ch25 - Chapter 25 Nucleic Acids and Protein Synthesis...

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Chapter 25 Nucleic Acids and Protein Synthesis
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Chapter 25 2 Introduction Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the molecules that carry genetic information in the cell DNA is the molecular archive for protein synthesis RNA molecules transcribe and translate the information from DNA so it can be used to direct protein synthesis DNA is comprised of two polymer strands held together by hydrogen bonds Its overall structure is that of a twisted ladder The sides of the ladder are alternating sugar and phosphate units The rungs of the ladder are hydrogen-bonded pairs of heterocyclic amine bases
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Chapter 25 3 DNA polymers are very long molecules DNA is supercoiled and bundled into 23 chromosomes for packaging in the cell nucleus The sequence of heterocyclic amine bases in DNA encodes the genetic information required to synthesize proteins Only four different bases are used for the code in DNA A section of DNA that encodes for a specific protein is called a gene The set of all genetic information coded by the DNA in an organism is its genome The set of all proteins encoded in the genome of an organism and expressed at any given time is its proteome The sequence of the human genome is providing valuable information related to human health Example: A schematic map of genes on chromosome 19 that are related to disease
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Chapter 25 4 Nucleotides and Nucleosides Mild degradation of nucleic acids yields monomer units called nucleotides Further hydrolysis of a nucleotide yields: A heterocyclic amine base D-ribose (from RNA) or 2-deoxy-D-ribose (from DNA); both are C5 monosaccharides A phosphate ion The heterocylic base is bonded by a β N -glycosidic linkage to C1’ of the monosaccharide Examples: A general structure of an RNA nucleotide (a) and adenylic acid (b) A nucleoside is a nucleotide without the phosphate group A nucleoside of DNA contains 2-deoxy-D-ribose and one of the following four
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Chapter 25 5 A nucleoside of RNA contain the sugar D-ribose and one of the four bases adenine, guanine, cytosine or uracil
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Chapter 25 6 Nucleosides that can be obtained from DNA
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Chapter 25 7 Nucleosides that can be obtained from RNA
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Chapter 25 8 Nucleotides can be named in several ways Adenylic acid is usually called AMP (adenosine monophosphate) It can also be called adenosine 5’-monophosphate or 5’-adenylic acid Adenosine triphosphate (ATP) is an important energy storage molecule The molecule 3’,5’-cyclic adenylic acid (cyclic AMP) is an important regulator of hormone activity This molecule is biosynthesized from ATP by the enzyme adenylate cyclase
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Chapter 25 9 Laboratory Synthesis of Nucleosides and Nucleotides Silyl-Hilbert-Johnson Nucleosidation An N -benzoyl protected base reacts with a benzoyl protected sugar in the presence of tin chloride and BSA (a trimethylsilylating agent) The trimethylsilyl protecting groups are removed with aqueous acid in the 2nd step The benzoyl groups can be removed with base
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ch25 - Chapter 25 Nucleic Acids and Protein Synthesis...

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