what is the role of nucleic acid metabolism

Full Answer

What is the role of nucleic acid metabolism in DNA replication?

Nucleic acid metabolism generates and hydrolyzes DNA and RNA molecules and their components in the cell, in the processes of DNA replication, repair, recombination and turnover of DNA, transcription of RNA on DNA, and purine and pyrimidine synthesis and breakdown [1]. E. Dudley, ...

Is nucleic acid metabolism catabolic or anabolic?

Nucleic acid metabolism is the process by which nucleic acids ( DNA and RNA) are synthesized and degraded. Nucleic acids are the polymers of nucleotides. Nucleotide synthesis is an anabolic mechanism generally involving the chemical reaction of phosphate, pentose sugar, and a nitrogenous base. Destruction of nucleic acid is a catabolic reaction.

What are the functions of nucleic acids?

Nucleic acids are naturally occurring chemical compounds that serve as the primary information-carrying molecules in cells. They play an especially important role in directing protein synthesis. The two main classes of nucleic acids are deoxyribonucleic acid ( DNA) and ribonucleic acid ( RNA ).

What is DNA metabolism and why is it important?

DNA metabolism. Replication, repair, and recombination—the three main processes of DNA metabolism—are carried out by specialized machinery within the cell. DNA must be replicated accurately in order to ensure the integrity of the genetic code. Errors that creep in during replication or because of damage after replication must be repaired.

What is the process of synthesis and degradation of nucleic acids?

Nucleic acid metabolism is the process by which nucleic acids ( DNA and RNA) are synthesized and degraded. Nucleic acids are the polymers of nucleotides. Nucleotide synthesis is an anabolic mechanism generally involving the chemical reaction of phosphate, pentose sugar, and a nitrogenous base. Destruction of nucleic acid is a catabolic reaction. Additionally, parts of the nucleotides or nucleobases can be salvaged to recreate new nucleotides. Both synthesis and degradation reactions require enzymes to facilitate the event. Defects or deficiencies in these enzymes can lead to a variety of diseases.

Where are nucleotides produced?

Nucleotides can be separated into purines and pyrimidines. In the more complex multicellular animals they are both primarily produced in the liver. They both contain a sugar and a phosphate, but have nitrogenous bases that are different sizes. Because of this, the two different groups are synthesized in different ways.

How is uric acid excreted?

For example, adenine + PRPP --> AMP + PPi.

How do purines degrade to uric acid?

Purine degradation takes place mainly in the liver of humans and requires an assortment of enzymes to degrade purines to uric acid. First, the nucleotide will lose its phosphate through 5'-nucleotidase. The nucleoside, adenosine, is then deaminated and hydrolyzed to form hypoxanthine via adenosine deaminase and nucleosidase respectively. Hypoxanthine is then oxidized to form xanthine and then uric acid through the action of xanthine oxidase. The other purine nucleoside, guanosine, is cleaved to form guanine. Guanine is then deaminated via guanine deaminase to form xanthine which is then converted to uric acid. Oxygen is the final electron acceptor in the degradation of both purines. Uric acid is then excreted from the body in different forms depending on the animal.

What is the name of the nucleoside that is oxidized to form xanthine?

The nucleoside, adenosine, is then deaminated and hydrolyzed to form hypoxanthine via adenosine deaminase and nucleosidase respectively. Hypoxanthine is then oxidized to form xanthine and then uric acid through the action of xanthine oxidase. The other purine nucleoside, guanosine, is cleaved to form guanine.

What is the final electron acceptor in the degradation of both purines?

Guanine is then deaminated via guanine deaminase to form xanthine which is then converted to uric acid. Oxygen is the final electron acceptor in the degradation of both purines.

What happens to the carbon skeletons of pyrimidine?

Pyrimidine degradation ultimately ends in the formation of ammonium, water, and carbon dioxide. The ammonium can then enter the urea cycle which occurs in the cytosol and the mitochondria of cells.

What are the three main processes of DNA metabolism?

Replication, repair, and recombination —the three main processes of DNA metabolism—are carried out by specialized machinery within the cell. DNA must be replicated accurately in order to ensure the integrity of the genetic code.

Which enzyme adds single nucleotides to the 3′ end of an RNA or a DNA?

DNA polymerase adds single nucleotides to the 3′ end of either an RNA or a DNA molecule. In the prokaryote E. coli, there are three DNA polymerases; one is responsible for chromosome replication, and the other two are involved in the resynthesis of DNA during damage repair.

How is DNA replicated?

The leading strand is replicated continuously by adding individual nucleotides to the 3′ end of the chain. The lagging strand is synthesized in a discontinuous manner by laying down short RNA primers and then filling the gaps by DNA polymerase, such that the bases are always added in the 5′ to 3′ direction. The short RNA fragments made during the copying of the lagging strand are degraded when no longer needed. The two newly synthesized DNA segments are joined by an enzyme called DNA ligase. In this way, replication can proceed in both directions, with two leading strands and two lagging strands proceeding outward from the origin.

How does DNA replication work?

