BioChem (Nucleic Acids)
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School
Arellano University, Pasig**We aren't endorsed by this school
Course
NURSING 156
Subject
Biology
Date
Dec 16, 2024
Pages
8
Uploaded by GrandRain13191
BiochemistryLesson : Nucleic AcidsWhat Are Nucleic Acids Made Of?●The main function of the nucleic acid is forheredity, storage of genes or geneticmaterials.●What are the molecules of the chemicalcomponent of nucleic acid and there aretwo kinds of nucleic acids are found in thecells:○Ribonucleic Acid (RNA) andDeoxyribonucleic Acid (DNA) thatcan be found in nucleus. There isRNA in the cytoplasm of the cellbecause it has ribosomes.○Both DNA and RNA are polymers○The building blocks of nucleic acidchains are the nucleotides○Nucleotides themselves, howeverare composed of three simplerunits: a base, a sugar, and aphosphate group●The sugar component in nucleotide is amonosaccharide, either a Ribose (RNA) orDeoxyribose (DNA)●Two types of bases: Purines (Adenine (A),and Guanine (G)) Pyrimidines (Cytosine(C), Thymine (T), and Uracil (U))Nitrogen Containing Heterocyclic Bases●All are aromatic amines●Adenine ( A ) and guanine ( G) arepurines; cytosine ( C), thymine ( T ) anduracil ( U) are pyrimidines●Adenine, Guanine and Cytosine are foundin both DNA and RNA, but Uracil is foundonly in RNA and Thymine is found only inDNAPurine Structure●A bicyclic (meaning: presence of twocyclic form) base with fused five and sixmembraned rings●2 purine derivatives: adenine and guanineadenine is the 6-amino derivative andguanine is the 2-amino-6-oxo purinederivative●The presence of an amino group and anoxo group in Adenine and Guanine.Pyrimidine Structure1
●A monocyclic base with a 6 membranedring●Derivatives are the thymine, Cytosine andUracil●Thymine is the 5 methyl -2,4 dioxoderivative●Cytosine is the 4-amino-2-oxo derivative●Uracil is the 2,4 dioxo derivativePentose Sugar●The sugar component of RNA is D- riboseand in the DNA is 2-deoxy-D- ribose (it isin the 2nd carbon atom the removal ofoxygen, this is the difference between thetwo)●Pentose is a monosaccharide and a has 5carbon atomPhosphate●Derived from phosphoric acid ( H3PO4 )●The phosphoric acid loses two of itshydrogen atoms to give a hydrogenphosphate ion ( HPO4¯)Nucleoside Formation●Important characteristics of the nucleosideformation process of combining twomolecules into one (combined ofnitrogenous bases and sugar component —base + sugar = nucleoside, without thephosphate group) it is through thehydrolysis reaction, a nucleoside formswhen a sugar combines with a base whichis through the glycosidic bond.●Two important characteristics of thenucleoside formation process combiningtwo molecules into one.1.The base is always attached to C1’of the sugar which is always in a βconfiguration2.A molecule of water is formed asthe two molecules bond togetherand condensation reaction occurs2
The Eight Nucleoside and Nucleotides in DNAand RNANucleotide Formation●Formation of nucleotide from a sugar, abase and a phosphate can be visualized asa two step process:○First the pentose sugar and nitrogencontaining base react to form atwo- subunit entity called aNUCLEOSIDE. What carbon atomdoes the nitrogenous base attach inpentose sugar?○The nucleoside reacts with aphosphate group to form the threesub unit entity called aNUCLEOTIDE. The nucleotideforms with the OH hydroxyl groupof your carbon 5 sugar in anucleoside bond in the hydrogenphosphate.●Important characteristics of the nucleotideformation process by adding a phosphategroup to a nucleoside are the following:○The phosphate group is attached tothe sugar at the C5’ positionthrough a phosphoester linkage.The C1 is through glycosidiclinkage.○As with nucleoside formation, amolecule of water is produced innucleotide formation. Thus, overalltwo molecules of water areproduced in combining a sugar,base and phosphate into anucleotide.○But if you have only the formationof base and sugar, isang watermolecule lang. But if the sugar isbonded into a phosphate group youhave an addition of anothermolecule.●DNA is only confined in the nucleus, whileRNA Rna can be seen in nucleus andcytoplasm.●The only difference between DNA andRNa is in C2 because of the removal ofOxygen atoms in RNA.Primary Nucleic Acid Structure●Each non terminal phosphate group of thesugar phosphate backbone is bonded to3
