Chapter 4

Chapter 4 - Chapter 4 Nucleic Acids: The origin of life 4.1...

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Chapter 4 – Nucleic Acids: The origin of life 4.1 – What are the chemical structures and functions of nucleic acids? Nucleic acids are polymers used for the storage, transmission and use of genetic information o DNA – macromolecule to encode hereditary information through RNA Uses pentose deoxyribose o RNA – information goes through RNA to make proteins Uses pentose ribose Nucleic acids are composed of monomers called nucleotides o Nucleotides are made up of a pentose sugar, a phosphate group and a nitrogen containing base Bases of nucleic acids take a purine or a pyramidine Both DNA and RNA have backbone of -pentose-phosphate-pentose-phospate- Sugars and phosphates of the nucleotides are joined via phosphodiester linkages o Diester means two covalent bonds formed by –OH groups reacting with acidic phosphate groups Most RNA contains 1 polynucleotide chain, DNA is double stranded though Two strands of DNA run in opposite direction, hence they are antiparallel, allows 3d structures Adenine and Guanine are purines Thymine and Cytosine are pyrimidines Base pairing (A-T/U) (C-G) is due to o The sites for hydrogen bonding on each base o The geometry of the sugar-phosphate backbone o The molecular sizes of paired bases (larger purines with small pyrimidines is stable) A-T bonds are 2 hydrogen bonds C-G bonds are 3 hydrogen bonds RNA is single stranded, thus it can interact with itself or another DNA strand o The A on an RNA can interact with a T on a DNA or a U on itself Diversity in protein structure reflects diversity in DNA base sequences DNA is a purely informational molecule o
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Chapter 4 - Chapter 4 Nucleic Acids: The origin of life 4.1...

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