The structure and functions of DNA and RNA (table)

It is well known that all forms of living matter, from viruses to highly organized animals (including humans), have a unique hereditary apparatus. It is represented by molecules of two types of nucleic acids: deoxyribonucleic and ribonucleic. In these organic substances, information is encoded that is transmitted from the parent to the offspring during reproduction. In this paper, we will study both the structure and functions of DNA and RNA in a cell, and also consider the mechanisms that underlie the processes of transmission of the hereditary properties of living matter.

As it turned out, the properties of nucleic acids, although they have some common features, nevertheless differ in many respects. Therefore, we compare the functions of DNA and RNA carried out by these biopolymers in the cells of various groups of organisms. The table presented in the work will help to understand what their fundamental difference consists in.

Nucleic Acids - Complex Biopolymers

The discoveries in the field of molecular biology that took place at the beginning of the 20th century, in particular, the decoding of the structure of deoxyribonucleic acid, served as an impetus for the development of modern cytology, genetics, biotechnology, and genetic engineering. From the point of view of organic chemistry, DNA and RNA are high molecular weight substances consisting of multiple repeating units - monomers, also called nucleotides. It is known that they are interconnected, forming chains capable of spatial self-organization.

Such DNA macromolecules often bind to special proteins that have special properties called histones. Nucleoprotein complexes form special structures - nucleosomes, which, in turn, are part of the chromosomes. Nucleic acids can be found both in the nucleus and in the cytoplasm of a cell, being present in some of its organelles, for example, mitochondria or chloroplasts.

The spatial structure of the substance of heredity

To understand the functions of DNA and RNA, you need to understand in detail the features of their structure. Like proteins, nucleic acids have several levels of organization of macromolecules. The primary structure is represented by polynucleotide chains, the secondary and tertiary configurations are self-complicated due to the emerging covalent type of bond. A special role in maintaining the spatial shape of the molecules belongs to hydrogen bonds, as well as to the van der Waals forces of interaction. The result is a compact DNA structure called a supercoil.

Nucleic Acid Monomers

The structure and functions of DNA, RNA, proteins, and other organic polymers depend on both the qualitative and quantitative composition of their macromolecules. Both types of nucleic acids are composed of structural elements called nucleotides. As you know from the chemistry course, the structure of a substance necessarily affects its function. DNA and RNA are no exception. It turns out that the type of acid itself and its role in the cell depend on the nucleotide composition. Each monomer contains three parts: a nitrogenous base, a carbohydrate, and phosphoric acid residue. Four types of nitrogenous bases for DNA are known: adenine, guanine, thymine, and cytosine. In RNA molecules, they will be, respectively, adenine, guanine, cytosine and uracil. Carbohydrate is represented by various types of pentose. Ribose is in ribonucleic acid, and its oxygen-free form, called deoxyribose, is in DNA.

Features of deoxyribonucleic acid

First we look at the structure and functions of DNA. RNA with a simpler spatial configuration will be studied by us in the next section. So, two polynucleotide filaments are held together by repeatedly repeated hydrogen bonds formed between nitrogenous bases. Two are present in the adenine-thymine pair, and three hydrogen bonds in the guanine-cytosine pair.

The conservative correspondence of purine and pyrimidine bases was discovered by E. Chargaff and was called the principle of complementarity. In a single chain, nucleotides are interconnected by phosphodiester bonds formed between pentose and the residue of phosphoric acid from adjacent nucleotides. The spiral appearance of both chains is supported by hydrogen bonds arising between the hydrogen and oxygen atoms in the nucleotides. The highest - tertiary structure (superspiral) - is characteristic of nuclear DNA of eukaryotic cells. In this form, it is present in chromatin. However, bacteria and DNA viruses have deoxyribonucleic acid that is not bound to proteins. It is represented by an annular shape and is called a plasmid.

The DNA of mitochondria and chloroplasts, organelles of plant and animal cells, has the same form. Next, we will find out how the functions of DNA and RNA differ from each other. The table below will show us these differences in the structure and properties of nucleic acids.

Ribonucleic acid

An RNA molecule consists of a single polynucleotide strand (the exception is the double-stranded structure of some viruses), which can be located both in the nucleus and in the cell cytoplasm. There are several types of ribonucleic acids that differ in structure and properties. So, messenger RNA has the highest molecular weight. It is synthesized in the nucleus of a cell on one of the genes. The task of mRNA is to transfer information about the composition of the protein from the nucleus to the cytoplasm. The transport form of the nucleic acid attaches to the protein monomers - amino acids - and delivers them to the site of biosynthesis.

Finally, ribosomal RNA is formed in the nucleolus and is involved in protein synthesis. As you can see, the functions of DNA and RNA in cellular metabolism are diverse and very important. They will depend, first of all, on the cells of which organisms contain the molecules of the substance of heredity. So, in viruses, ribonucleic acid can act as a carrier of hereditary information, whereas in cells of eukaryotic organisms only deoxyribonucleic acid has this ability.

Functions of DNA and RNA in the body

In their importance, nucleic acids, along with proteins, are the most important organic compounds. They preserve and transmit hereditary properties and traits from the parent to the offspring. Let's determine the difference between the functions of DNA and RNA. The table below will show these differences in more detail.

What are the characteristics of the substance of the heredity of viruses?

Virus nucleic acids can take the form of either single or double strand helices or rings. According to the classification of D. Baltimore, these objects of the microworld contain DNA molecules consisting of one or two chains. The first group includes the causative agents of herpes and adenoviruses, and the second group includes, for example, parvoviruses.

The functions of DNA and RNA viruses consist in the penetration of their own hereditary information into the cell, the replication of viral nucleic acid molecules and the assembly of protein particles in the ribosomes of the host cell. As a result, the entire cellular metabolism is completely subordinated to parasites, which, rapidly multiplying, lead the cell to death.

RNA viruses

In virology, the division of these organisms into several groups is customary. So, the first refers to species that are called single-stranded (+) RNA. Their nucleic acid performs the same functions as the messenger RNA of eukaryotic cells. The other group includes single-stranded (-) RNA. First, transcription occurs with their molecules, leading to the appearance of (+) RNA molecules, and those, in turn, serve as a matrix for the assembly of viral proteins.

Based on the foregoing, for all organisms, including viruses, the functions of DNA and RNA are briefly characterized as follows: the storage of hereditary traits and properties of the organism and their further transmission to offspring.