Mansoura National University L1 Nucleic Acids PDF

Mansoura national university Semester: 1  Nucleic acids Dr/ Mona Elhelaly Elshebeny Lecturer of Medical Biochemistry [email protected]  Learning Outcomes Identify nucleotides and nucleosides nomenclature & structure List functions of nucleotides & their biological...

Mansoura national university Semester: 1  Nucleic acids Dr/ Mona Elhelaly Elshebeny Lecturer of Medical Biochemistry [email protected]  Learning Outcomes Identify nucleotides and nucleosides nomenclature & structure List functions of nucleotides & their biological importance. Recognize DNA structure Recognize RNA structure Recognize types of RNA Identify differences between DNA and RNA  Agenda Nucleotides and nucleosides (nomenclature , structure). Nucleotides of biological importance & their roles. DNA (types ,structure). RNA ( types & structure). Structure /function relation of RNA. Differences between DNA and RNA  Learning outcome 1 Identify nucleotides and nucleosides nomenclature & structure  Nucleic acids They are intracellular components which are required storage , expression of genetic information Include: DNA (deoxyribonucleic acid) RNA (ribonucleic acid) Nucleic acids (DNA & RNA) are long chains of repeated subunits called nucleotides.  Nucleotide Building blocks of DNA and RNA.  Nucleotide Structure 1-Nitrogenous base a-Purines:  adenine(A)  guanine(G) b-Pyrimidine:  cytosine (C)  thymine(T)  uracil(U). 2-Pentose sugar :  Ribose in RNA  2-deoxy-ribose in DNA 3-Phosphate (phosphoric acid )  Nucleoside Nucleosides (bottom) are made of a nitrogenous base, usually either a purine or pyrimidine, and a five-carbon carbohydrate ribose. A nucleotide is simply a nucleoside with an additional phosphate group.  Learning outcome2 Functions of nucleotides & their biological roles.  Functions of nucleotides 1-Building blocks of RNA and DNA. 2-Source of energy : ATP ,GTP act as source of Energy. 3-Mediate action of hormone: c.AMP and c.GMP are second messenger. 4-Co-enzymes: as NAD, FAD, Co- enzyme A.  Functions of nucleotides 5-Activation of chemical compounds:  UDP-glucose synthesis of glycogen.  CDP choline , CDP-ethanolamine synthesis of phospholipids. 6-Chemical group donors :  PAPS is a sulfate donor synthesis of sulfolipids.  SAM is a methyl donor trans methylation reactions. 7-Synthetic Analogue: nucleotides analogues are prepared by altering the base ring or sugar part. Anti-cancer 5-flurouracil (pyrimidine analogue): ↓ thymine synthesis ↓DNA synthesis ↓growth of cancer cells. Anti-gout Allopurinol (hypoxanthine analogue) used for treatment of gout  Learning outcome 3 Recognize DNA structure DNA (deoxyribonucleic acid) Def : is a very large molecule made up of a long chain of sub-units. The sub-units are called nucleotides The basic shape is like a twisted ladder This is called a double helix.  DNA structure  DNA is 2 strands of polynucleotides ( d.AMP, d.GMP, d.TMP, d.CMP)  The nucleotides are linked by 3`, 5` phosphodiester bond between 3`-(OH) of one nucleotide and 5`phosphate group of next nucleotide.  One strand of DNA has many millions of nucleotides. THE DOUBLE HELIX The paired strands are bases coiled into a spiral called A DOUBLE HELIX sugar-phosphate chain The 2 strands of the double helix are antiparallel (they run in the opposite direction): One runs in the 5`to 3`direction. The other runs in the 3`to 5` direction.  Base Pairing Rule(Chargaff’s Rule) Adenine must pair with Thymine Guanine must pair with Cytosine Their amounts in a given DNA molecule will be about the same. Adenine forms a bond with Thymine Adenine Thymine and Cytosine bonds with Guanine Cytosine Guanine  Ribose is a sugar, like glucose, but with only five carbon atoms in its molecule. Deoxyribose is almost the same but lacks one oxygen atom  Characters of the DNA structure 1-Alternating Sugar-phosphate forms asymmetrical backbone. 2-Nitrogenous bases are projecting to inside of the 2 stands, with right angle 3-Polarity:each strand has 2 ends, one end (5`end) with free phosphate and the other (3`end) with free (OH). 4-The sequence of bases determines the coding structure of DNA ( genetic information) 5-DNA sequences are written in the 5` to 3` ( ex:-5` GCATAACGCCAA 3`).  PO4 PO4 adenine thymine PO4 PO4 cytosine guanine PO4 PO4 PO4 PO4 2-stranded DNA PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4  Functions of DNA DNA is responsible for the storage and transfer of genetic information. It is the carrier of genetic information stored in the nucleotide sequence. It has 2 important functions: 1. direct its own replication during cell division. 2. direct the synthesis of RNA (Transcription). The strands separate during replication PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4  Each strand builds up its partner by adding the appropriate nucleotides PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 Structural forms of the double strand heliex  Learning outcome 4 Recognize RNA structure  RNA (Ribonucleic acid) RNA are Single strand polyribonucleotides. They contain 4 types of nucleotides:  AMP  GMP  CMP  UMP. The nucleotides are linked together by 3`,5` phosphodiester bonds (as DNA). RNA molecules are formed in the nucleus by transcription.  Learning outcome 5 Recognize types of RNA  Types of RNA 1-Messenger RNA (mRNA) : 5 % of cellular RNA 2-Transfer RNA (tRNA) : 15 % of cellular RNA 3-Ribosomal RNA (rRNA): 80 % of cellular RNA 4-Small nuclear RNA (snRNA) : less than 1 % of cellular RNA  Messenger RNA ( mRNA ) -5%of cellular RNA -it carries message from DNA to ribosome where it directs synthesis of specific protein. -each protein has specific mRNA  Ribosomal RNA  Forms about 80 %of total RNA.  It is associated with several proteins to form ribosome  Transfer RNA (t.RNA) 15 %of total RNA It is folded upon itself like a hairpin→ clover-leaf appearance. this structure is stabilized by hydrogen bonds between complementary bases (A=U) , (GΞC). The acceptor arm does not end in a loop. It ends in the sequence CCA-3’that can accept an amino acid, and hence its name. The anticodon arm ends in a loop that contains 7 bases. The 3 bases in the middle of the loop constitute the “anticodon “, and hence its name.  Learning outcome 6 Recognize diffrences between DNA and RNA  DNA RNA Site Nucleus & mitochondria Cytoplasm mainly Fun Storage and transfer of genetic Protein biosynthesis characters Bases A, G, C and T A, G, C and U Sugar Deoxy-ribose Ribose strands 2 strands =double helix One strand Types One type 4 types: 3 forma(A,B,Z) mRNA, tRNA, rRNA, snRNA