Nucleic Acids

• DNA


  Carries genetic information
• RNA


  Transfers genetic information from DNA to ribosomes
• Nucleotides


  Consist of pentose (5 carbon sugar), a nitrogen containing organic base, and a phosphate group

  
• Components of a DNA nucleotide

  • Deoxyribose
  • Phosphate group
  • Adenine, cytosine, guanine or thymine

  
• Components of an RNA nucleotide


  • Ribose
  • Phosphate group
  • Adenine, cytosine, guanine or uracil

  
• Nucleotides joining together


  By phosphodiester bonds formed in condensation reactions

  
• DNA molecule


  Double helix composed of two polynucleotides joined by hydrogen bonds between complementary bases
• RNA


  Relatively short single polynucleotide chain
• ATP


  Nucleotide derivative consisting of ribose, adenine and three phosphate groups

  
• ATP hydrolysis


  Releases energy to form ADP and a phosphate molecule, catalysed by ATP hydrolase
• Inorganic phosphate


  Can be used to phosphorylate other compounds, making them more reactive
• ATP synthesis


  Condensation of ADP and inorganic phosphate catalysed by ATP synthase, produces ATP during photosynthesis and respiration
• DNA replication


  Semi-conservative replication ensures genetic continuity between generations of cells
• Steps of semi-conservative DNA replication

  1. DNA helicase unwinds double helix and separates strands

  2. Complementary base pairing occurs between template strands and free nucleotides

  3. DNA polymerase joins adjacent nucleotides by phosphodiester bonds

  
• Genetic code


  Order of bases on DNA, triplets of bases code for particular amino acids (codons)

  
• Genetic code


  • Non-overlapping, degenerate (more than one triplet codes for same amino acid), contains start and stop codons
• Transcription


  DNA strand transcribed into mRNA in the nucleus by RNA polymerase
• Translation


  Amino acids assembled into polypeptide chain, involving mRNA, tRNA and ribosomes
• Not all the genome codes for proteins - non-coding sections are called introns, coding regions are called exons