L4-6 quiz

• amino acids typically found in beta (hairpin) turns include

  Glycine and Proline
• if a piece of double-stranded DNA is 340 nm long, how many nucleotides does it contain

  2000 (3.4nm for one turn (10 nucleotides), so 1000 nucleotides on each side)
• if the side chain of an amino acid has the pKa of 4 then at pH 5 10% of the side chains would be

  protonated
• in the DNA double helix

  • the sugars are on the outside
  • the CG base pair is more stable than the AT base pair
  • the phosphate groups are on the outside
  • the bases form purine-pyrimidine pairs
• is the unreacted phosphate group on the first or last amino acidof a polypeptide chain

  the first
• is the unreacted carboxylic acid on the first or last amino acid of a polypeptide chain

  the last
• the DNA double helix is stabilised by a mixture of:

  • van der Waals bonds between bases
  • hydrogen bonds between opposite chains
• planar geometry of the peptide bond is due to

  resonance (electron delocalisation)
• (Watson and Crick suggested) complementary base pairing is significant because it suggest:

  a mechanism for copying the DNA
• which amino acids have polar side chains?

  Serine, threonine, asparagine, glutamine, tyrosine, cysteine, histidine.
• histidine residues are important in active sites of enzymes because

  can function as proton donor or acceptor near physiological pH
• the amino acid with a distinct locked structure interrupting alpha helices and beta sheets is _

  proline
• the nucleotides in nucleic acids are linked by _ bonds

  phosphodiester
• when a peptide bond is made, a molecule of _ is also produced

  water