Nucleic Acids
August 21, 2022 | Author: Anonymous | Category: N/A
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Description
NUCLEIC ACIDS Nucleic acids are acids are large organic compounds found in the chromosomes of living cells and viruses. They are strong acids found in the nucleus of the cells. The nucleic acid polymers are with high molecular weights as high as 100,000,000 grams per mole. With proteins, nucleic acids acids are are most important biological macromolecules. They are found in abundance in all living cells. History
In 18!, "riedrich #iescher isolated nuclei from pus cell and found that they contained phosphate$rich substance, he named it nuclein. In 18!!, %ltmann, introduced the term nuclei acid. "ischer in the 1880s, discovered purine and acids.. &acharis in the year 1881, identified nuclein with chromatin. In 188', pyramidine bases in nucleic acids (ertwig claimed that nuclein is responsible for the transmission of hereditary characters. In 1!'1, acids were were connected to protein synthesis. In 1!'', +swald )aspersson and *rachet, related that that nucleic acids T. %very, )olin #. #aceod and #aclyn #c)arty, e-perimented that N% is directly involved in inheritance. In 1!/, ames . Watson and "rancis (.). )ric2 constructed the double helical model for the N% molecule.
Nucleic Acid Defnition
acids are essential large biological Nucleic acids are b iological molecules for all forms of life. The nucleic acids include acids include the N% and the 3N%. They are the hereditary determinants of living organisms. They are present in most living cells either in free state or bound to proteins as nucleoproteins. The The nucleic acids acidsare are biopolymers with mononucleotides ad their repeating units. The monomers are 2nown as nucleotides, they are made up of three units4 a sugar, an amine and a phosphate group.
Properties o Nucleic Acids Properties of nucleic acids are acids are as follows: - Nucleic acids (DNA acids (DNA and RNA) are long polymers made of repeating units of nucleotides. - Nucleotide units are made of phosphate-sugar-nitrogenous base units. - he nitrogenous bases found in DNA are adenine! guanine! cytosine and thymine. - Adenine and guanine are purine bases while cytosine and thymine are pyrimidnes. - "n RNA! the thymine bases id replaced by uracil which is also a pyrimidine. - he nucleotides are lin#ed with phosphodiester bonds. - hey are lin#ed by a phosphate group on the $th position of sugar residue becomes lin#ed to %& hydro'yl group of the preceeding sugar molecule. -he double stranded model of the DNA was wor#ed out by atson and ric# in *+$%. - he double heli' model consists of two strands wound around a central a'is with the bases stac#ed inside. -he order of the strand is in opposite directions! i.e.! from $& to %& direction in one and %&to $& direction in the other. -he bases stac#ed in the center of the heli' as they interact with each other through wea# hydrogen bonds. - ,ydrogen bonds are wea#er than coalent bonds! they are continually forming and disassociating. - "n the double stranded nucleic acids acids!! the adenine form hydrogen bonds only with thymine (or uracil) molecule. hile cytidine will only form hydrogen bonds with guanine. - ,ence! in a a gien strand of DNA! the amount of adenine is always eual to the amount of thymine! and the amount of cytidine always euals the amount of guanine! in a gien species. - he per cent of the /- and the A- is ariable from species to species. - he base pairs form a 0at plain in the heli'! the adenine forming two hydrogen bonds with thymine!
and the cytidine cytidine forming three three bonds bonds with guanine. guanine. - 1sing the concept of base pairing! all the en2ymes and substrates necessary! the two DNA strands when copied separately! whereer there is adenine in the original strand! the duplicated strand will hae thymidine! and guanine would be matched to cytosine. - After replication! each original strand (parent strand)! is paired with a new (daughter) strand. his type of replication is #nown as semi-conseratie semi-conseratie mode of duplication. -he double stranded DNA can be denatured by al#aline conditions or heat. - 3mall stretches of polynucleotides will anneal to larger single stranded DNA molecule if the DNA seuence matches! by base pairing.
Types o Nucleic Acids Nucleic acids are acids are of two types N% and 3N%
DNA (deoxyribonucleic acid)
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N% is one of the macromolecules, they are essential to all living forms.
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eo-yr eo -yrib ibonu onucle cleic ic acid acid contai contains ns the gen geneti etic c inf inform ormati ation, on, it is used used in the develo developme pment nt and functioning of all living organisms.
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The N% segments carry genetic information are called the genes.
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+ther N% segments have structural functions or regulate the genetic information.
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N% are made of two chains made of polymer units of nucleotides. The bac2bones of N% are made of sugar and phosphate groups which are 5oined by ester bonds.
