Nucleic Acid Chemistry Lecture Notes PDF

Nucleic acid chemistry  Learning outcomes By the end of lecture, students should be able to: ❖Define nucleic acids ❖Identify the basic structure of nucleotides and nucleosides ❖List nucleotides of biological importance & their roles  Basic of Nucleic acid...

Nucleic acid chemistry  Learning outcomes By the end of lecture, students should be able to: ❖Define nucleic acids ❖Identify the basic structure of nucleotides and nucleosides ❖List nucleotides of biological importance & their roles  Basic of Nucleic acid structure Nucleic acids (DNA & RNA) are long chains of repeated subunits (polymers) of nucleotides.  Nucleotide Structure A nucleotide consists of 3 components: 1- Nitrogenous base 2- Pentose sugar 3- One or more Phosphate group Nucleoside Nucleotide  1- Nitrogenous Bases Purines (both are in DNA & RNA) Adenine Guanine. Pyrimidines: Cytosine (DNA&RNA) Thymine (DNA) Uracil (RNA)  2- Sugars Deoxyribose (forming deoxyribonucleotides) in DNA Ribose (forming ribonucleotides) in RNA  Nucleoside = Sugar + Base Addition of base to the C1 of the pentose sugar produce nucleoside [Glycosidic bond] If ribose (ribonucleoside) If deoxyribose(deoxyribonucleoside)  3- Phosphate phosphate is added C5 to of the pentose The phosphate group is attached by ester bond. Nucleotide = Nucleoside + Phosphate  Functions of nucleotides 1- Building blocks of DNA & RNA 2- Source of energy : ATP ,GTP  Functions of nucleotides 3-Mediate action of hormone : e.g. c.AMP and c.GMP are second messenger 4- Co-enzymes : as NAD, FAD.  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 ------ transmethylation reactions Adenine ribose Methionine ( CH3) 7- Synthetic Analogue: Nucleotides analogues are prepared by altering the base ring or sugar part. Used as drugs in clinical therapy Treatment of Gout -Allopurinol (purine analogue) used for treatment of gout It inhibits xanthine oxidase enzyme Decrease uric acid synthesis  Anti-Tumor (chemotherapy) - 5 flurouracil (pyrimidine analogue) - 6-mercaptopurine (purine analogue) These compounds inhibit the growth of rapidly growing cancer cells by inhibiting the synthesis of DNA & RNA  Case scenario A 44 years old male patient. He was presented with severe pain in his right big toe, with inflammation of the joints. He was diagnosed as acute gouty arthritis. He had been taking allopurinol. 1- Explain chemical nature of allopurinol ? Purine analogue. 2- Explain mechanism of action of allopurinol ? Inhibit xanthine oxidase →↓ production of uric acid. Assessment Which of the following is considered a nucleoside? a) Adenine b) Adenine and ribose c) Adenine, ribose and one phosphate group d) Adenine, ribose and two phosphate group e) Adenine, ribose and three phosphate groups. In nucleotides, phosphate is attached to sugar by: a) Salt bond b) Hydrogen bond c) Ester bond d) Glycosidic bond e) Ionic bond Which of the following nucleotide act as second messenger for hormone? a) UDP b) SAM c) PAPS d) C.AMP e) ATP Which one of the following is a purine base analogue? a) arabinose b) allopurinol c) 5-flurouracil d) 5- odouracil e) pseudouridine