DNA replication is a semiconservative process in which the two strands are separated and new complementary strands are generated independently, resulting in two exact copies of the original DNA molecule. Each copy thus contains one strand that is derived from the parent and one newly synthesized strand. Replication begins at a specific point on a chromosome called an origin, proceeds in both directions along the strand, and ends at a precise point. In the case of circular chromosomes, the end is reached automatically when the two extending chains meet, at which point specific proteins join the strands. DNA polymerases cannot initiate replication at the end of a DNA strand; they can only extend preexisting oligonucleotide fragments called primers. Therefore, in linear chromosomes, special mechanisms initiate and terminate DNA synthesis to avoid loss of information. The initiation of DNA synthesis is usually preceded by synthesis of a short RNA primer by a specialized RNA polymerase called primase. Following DNA replication, the initiating primer RNAs are degraded.

Why do linear chromosomes have special mechanisms?

Therefore, in linear chromosomes, special mechanisms initiate and terminate DNA synthesis to avoid loss of information. The initiation of DNA synthesis is usually preceded by synthesis of a short RNA primer by a specialized RNA polymerase called primase. Following DNA replication, the initiating primer RNAs are degraded.

Why is recombination important?

Finally, recombination between genomes is an important mechanism to provide variation within a species and to assist the repair of damaged DNA.

What are the proteins that help to separate the two strands of DNA?

A number of other proteins are also essential for replication. Proteins called DNA helicases help to separate the two strands of DNA, and single-stranded DNA binding proteins stabilize them during opening prior to being copied. The opening of the DNA helix introduces considerable strain in the form of supercoiling, a movement that is subsequently relaxed by enzymes called topoisomerases ( see above Supercoiling ). A special RNA polymerase called primase synthesizes the primers needed at the origin to begin transcription, and DNA ligase seals the nicks formed between individual fragments.

Abstract

Nucleic acids are polymers of nucleotides. The latter are composed of a five-carbon sugar ( d -ribose or d -deoxyribose) linked both to a nitrogen base (purine or pyrimidine) and a phosphate group (nucleosides are nucleotides without this phosphate group).

Further Reading

Adams, R. L. P., Burdon, R. H., Campbell, A. M. and Smelle, R. M. S. (1976). David-son’s The Biochemistry of Nucleic Acids. Eighth edition, Chapman and Hall and Science Paperbacks, London Google Scholar

What is the role of nucleic acids in the cell?

Nucleic acids are the main information-carrying molecules of the cell and play a central role in determining the inherited characteristics of every living thing.

What are the building blocks of nucleic acids?

Nucleic acids are long chainlike molecules composed of a series of nearly identical building blocks called nucleotides. Each nucleotide consists of a nitrogen-containing aromatic base attached to a pentose (five-carbon) sugar, which is in turn attached to a phosphate group.

What are the two classes of nucleic acids?

They play an especially important role in directing protein synthesis. The two main classes of nucleic acids are deoxyribonucleic acid ( DNA) and ribonucleic acid ( RNA ).

How are nucleotides synthesized?

The ribose phosphate portion of both purine and pyrimidine nucleotides is synthesized from glucose via the pentose phosphate pathway. The six-atom pyrimidine ring is synthesized first and subsequently attached to the ribose phosphate. The two rings in purines are synthesized while attached to the ribose phosphate during the assembly of adenine or guanine nucleosides. In both cases the end product is a nucleotide carrying a phosphate attached to the 5′ carbon on the sugar. Finally, a specialized enzyme called a kinase adds two phosphate groups using adenosine triphosphate (ATP) as the phosphate donor to form ribonucleoside triphosphate, the immediate precursor of RNA. For DNA, the 2′-hydroxyl group is removed from the ribonucleoside diphosphate to give deoxyribonucleoside diphosphate. An additional phosphate group from ATP is then added by another kinase to form a deoxyribonucleoside triphosphate, the immediate precursor of DNA.

What is the chemical compound that is capable of being broken down to yield phosphoric acid, sugars, and?

Nucleic acid, naturally occurring chemical compound that is capable of being broken down to yield phosphoric acid, sugars, and a mixture of organic bases (purines and pyrimidines). Nucleic acids are the main information-carrying molecules of the cell, and, by directing the process of protein synthesis, they determine the inherited characteristics ...

What are the bases of nucleotides?

Each nucleic acid contains four of five possible nitrogen-containing base s: adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U). A and G are categorized as purines, and C, T, and ...

Which enzyme adds adenosine triphosphate to RNA?

Finally, a specialized enzyme called a kinase adds two phosphate groups using adenosine triphosphate (ATP) as the phosphate donor to form ribonucleoside triphosphate, the immediate precursor of RNA. For DNA, the 2′-hydroxyl group is removed from the ribonucleoside diphosphate to give deoxyribonucleoside diphosphate.

Why are nucleic acids consumed?

Nucleic acids are consumed in large quantities owing to their presence in all cells. These nucleic acids are not utilized by the body; instead they are digested, catabolized and excreted. They are taken in the form of nucleoproteins, which are conjugated proteins with amino acids constituting the protein part and nucleic acids constituting the prosthetic part.

