Water and Nucleic Acids

Water

    Cohesion

  • Cohesion → attraction between water molecules
  • Cohesion occurs because of hydrogen bonding
  • More hydrogen bonds → stronger cohesive forces

    Xylem

  • Cohesion allows for the continuous movement of water in the xylem
  • Attractive forces of water in the leaves are stronger than attractive forces of water in the roots (negative pressure created due to cellular respiration)
  • Columns in xylem can be maintained because there is typically not enough energy in external forces (that is naturally available) to break the cohesive forces

    Surface Tension

  • Cohesion is responsible for surface tension
  • Surface tension shrinks to form the minimum possible area
  • Surface tension allows objects to float on surfaces, which creates habitats (mosquito larvae hang on the surface of water and live underneath the surface)

    Adhesion

  • Adhesion → attraction between water and a solid composed of polar molecules
  • Example: if there is an air-filled section of the xylem, adhesion will allow water to ascend and fill the gap

Solubility in Water

    Hydrophilic Substances

  • Are attracted to water’s poles
  • Are polar
  • Dissolve because they become surrounded by water’s poles
  • Example: salt and sugar

    Hydrophobic Substances

  • Are not attracted to water’s poles
  • Are usually non-polar
  • Are more attracted to other non-dissolving-in-water substances
  • Can sometimes dissolve in non-polar solutions
  • Example: fats, oils, and all lipids

    Role of Solubility in Life

  • Substances can be transported as aqueous solutions
  • Example: mineral ions transported in a xylem sap
  • Example: glucose transported in plasma due to its solubility

Viscosity

  • How easily a fluid can flow
    • Example: maple syrup has a higher viscosity than water
  • Viscosity is caused by internal friction
  • Solutes increase viscosity
    • Example: saltwater is more viscous than freshwater
  • Gasses are always less viscous than liquids

Thermal Conductivity

  • Water is thermally conductive
  • Fat, oils, and air are much less conductive than water
    • Therefore, it is easier for animals in air to maintain body heat than in water

Specific Heat

  • Specific heat → the amount of energy required to raise the temperature of 1g of material by 1°C or 1K (Kelvin)
  • Water has a high specific heat because it takes lots of energy to break the hydrogen bonds within water
  • Air has a much lower specific heat than water
    • This is why aquatic habitats are much more thermally stable than terrestrial habitats

Nucleic Acids

    Nitrogenous Bases

  • C - Cytosine
  • G - Guanine
  • T - Thymine
  • A - Adenine
  • U - Uracil
  • Adenine and Guanine are double-ringed purines
  • Thymine, Cytosine, and Uracil are all single-ringed purines
  • A makes 2 hydrogen bonds with T/U
  • G makes 3 hydrogen bonds with C
  • Mismatched pairing would destabilize DNA

    DNA (Deoxyribonucleic Acid)

  • Has nitrogenous bases (A,T,C,G)
  • Consists of hydrogen connected to 2 carbon (deoxi-)
  • It is double stranded
  • DNA is the genetic material of all living things
  • It contains instructions to live, develop, survive, and reproduce
    • DNA is the master/original copy of genetic instructions
  • Made up of monomers (nucleotides)

    RNA (Ribonucleic Acid)

  • Has nitrogenous bases (A,U,C,G)
  • Consists of hydroxide connected to 2 carbon
  • It is single stranded
  • It is a temporary replica of DNA
  • Made up of monomers (nucleotides)