1.5 - Nucleic acids

• DNA


  Carries genetic information
• RNA


  Transfers genetic information from DNA to ribosomes
• Nucleotides


  Polymers that DNA and RNA are made of, consisting of a pentose sugar, a nitrogen-containing organic base, and a phosphate group

  
• Components of a DNA nucleotide

  • Deoxyribose
  • Phosphate group
  • Adenine
  • Cytosine
  • Guanine
  • Thymine

  
• Components of an RNA nucleotide


  • Ribose
  • Phosphate group
  • Adenine
  • Cytosine
  • Guanine
  • Uracil

  
• Phosphodiester bonds


  Bonds that join nucleotides together
• DNA molecule


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


  Relatively short polynucleotide chain
• Amino acids


  Monomers that proteins are made of, containing an amino group, carboxylic acid group, and a variable R group
• There are 20 different amino acids with different R groups
• Peptide bonds


  Bonds that join amino acids together
• Dipeptide


  Contains two amino acids
• Polypeptide


  Contains three or more amino acids
• Primary structure of a protein

  • Order and number of amino acids
• Secondary structure of a protein


  • Shape of the amino acid chain, either alpha helix or beta pleated sheet, determined by bonding
• Tertiary structure of a protein

  • 3D shape, can be globular or fibrous
• Fibrous protein


  • Collagen
• Collagen


  • Strong due to hydrogen and covalent bonds, forms structure of bones, cartilage, connective tissue, and tendons
• Globular protein

  • Haemoglobin
• Haemoglobin


  • Water soluble, consists of two beta polypeptide chains and a haem group, carries oxygen in the blood

  
• Protein synthesis


  1. Transcription (in nucleus, DNA to mRNA)

  2. Translation (in cytoplasm, mRNA to polypeptide chain)
• Transcription


  DNA uncoils, one DNA strand used as template, free nucleotides line up by complementary base pairing, phosphodiester bonds form mRNA, mRNA moves to cytoplasm
• Translation


  mRNA attaches to ribosome, tRNA collects amino acids and carries them to ribosome, amino acids join by peptide bonds, process repeats until stop codon reached
• Semi-conservative replication of DNA


  Ensures genetic continuity between generations of cells
• Semi-conservative replication of DNA


  Double helix unwinds, hydrogen bonds break, one strand used as template, complementary base pairing, phosphodiester bonds formed by DNA polymerase
• ATP


  Nucleotide derivative consisting of ribose, adenine, and three phosphate groups

  
• ATP hydrolysis


  Energy released, catalysed by ATP hydrolase, inorganic phosphate can phosphorylate other compounds
• ATP synthesis


  Condensation of ADP and inorganic phosphate, catalysed by ATP synthase, occurs during photosynthesis and respiration