Nucleic Acids, ATP, and Water

Nucleic Acids, ATP, and Water

1. DNA and RNA are polymers of Nucleotides

   • DNA
     • The pentose sugar in DNA nucleotide is deoxyribose
       • Each have the same sugar and phosphate group
         • Bases can differ
           • A , T, C, G
     • Used to store genetic information
   • RNA
     • Similar structure to DNA
     • Used to transfer genetic information from the DNA to the ribosomes
     • RNA contains Ribose sugar
       • also contains phosphate group
         • and bases, A, C, U, G
   • Type of biological molecule
     • Containing pentose sugar, organic base, phosphate group
   • Nucleotides joined together to form polynucleotides
     • joined via condensation reactions
       • Forming a phosphodiester bond between phosphate group and a sugar of another nucleotide
         • Chain of sugar, phosphate called sugar-phosphate backbone

2. DNA is made of two polynucleotides in a double-helix structure

   • DNA polynucleotides joined by hydrogen bonding between bases
     • Bases only join to one to another - complementary base pairing
       • A -- T
         • Equal base pairs in a molecule
       • C --- G
       • The two polynucleotides run antiparallel and twist to form helix
   • RNA is a relatively short polynucleotide chain
     • Made from single chain

3. DNA Replication

   • Replicates by Semi-Conserative replication
     • Half of the strands, in each new DNA molecule, are from the original DNA
       • Maintains genetic continuity between cell generations
     • Enzyme DNA helicase breaks hydrogen bonds between complementary base pairs
       • Makes the DNA helix unwind to form two single strands
         • These two new strands act as a template for a new strand.
           • Complementary base pairing means that free DNA nucleotides are attracted to the exposed bases
             • Condensation reactions join the new strands together
               • Catalysed by DNA Polymerase
                 • Moves in opposite ways along antiparallel DNA strand
                   • Each end of DNA molecule is different
                     • 3' and 5' run antiparallel - run side by side but in opposite directions
                       • Active site of DNA polymerase complementary to original 3' end
                         • New nucleotides only start on the 3' end of the orignal strand
                           • Meaning if antiparallel forms the 5' end of new strand at the 3' end of the orginal strand
                             • New strand made in the 5' to 3' direction
                               • DNA polymerase starts at the 3' end and moves 3' to 5' direction on the original strand
                                 • Two DNA polymerases working on one orginal DNA double-helix move in opposite directions to each other
               • Hydrogen bonds reform between the original and new bases
                 • Each new DNA molecule contains a original strand and a new strand

4. Unique Properties of Water

   • Functions or water to living organisms
     • Metabolic processes
       • E.g. condensation / hydrolysis reactions
       • Water is a metabolite
     • Used as a solvent
       • Substances can dissolve in it
         • Most reactions take place in solution - cytoplasm
     • Temperature Control
       • Takes a lot of energy to evaporate water - breaking hydrogen bonds between water
         • Used to cool down organisms without losing too much water
       • High specific heat capacity
         • Resists rapid temperature changes
     • Cohesive
       • Stick together - helpful in water transportation in plants
         • Cohesion - attaction between molecules of the same type
   • Structure of Water
     • Polar molecule, partially negative oxygen and 2 partially positive hydrogens
       • Charged ions in water will be completely surronded by water (dissolved)
         • Positive ions will attract negative oxygen
         • Negative ions attract positive hydrogen
         • Water requires special channel proteins to move through membranes
           • Aquaporins allow polar water to diffuse

5. ATP

   • Cells get energy from glucose in respiration
     • Energy can't be used directly from glucose
       • Use energy to form ATP
         • ATP used to release energy
   • Made from the nuleotide base adenine
     • ribose sugar and 3 phosphate
       • Energy stored in bonds between the phosphate groups
         • Hydrolysis reaction
           • phosphate bond broken
             • A lot of energy released
               • ATP can be resynthesised using products in condensation reaction
   • Immediate source of energy
     • ATP can diffuse to parts of the cell that need energy

Images and files in the map