What happens when nucleic acids are released?

Whenever there is cell death, the nucleic acids are released and converted to purines and finally uric acid is formed.

What is the end product of purine metabolism?

End product of purine metabolism is uric acid (in primates including man and dog). In lower animals, birds and reptiles, uric acid is converted to allantoin by the action of enzyme uricase. Liver, spleen, kidney, intestinal mucosa contain enzymes capable of acting on the purine ring in the free or combined state.

What happens when uric acid is too high?

If the concentration of uric acid exceeds 7 mg/100 ml in the blood plasma, the uric acid gets precipitated as sodium ureate crystals that cannot be excreted hence gets deposited in the soft tissues. There is abnormal deposition in joints and tendons. This abnormal deposition of sodium ureate crystals in soft tissue is known as TOPHI. Because of this the tissue gets degraded or degenerated at the bone joints leading to degeneration of neighbouring tissues as well. Degeneration causes inflammation of the joint.

What enzymes are responsible for absorbing nucleotides?

The protein part of nucleoprotein is acted upon by proteolytic enzymes of gastric and intestinal juices. Nucleic acids are acted upon by nucleases (ribonuclease and deoxyribonuclease) of pancreatic and intestinal juices to produce mononucleotides. Nucleotides are hydrolysed to nucleosides by nucleotidases (intestinal phosphatase) Nucleosides are absorbed by intestinal mucosa to portal blood and transported to the liver and supplied through systemic circulation to other viscera. The enzyme nucleosides liberate the free purine and pyrimidine base and ribose or deoxyribose from the nucleosides.

What drugs cause uric acid to be excreted?

1. Uricosuric drugs like salicylates, cinchopher, adrenal cortical hormones, which cause increased excretion of uric acid in urine by decreasing its re-absorption. 2. Allopurinol (Allantoin) a structural analogue to hypoxanthine which competitively inhibits xanthine oxidase and decreases the production of uric acid.

Where are pyrimidine nucleosides catabolized?

Pyrimidine nucleosides are catabolized in the liver. The products of breakdown of pyrimidine ring are ammonia and CO 2 which are converted into urea for excretion.

What is the primary structure of a nucleic acid?

Primary Structure of Nucleic Acids . • The primary structureof a nucleic acid is the nucleotide sequence • The nucleotides in nucleic acids are joined by phosphodiester bonds • The 3’-OH group of the sugar in one nucleotide forms an ester bond to the phosphate group on the 5’-carbon of the sugar of the next nucleotide .

What protein prevents the synthesis of lactose enzymes?

produces a repressor proteinthat prevents the synthesis of lactose enzymes - the repressor turns off mRNA synthesis

Which enzyme catalyzes the formation of 5’-3’ester bonds of the cytoplasm?

polymerasecata lyzes the formation of 5’-3’ester bonds of the

What is the secondary structure of DNA?

Secondary Structure: DNA Double Helix . • In DNA there are two strands of nucleotides that wind together in a double helix. - the strands run in opposite directions - the bases are are arranged in step-like pairs - the base pairsare held together by hydrogen bonding • The pairing of the bases from the two strands is very specific • The ...

What are the two types of nucleic acids?

Also during this period, it was shown that two types of nucleic acid occur in cells: deoxy­ribonucleic acid and ribonucleic acid (RNA).

What substance was responsible for the transformations observed by Griffith and Alloway?

The substance responsible for the transformations observed by Griffith and Alloway (called “transform­ing principle ”) was finally identified in 1944 by 0. T. Avery, C. M. MacLeod, and M. McCarty. Although crude extracts of heat-killed S cells were found to con­tain protein, polysaccharide, lipid, and nucleic acid, the removal of the protein, polysaccharide, and lipid by a combination of chemical and enzymatic proce­dures, including enzymatic hydrolysis, chloroform extraction, and alcohol fractionation, resulted in a product that retained the transforming activity.

What was used to separate the attached viruses from the E. coli culture?

Following lysis of the bac­terial cells, the 35 S-labeled viruses were collected and used to infect E. coli cultured on media devoid of 35 S. A Waring blender was then used to separate by physi­cal agitation what was left of the attached viruses from the surfaces of the bacterial hosts.

Is DNA present in the nucleus of an organism?

These analyses revealed that the amount of DNA per cell was more or less con­stant within the various tissues of an organism. More­over, it was also found that the total quantity of DNA present in the cell nucleus was related to its ploidy (i.e., the number of complete sets of chromosomes). The gametes (sperm and egg cells) of an organism were shown to have one-half as much DNA as the dip­loid somatic cells. This is precisely what would be ex­pected if DNA served as the genetic material.

Is the nucleic acid the same as the protein of the hybrid viruses?

It was not the same as the protein of the hybrid viruses causing the infection. These obser­vations support earlier conclusions concerning the ge­netic role of the nucleic acids and also prove that these molecules alone contain information that determines the specific nature of newly synthesized protein.

Overview

Synthesis of nucleic acids

Degradation of nucleic acids

Interconversion of nucleotides

See also

External links