nucleic acids

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  • Created by: samsam001
  • Created on: 21-03-14 20:15
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  • Nucleic acids
    • DNA is deoxyribonucleic acid
      • Its a double stranded molecule made of two nucleotides
    • A DNA nucleotide is made up of a phosphate group, a five carbon sugar called deoxyribsoe and a base.
      • DNA has 4 bases Adenine, guanine,cytosine and thymine
        • A and G are purine bases
        • C and T are pyramid bases
    • The nucleotides are linked strongly by covalent bonds between the phosphate and deoxyribose group.
      • The phosphate groups bond to the carbon 5 and 3 of the deoxyribose ring
    • the two strands are linked to each other by weak hydrogen bonds between the bases.
      • A is always with T and are linked by two hydrogen bonds
      • C and G are linked by 3 hydrogen bonds
    • The two strands of DNA run in opposite directions, this is called anti-parralel and they twist to form a double helix
    • The DNA moleculesin a cell nucleus are replicate before division.
      • 1. the two strands unzip and untwist
        • 2. complimentary free bases then link up to the exposed bases on the strands.
          • 3.they are then linked together by the formation of bonds between their deoxyribose and phosphate groups.this is catalysed by DNA polymerase
            • 4.two new molecules are formed each containing an old and new strand, the process is semi-conservative
    • The sequence off bases in a DNA molecules codes for the sequence of amino acids in a protein to be made on the ribosome's
      • 3 bases code for one amino acid
        • a sequence of DNA nucleotides that codes for one popypeptide is known as a gene
    • RNA is ribonucleicacid, instead of thymine they contain uracil
    • during protein synthesis,an RNA molecule is built up against one of the DNA strands in a gene.
      • The RNA then travels out of the nucleus to a ribosome, where its sequence of bases is used to determine the sequence of amino acids in the polypeptide


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