UT Knoxville BIOL 140 - Chapter 4 (31 pages)

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Chapter 4



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Chapter 4

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Pages:
31
School:
University of Tennessee
Course:
Biol 140 - Organization/Function of Cell
Organization/Function of Cell Documents

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CHAPTER 4 2011 Pearson Education Inc What Is a Nucleic Acid A nucleic acid is a polymer of nucleotide monomers Nucleotides are each composed of a phosphate group a sugar and a nitrogenous base The sugar is ribose in ribonucleotides and deoxyribose in deoxyribonucleotides There are two groups of nitrogenous bases purines adenine guanine pyrimidines cytosine uracil and thymine Uracil U is found only in ribonucleotides and thymine T is found only in deoxyribonucleotides 2011 Pearson Education Inc 2011 Pearson Education Inc 2011 Pearson Education Inc 2011 Pearson Education Inc Could Chemical Evolution Produce Nucleotides Simulations of chemical evolution have not yet produced nucleotides Sugars and purines are easily made but pyrimidines and ribose are not easily synthesized Ribose problem Ribose would have had to have been dominant on ancient Earth for nucleic acids to form 2011 Pearson Education Inc Nucleotides Polymerize to Form Nucleic Acids Nucleic acids form when nucleotides polymerize A condensation reaction forms a phosphodiester linkage phosphodiester bond between the phosphate group on the 5 carbon of one nucleotide and the OH group on the 3 carbon of another Types of nucleotides involved Ribonucleotides which contain the sugar ribose and form RNA Deoxyribonucleotides which contain the sugar deoxyribose and form DNA 2011 Pearson Education Inc 2011 Pearson Education Inc The Sugar Phosphate Backbone Is Directional The sugar phosphate backbone of a nucleic acid is directional one end has an unlinked 5 carbon and the other end has an unlinked 3 carbon The nucleotide sequence is written in the 5 3 direction This reflects the sequence in which nucleotides are added to a growing molecule This nucleotide sequence comprises the nucleic acid s primary structure 2011 Pearson Education Inc 2011 Pearson Education Inc The Polymerization of Nucleic Acids Is Endergonic Polymerization of nucleic acids is an endergonic process catalyzed by enzymes Energy for polymerization



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