1- Nucleotides

• Nucleotide


  A molecule consisting of a 5-carbon sugar, a phosphate group, and a nitrogenous base
• Nucleotides found in DNA and RNA

  • Contain a 5-carbon sugar (deoxyribose in DNA, ribose in RNA)
  • Contain a phosphate group
  • Contain a nitrogenous base (adenine, thymine, guanine, cytosine in DNA; adenine, guanine, cytosine, uracil in RNA)
• Formation of a polynucleotide

  1. Two nucleotides form a phosphodiester bond between the phosphate group of one and the hydroxyl group on carbon 3 of the other

  2. This releases water, a condensation reaction

  3. Repeating this forms a polymer of nucleotides, called a polynucleotide
• Breaking a phosphodiester bond


  Requires adding water, a hydrolysis reaction
• DNA and RNA are examples of polynucleotides
• Purines (adenine, guanine) have a double ring structure, pyrimidines (thymine, cytosine, uracil) have a single ring structure
• RNA contains uracil instead of thymine