Nucleotides

• nucleotide

  the monomer from which nucleic acids are made from
• nucleotide structure

  pentose sugar

  phosphate group

  organic base
• structure of atp

  adenosine triosphate

  adenine organic base

  pentose sugar

  these two form adenosine
• DNA nucleotide

  deoxyribonucleic acid

  holds genetic information

  contains:

  phosphate group

  organic base

  deoxyribose sugar
• structure of dna

  double stranded that twists into a helix

  two sugar phosphate backbones

  held by hydrogen bonds between complimentary organic bases

  the strands are anti-parallel
• rna nucleotide

  ribose sugar

  phosphate group

  organic base

  short and single stranded
• the two types of bonds in dna

  hydrogen -> between complimentary bases on opposite strands of dna

  phosphodiester -> between phosphate groups of bases on the same strand of dna
• hydrolysis and condensation reactions of dna

  condensation -> forms a polynucleotide as a phosphodiester bond forms between two bases

  hydrolysis -> breaks the phosphodiester bond between two nucleotides
• semi-conservative replication

  1. dna helicase unwinds the double helix by breaking the hydrogen bonds between complimentary bases
  2. dna polymerase binds free complimentary nucleotides to both originally dna strands via complimentary base pairing
  3. daughter dna molecules rewind into a double helix
• protein synthesis - transcription

  1. dna helicase unzips the dna helix by breaking the hydrogen bonds between complimentary bases
  2. rna polymerase attaches free nucleotides via complimentary base pairing
  3. this continues until a stop codon is reached
• protein synthesis - translation

  1. mrna moves from the nucleus through a nuclear pore to the cytoplasm
  2. it attaches to a ribosome
  3. trna with a complimentary anticodon carrying a specific amino acid moves to the ribosome and pairs with the first mrna codon
  4. the ribosome moves along the mrna to the next codon and pairs up with a complimentary trna to repeat the process above
  5. energy released from atp is used to form a peptide bond between the two amino acids
  6. when a third trna binds, the ribosome releases the first trna
  7. a stop codon is reached and the process stops
• calculate the proportion of A, C, and G nucleotides if the proportion of T is 42%

  as A is a complimentary base of T then it also must be 42 %

  the total four bases add up to 100 %

  so T + A = 84 %

  100 - 84 = 16 %

  so therefore C + G = 16 %

  and are each worth 8 % ( as 16 divided by 2 is 8 )
• N14 and N15 experiment analysis

  in the parent generation the entire dna molecule is high density in the first generation, the N15 dna replicates into two daughter helixes each with intermediate density as one strand is made up of N14 and one of N15 in the second generation, the two dna helixes replicate again to form two helixes that are N15 and N14, and two helixes that are fully N14 and N14

  -> this shows how dna replication is semi-conservative
• how is ATP made in cells

  substrate level phosphorylation

  condensation reaction between ADP and Pi

  using energy release when a high energy level substrate is broken down into lower energy level products
• what needs to be transported into the nucleus for dna replication

  free nucleotides

  dna polymerase

  primers
• how many hydrogen bonds does C and G form

  3
• how many hydrogen bonds do A and T form

  2
• which are pyrimidines

  C and T
• which are purines

  A and G
• which stain would be chosen to bind to the phosphate group of DNA to make chromosomes more visible when using a light microscope

  methylene blue - positively charged
• pyrimidine rings

  1
• purine rings

  2
• role of dna ligase

  as dna polymerase only works in the 3 to 5 direction

  this means the lagging strand has small gaps left in the backbone

  so dna ligase seals these gaps by forming phosphodiester bonds
• how are the two dna strands held together

  phosphodiester bonds between two consecutive nucleotides in the sugar-phosphate backbone

  hydrogen bonds form between two complimentary nitrogenous bases in the two dna strands

  3 between C and G

  2 between T and A
• similarities between atp and dna nucleotide structure

  pentose sugar

  adenine base

  phosphodiester bond

  phosphate group
• difference between atp and dna nucleotide structure

  atp:

  two additional phosphates

  deoxyribose replaced by ribose
• how do pairing of nitrogenous bases allows identical copies of DNA to be made

  adenine binds with thymine

  cytosine binds with guanine

  by hydrogen bonding

  purines can only bind with pyrimidines
• one Kb of double stranded DNA has a length of 0.34 μm

  the DNA in the nucleus of a cell from a fruit fly is 5.6 cm

  calculate the number of Kb in the DNA of the fruit fly

  5.6 / 0.34 = 16.47058

  16.47058 x 10,000 to get from μm to cm

  = 164,706
• differences between dna replication and transcription

  transcription:

  only a small section of dna is unzipped

  only one strand acts as a template strand

  free rna nucleotides instead of dna nucleotides

  rna polymerase instead of dna polymerase

  the mrna leaves the nucleus where as the new dna strands do not
• semi-conservative

  new dna is comprised of one parent strand and one new strand

  each strand acts as a template
• what does gyrase do

  uncoils the dna
• why is transcription necessary for polypeptide synthesis

  dna transcribed to rna

  which is smaller than dna allowing it to leave the nucleus

  to be translated at the ribosomes