two sugar molecules through a 3’ , 5’phosphodiester linkage . There is aphosphoester bond to the 5’ carbon of onesugar unit and a phosphoester bond to the3’ carbon of the other sugar●There's 4 nucleotides. The backbone ofDNA contains an alternating Deoxyriboseand the phosphate group. They are not onthe same level. Each phosphate group islinked to carbon number 3 of onedeoxyribose unit, and this is linked toanother phosphate group of the nucleotide.This is linked to phosphoester linkage.●A nucleotide chain has directionality. Oneend of the nucleotide chain, the 5’ endnormally carries a free phosphate groupattached to the 5’ carbon atom. The otherend of the nucleotide chain, the 3’ endnormally has a free hydroxyl groupattached to the 3’ carbon atom.●Each nonterminal phosphate group in thebackbone of a nucleic acid carries 1-charge.Three parallels between primary nucleic acidstructure and primary protein structure are worthnoting:●DNAs and RNAs and proteins all havebackbone that do not vary in structure●The sequence of attachments to thebackbone ( nitrogen bases in nucleic acidsand amino acid R groups in proteins )distinguishes one DNA from another , oneRNA from another and one protein fromanother.●Both nucleic acid polymer chains andprotein polymer chains have directionality: for nucleic acids, there is a 5’ enlThe DNA (Double Helix)●The DNA double helix involves twopolynucleotide strands coiled around eachother in a manner somewhat like a spiralstructure.●Double helix structure is made up of twopolynucleotide●Yung phosphate group yung nakapaikot isthe nucleoside which is the nitrogenousbases and the sugar. Nitrogenous basesyung nasa gitna●The quantity of nitrogenous bases isalways equal in the quantity in other based●The double helix of DNA is through thehydrogen bond linking the two bases, hindigaanong ka-strong yung bond na ‘to, soyung amino acid ng proteins determine theother of the bases that provide the primarystructure of the DNA●Laing 5’ to 3’4
Base Pairing●Always equal quantity ang nag-ppair samga base●The base sequence of a single strand of aDNA molecule segment is always writtenin a direction from the 5’ end to the 3’ endof the segment.5’ A-A-G-C-T-A-G-C-T-T-A-C-T 3’Predicting Base Sequence in a ComplementaryDNA strand●Predict the sequence of bases in the DNAstrand that is complementary to the DNAstrand shown5’ C-G-A-A-T-C-C-T-A 3’●Solution: Because only A forms acomplementary base pair with T and onlyG with C , the complementary strand is asfollow3’ G-C-T-T-A-G-G-A-T 5’●Note the reversal of the numbering of theends of the complementary strandcompared to the given strand. This is dueto the antiparallel nature of the two strandsin a double helix.Replication of DNA Molecules●DNA REPLICATION is the biochemicalprocess by which DNA molecules produceexact duplicates of themselves●It takes place during in the Interphase (Sphase)●There is a presence of the enzymes(Helicase) that initiates the DNAreplication, and it also initiates theuncoiling of the strands in DNA●DNA replication usually occurs at multiplesites within a molecule5
