Nucleic Acids

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Nucleic Acids
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Role of nucleic acids in cells
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• A nucleic acid is composed of a long string of
  nucleotides
• A NUCLEOTIDE consists of
• a N containing base
• a 5C sugar (pentose)
• an inorganic phosphate group

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nucleotide chemical structure
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nucleotide simplified structure
P
sugar
base
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There are 5 different basesadenine, cytosine,
guanine, thymine and uracil
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• Nucleotides join together by a condensation
  reaction
• An ester bond forms
  between the
  phosphate group of
  1 nucleotide
  and the sugar group
  of another
  forming a
  polynucleotide

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DNA

• DNA nucleotides are made up of
• 1 phosphate group
• 5C sugar deoxyribose
• 1 base of 4 thymine
  cytosine guanine
  adenine

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• DNA is a double helix
• It is made up of 2 strands joined together by
  H-bonds between the bases
• They join A-T C-G

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• A forms 2 H bonds with T
• G forms 3 H bonds with C
• The specific pairing of bases is called
  complementary base pairing.
• There will always be the same number of
  complementary bases AT GC
• So the number of purines (A, G) will always be
  equal to the number of pyrimidines (C,T)

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The strands are ANTI-PARALLELThis means the 2
strands run in opposite directionsThe
sequence of bases makes up the genetic code
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RNA

• RNA nucleotides are made up of
• 1 phosphate group
• 5C sugar Ribose
• 1 base of 4 uracil
  cytosine guanine
  adenine

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• RNA polynucleotides are single stranded
• There is no
  relationship between
  the
  number of purines
  and pyrimidines.

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• There are three main types of RNA
• mRNA messenger RNA
• formed in nucleus during transcription, carries
  genetic code into the cytoplasm
• rRNA ribosomal RNA
• Made in nucleolus , forms ribosomes, site of
  protein synthesis
• tRNA transfer RNA
• found in the cytoplasm, transports amino acids to
  the ribosomes during translation

More detail to follow at A2!!!
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Differences between DNA RNA


DNA
RNA