lecture 28 - Chapter 28. Biomolecules: Nucleic Acids Based...

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Chapter 28. Biomolecules: Nucleic Acids Based on McMurry’s Organic Chemistry , 7 th edition
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2 Nucleic acids DNA and RNA are chemical carriers of a cell’s genetic information Coded in a cell’s DNA is the information that determines the nature of the cell, controls cell growth, division Nucleic acid derivatives are involved as phosphorylating agents in biochemical pathways
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3 Why this Chapter? Last, but not least of the 4 major classes of biomolecules to be introduced To introduce chemical details of DNA sequencing and synthesis
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4 28.1 Nucleotides and Nucleic Acids Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are the chemical carriers of genetic information Nucleic acids are biopolymers made of nucleotides, aldopentoses linked to a purine or pyrimidine and a phosphate RNA is derived from ribose DNA is from 2 -deoxyribose (the ' is used to refer to positions on the sugar portion of a nucleotide)
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5 Heterocycles in DNA and RNA Adenine, guanine, cytosine and thymine are in DNA RNA contains uracil rather than thymine
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6 Nucleotides In DNA and RNA the heterocycle is bonded to C1 of the sugar and the phosphate is bonded to C5 (and connected to 3’ of the next unit)
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7
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8 Nucleotides join together in DNA and RNA by as phosphate between the 5’-on one nucleotide and the 3 on another One end of the nucleic acid polymer has a free hydroxyl at C3 (the 3 end), and the other end has a phosphate at C5 (the 5 end).
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9 28.2 Base Pairing in DNA: The Watson–Crick Model In 1953 Watson and Crick noted that DNA consists of two polynucleotide strands, running in opposite directions and coiled around each other in a double helix Strands are held together by hydrogen bonds between specific pairs of bases Adenine (A) and thymine (T) form strong hydrogen bonds to each other but not to C or G Guanine (G) and cytosine (C) form strong hydrogen bonds to each other but not to A or T
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10 Hydrogen Bonds in DNA The G-C base pair involves three H-bonds The A-T base pair involves two H-bonds
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11 The Difference in the Strands The strands of DNA are complementary because of H-bonding Whenever a G occurs in one strand, a C occurs opposite it in the other strand When an A occurs in one strand, a T occurs in the other
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12 Grooves The strands of the DNA double helix create two continuous grooves (major and minor) The sugar–phosphate backbone runs along the outside of the helix, and the amine bases hydrogen bond to one another on the inside The major groove is slightly deeper than the minor groove, and both are lined by potential hydrogen bond donors and acceptors.
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This note was uploaded on 09/06/2009 for the course CHEM chem 12 AB taught by Professor Adamczeski during the Spring '09 term at San Jose City College.

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lecture 28 - Chapter 28. Biomolecules: Nucleic Acids Based...

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