Ribonucleic Acid●Four Major Differences Exist BetweenRNA molecules and DNA molecules:1.The sugar unit in the backbone ofRNA is ribose; it is deoxyribose inDNA.2.The base thymine found in DNA isreplaced by uracil in RNA. InRNA, uracil instead of thymine,pairs with adenine.3.RNA is a single stranded molecule;DNA is double stranded.4.RNA molecules are much smallerthan DNA molecules, ranging from75 nucleotides to a few thousandnucleotides.Types of RNA Molecules●Heterogeneous nuclear RNA ( hnRNA)○An RNA formed directly by DNAtranscription○Nuclear product is heterogeneousin size and very large●Messenger RNA ( mRNA)○An RNA that carries instructionsfor protein synthesis (GENETICINFORMATION) to the sites forprotein synthesis○This is the RNA that is carriedfrom the nucleus papunta saribosome.●Small nuclear RNA ( snRNA )○An RNA that facilitate theconversion of heterogeneousnuclear RNA to messenger RNA○contains from 100 to 200nucleotides○Sila yung nag-pprocess ng initialmessenger RNA to each matureformed.●Ribosomal RNA ( rRNA)○an RNA that combines withspecific proteins to formribosomes.6
●Transfer RNA ( tRNA)○An RNA that delivers amino acidsto the sites for protein synthesis○The smallest of the RNAspossessing only 75-90 nucleotides●Micro RNA ( miRNA)○An RNA that inhibits translation ofmRNA into protein and promotesthe degradation of mRNA .○They do affect gene expressiongrowth which is important in thedevelopment or growth of theRNA.●Small Interfering RNA ( siRNA)○An RNA that have been found tohave a control in gene expression○It also affects gene expression.Being used in the splicing the skins●Long Non Coding RNA (lncRNA)○An RNA that is used to silence aspecific chromosomes○Others have shown to play a role inactivating specific genes●Piwi-associated RNA ( piRNA)○An RNA that is used to bind to andlead to the destruction oftransposons (said to be a DNAsegment that can be moved aroundthe genome)○Some referred this as the genome’sown immune system●Circular RNA○Acts as miRNA sponge, thuscontrolling the effects of miRNATranscription: RNA Synthesis●Transcription is the process by whichDNA directs the synthesis of hnRNA /mRNA molecules that carry the codedinformation needed for protein synthesis●Within the strand of DNA there isconstruction, it is used for the replication.Just to produce proteins●During transcription a DNA moleculestends to unwinds (uncoiling) is under theinfluence of the enzymes (helicase)Steps in Transcription Process1.A portion of the DNA double helixunwinds, exposing a sequence of bases ( agene) . The unwinding process is governedby the enzyme RNA polymerase ratherthan a DNA helicase2.Free ribonucleotides , one nucleotide at atime , align along one of the exposedstrands of DNA bases, the template strand,forming new bases pairs3.RNA polymerase is involved in thelinkage of ribonucleotides,one by one , tothe growing hnRNA molecule4.Transcription ends when RNA polymeraseenzymes encounter a sequence of basesthat is “read “ as a stop signal. The newlyformed hnRNA molecule and RNApolymerase enzyme are released and theDNA then rewinds to reform the originaldouble helix●Exon - a gene segment that conveysgenetic information●Intron- a gene segment that does notconvey for genetic information●Splicing - the process of removing intronsfrom hnRNA molecule and joining the7
remaining exons together to form anmRNA moleculeTransfer RNA (tRNA)●Transfer of amino acids in proteinsynthesis, a presence of codons.Two features of tRNA structure1.The 3’ end of the open part of thecloverleaf structure is where an amino acidcovalently bonds to tRNA. The carboxylgroup of the amino acid reacts with the 3’OH group of the terminal nucleotideresidue resulting in the formation of anaminoacyl ester2.The loop opposite the open end of thecloverleaf called the anticodon loopconsists of seven unpaired bases of whichthe middle three bases constitute theanticodon . These anticodon recognizesand base pairs with an mRNA codon thatpossesses a complementary three baseunit.Interaction between the anticodon (tRNA)and codon (mRNA)Translation: Protein Synthesis●Translation is the process by which mRNAcodons are deciphered and a particularmolecule is synthesized8