Nucleic Acids

• There are two types of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
• The sequence of bases in DNA codes for the sequence of amino acids in a protein. Proteins determine all the characteristics of an organism. RNA molecules are used in protein synthesis.
• Nucleic acids are made from monomers called nucleotides. These have three components:

  1. Phosphate group- found in both DNA and RNA
  2. Pentose (5C) carbon sugar- DNA contains deoxyribose, whilst RNA contains ribose.
  3. Nitrogen containing base- Adenine, Thymine, Uracil, Guanine, Cytosine
• The complementary base pairing rule:

  • Adenine is able to base pair through 2 hydrogen bonds with Thymine (or Uracil in RNA)
  • Guanine is able to base pair through 3 hydrogen bonds with Cytosine.
• Nucleotides link together to form polynucleotides through condensation reactions. A covalent bond called a phosphodiester bond is formed between the Carbon 3 of one nucleotide and the phosphate of another nucleotide. This bonding forms the sugar-phosphate backbone.
• A nucleotide is a monomer made up of a phosphate group, a pentose sugar and a nitrogenous base

  A) Phosphate

  B) Five-carbon Sugar

  C) Nitrogen containing Base

  D) 1

  E) 3

  F) 5