Structure of nucleotides and nucleic acids

• what is DNA?

  • deoxyribonucleic acid
  • almost all found in nucleus of eukaryotic cells
  • an information store
• what is RNA?

  • ribonucleic acid
  • 3 different forms
  • needed to translate the code from DNA to make proteins
• what are the three components of a nucleotide?

  • an inorganic phosphate group
  • a pentose sugar (either ribose or deoxyribose)
  • a nitrogen-containing base
• how is the structure of ribose different to the structure of deoxyribose?

  deoxyribose doesn’t contain an oxygen in its carbon 2, just a hydrogen
• what are the purine bases?

  • adenine
  • guanine
• what are the pyrimidine bases?

  • thymine
  • cytosine
  • uracil
• what bases are present in DNA?

  • adenine
  • guanine
  • thymine
  • cytosine
• what bases are present in RNA?

  • adenine
  • guanine
  • cytosine
  • uracil
• how do you remember the sizes of the bases?

  • purine is a small name, but they have larger structures
  • pyrimidine is a larger name, but they have small structures
• what type of reaction join the three components together?

  condensation
• what does ADP stand for?

  adenosine diphosphate
• what is the name of the bond joining nucleotides together?

  phosphodiester bonds - between sugar and phosphate
• how are phosphodiester bond formed?

  • phosphate group at carbon 5 of the pentose sugar of one nucleotide forms a covalent bond with the hydroxyl (OH) group at carbon 3 of the pentose sugar of an adjacent nucleotide
• how is a phosphodiester bond broken?

  hydrolysis
• compare RNA and DNA

  • DNA will contain Thymine, RNA will contain Uracil in place of T
  • RNA has an oxygen on ribose, DNA doesn’t (deoxyribose)
  • DNA is a double helix of 2 strands, RNA is 1 strand
• how many strands are there in a DNA molecule?

  2 polynucleotide strands
• what is the name of the coiled DNA shape?

  double helix
• what are the main features of a DNA strand structure?

  • nitrogen-containing bases
  • sugar-phosphate backbone
  • hydrogen bonds between complementary bases
• how are the nucleotides connected?

  a bond between the phosphate of one nucleotide and the sugar of the next
• what is the meaning of the term “antiparallel”?

  one strand runs the other way round to the second strand
• what base pairs go together?

  • A and T (2 hydrogen bonds)
  • G and C (more H bonds (3))
• what is a hydrogen bond?

  • weak bonds within or between molecules
  • stabilise a molecule or increase its melting and boiling point
  • result from the interaction of polar covalent bonds
• what can you notice about the specific base pairing?

  contains 1 purine and 1 pyrimidine
• how is DNA structure related to its function?

  • are long - large amount of information can be stored
  • base pairing rules mean that complementary strands of information can be replicated
  • double helix - give stability
  • H bonds allow easy unzipping for copying and reading information