4H4N2O2. In nucleic acids, it is linked to adenine in RNA. The nucleotide uridine is made up of uracil. In nature, there are many other nitrogenous bases, and the molecules can also be found in other compounds. For example, pyrimidine rings can be found in nucleotides, thiamine (vitamin B1), and barbituates.

Some meteorites also have pyrimidines, but no one knows where they came from. Nature also has xanthine, theobromine, and caffeine, which are all purines. By forming bonds with ribose and phosphates, it helps make many enzymes that are needed for a cell to work. Uracil is a coenzyme and an allosteric regulator that is used in both animal and plant reactions.

Nucleic Acid Function

The function of nucleic acid is given below:

• Nucleic acids, including DNA and RNA, serve as the carriers of genetic information in all living organisms.
• They encode the instructions necessary for the development, growth, and functioning of cells.
• Nucleic acids play a central role in protein synthesis, where the information encoded in DNA is transcribed into RNA and then translated into proteins.
• They are involved in the regulation of gene expression, controlling which genes are turned on or off in response to environmental cues or cellular needs.
• Nucleic acids also participate in various cellular processes such as DNA replication, repair, and recombination, essential for maintaining genetic integrity.
• Additionally, some nucleic acids, such as ribosomal RNA (rRNA) and transfer RNA (tRNA), are structural components of ribosomes and are directly involved in protein synthesis.

Nucleic Acid Examples

Some of the examples of nucleic acid are:

DNA (Deoxyribonucleic Acid)

DNA is a double-helix composed of two long strands of nucleotides. Each nucleotide consists of a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases: adenine (A), thymine (T), cytosine (C), or guanine (G). The strands are held together by hydrogen bonds between complementary bases (A pairs with T, and C pairs with G).

RNA (Ribonucleic Acid)

RNA is typically single-stranded and composed of nucleotides containing ribose sugar, a phosphate group, and one of four nitrogenous bases: adenine (A), uracil (U), cytosine (C), or guanine (G). Unlike DNA, RNA’s structure allows it to fold into various shapes, enabling its diverse functions in protein synthesis and regulation.

Conclusion – Nucleic Acid

In conclusion, nucleic acids, encompassing DNA and RNA, serve as fundamental molecules governing life processes in all organisms. They harbor genetic information crucial for cellular development, growth, and function. DNA carries this genetic blueprint, while RNA aids in its decoding and translation into proteins. The structure of nucleic acids, composed of nucleotides containing sugar molecules, phosphate groups, and nitrogenous bases, underpins their function in storing and transmitting genetic data.

Also Read:

• What are the Three Main Parts of a Nucleotide?
• Difference Between DNA and RNA
• RNA Full Form
• Biomolecules – Definition, Structure, Classification, Examples
• Difference Between Purines and Pyrimidines
• Stability of Protein
• Nitrogenous Bases

FAQs on Nucleic Acid

What is called Nucleic Acid?

Nucleic acids are molecules that store and transmit genetic information in living organisms.

What are the 3 Nucleic Acids?

The three main nucleic acids are DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and ATP (adenosine triphosphate).

What is the Main Function of the Nucleic Acid?

The main function of nucleic acids is to carry genetic information, control cellular processes, and facilitate protein synthesis.

Where are Nucleic Acids?

Nucleic acids are found in the nuclei of cells and in organelles like mitochondria and chloroplasts. They’re also present in viruses.

What are Nucleic Acid Examples?

Examples of nucleic acids include DNA, RNA, and ATP. Other examples are nucleotide derivatives like cAMP (cyclic adenosine monophosphate) and coenzymes like NADH (nicotinamide adenine dinucleotide).

What is Nucleic Acid Formula?

Nucleic acids, DNA and RNA, don’t have a single chemical formula since they are polymers made up of varying sequences of nucleotides. Each nucleotide includes a sugar (deoxyribose in DNA, ribose in RNA), a phosphate group, and a nitrogenous base.