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The two strands of N% are anti$parallel, they run in opposite directions.
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6ach sugar molecule is attached to one of the four nucleobases.
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The nucleobases encode genetic information, that is read using the genetic code.
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Inside the cell, the N% are arranged in long structures called chromosomes.
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The chromosomes are duplicated in the process of N% replication, during cell division.
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6ach cell has its own one complete set of chromosomes.
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In eu2aryotic organisms, most N% is stored in the nucleus of the cell, and also some of it in cellular organelles li2e mitochondria or chloroplast.
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The pro2aryotes store the N% in the cytoplasm.
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)hromatin proteins li2e histones compact and organi7e the N%
RNA (ribonucleic acid) •
The functions of ribonucleic acid is to convert genetic information from genes into amino acid seuences of protein.
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In some viruses, 3N% contains the genetic information.
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3N% 3N % is of three three typ types, es, they they are t3N t3N% % 9trans 9transfer fer 3N%: 3N%:,, m3N% m3N% 9me 9messe ssenge ngerr 3N 3N%: %: and r3N% r3N% 9ribosomal 3N%:.
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#essen #es senger ger 3N%, 3N%, as the name name sugges suggests ts acts acts a messen messenger ger.. It car carri ries es gen geneti etic c in infor format mation ion seuences between N% and ribosomes, and it also a lso directs protein synthesis.
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r3N% is a ma5or component of the ribososmes, they cataly7e the formation of peptide bond.
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The t3N% act as a carrier molecule for the amino acids that are used in protein synthesis. The t3N% are also responsible for decoding the m3N%.
Structure o Nucleic Acids ;tructure of nucleic acids N% acids N% and 3N% are similar. The structure is divided into four different levels, primary, secondary, tertiary and uaternary.
Primary Structure . The /$carbon sugar is deo-yribose for N% and and ribose sugar in 3N%. The purine bases, form glycosidic bond between their !? nitrogen and the !? $ +( group of the sugar molecule. The pyrimidine bases, they form glycosidic bond betwe bet ween en 1? nit nitrog rogen en and the !? $+ $+( ( of the deo-y deo-yrib ribose ose.. In bot both h pur purine ine and pyrimi pyrimidin dine e bases bases the phosphate phosp hate group form forms s a bond with the sugar molecule between one of its negativel negatively y charg charged ed o-ygen groups and the /? $+( of the sugar. Nucleotides forms phosphodiester lin2ages between the /? and ?
carbon atoms, these form the nucleic acids acids.. Nucleotides seuences are complementary to one another.
6-ample of complementary seuence %@)T is T)@%.
Secondary Structure ;econdary structure is the interaction between the bases. This structure shows parts of which strands are bound to each other. The two strands of N% in the double heli- of the N% are bound to each other by hydrogen bounds. The nucleotides on one strand base pairs with the nucleotides of the other strand. The secondary structure of the N% is predominantly the base pairing of the two polynucleotide strands forming a double heli-.
ertiary Structure Tertiary structure is the three dimensional shape into which the entire chain is folded. Tertiary structure arrangement differs in four structural forms4 1. eft eft o orr rrig ight ht han hande dedn dnes ess. s. A. en ength gth of the turn turn of of tthe he hel helii-..
. Nu Numb mber er of of base base p pai airs rs per per ttur urn. n. '.
The di differ fference ence in in si7e si7e between between ma5or ma5or a and nd the mino minorr groove. groove.
!uaternary Structure Buaternary structure is the higher$level of organi7ation of the the nucleic acids. acids. This structure refers to the acids with the other molecules. The most commonly seen organi7ation is the interactions of the nucleic acids form of chromatin which shows interaction with small proteins histones.
Functions o Nucleic Acids
4unctions ns of nuclei nu cleic c acids acid s are: 4unctio •
The main functions is store and transfer genetic information.
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To use the genetic information to direct the synthesis of new protein.
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The deo-yribonucleic acid is the storage for place for genetic information in the cell.
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N% controls the synthesis of 3N% in the cell.
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The genetic information is transmitted from N% to the protein synthesi7ers in the cell.
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3N% also directs the production of new protein by transmitting genetic information to the protein building structures.
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The function of the nitrogenous base seuences in the N% bac2bone determines the proteins being synthesi7ed.
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The function of the double helihe li- of the N% is that no disorders occur in the genetic information if it is lost or damaged.
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3N% directs synthesis of proteins.
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m$3N% ta2es genetic message from 3N%.
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t$3N% transfers transfers activated amino acid, to the site of protein synthesis.
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r$3N% are mostly present in the ribosomes, and responsible for stability of m$3N%.
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