Unit 1 Biomolecules [Water and Inorganic ions]

• What is the major component of cells?

  Water
• What results from the polar nature of water?

  Water has unusual properties
• What type of molecule is water?

  Dipolar molecule
• What does a water molecule consist of?

  Two hydrogen atoms and one oxygen atom
• Why are the electrons in a water molecule not shared equally?

  The oxygen atom has a greater electronegativity
• What charge does the oxygen atom in a water molecule have?

  Partial negative charge
• What charge do the hydrogen atoms in a water molecule have?

  Partially positive charge
• What is a hydrogen bond?

  An attractive force between opposite charges
• Why are hydrogen bonds significant in water?

  They are responsible for many unique properties of water
• At what temperature is water most dense?

  4°C
• What happens to water when it freezes?

  It expands and becomes less dense than liquid water
• Why does ice float on water?

  Because ice is less dense than liquid water
• How does ice benefit aquatic environments?

  It forms an insulating layer that prevents the water below from freezing
• What role does water play in metabolic reactions?


  It is the medium in which enzyme-catalyzed reactions take place
• What is hydrolysis?


  A reaction that breaks down complex molecules using water
• What is one of the raw materials required in photosynthesis?

  Water
• Why is water called the universal solvent?

  Because it dissolves more substances than any other liquid
• What happens to ionic compounds when they dissolve in water?

  The ions separate and are surrounded by water molecules
• What are some examples of substances that water readily dissolves?

  Respiratory gases, excretory products, inorganic ions, and small hydrophilic molecules
• What is cohesion in relation to water molecules?

  The attraction between molecules of the same type
• What is adhesion in relation to water molecules?

  The attraction of molecules of one kind for molecules of a different kind
• What causes surface tension in water?

  The unequal distribution of hydrogen bonds at the surface
• Why is surface tension important for some organisms?

  It allows some insects to stay afloat on the surface of water
• What is specific heat capacity?

  The amount of heat energy required to raise the temperature of a substance by 1°C
• Why does water have thermal stability?

  Because of its high specific heat capacity
• What is the specific heat capacity of water?

  1. 186 J/g°C
• How much energy is required to raise the temperature of 3 kg of water from 10°C to 15°C?

  $62850 \text{ J}$
• What is latent heat of vaporization?

  The energy required for a substance to change from liquid to gas
• Why is sweating an effective means of cooling the body?

  Because the evaporation of sweat removes heat energy from the body
• What is an ion?


  An atom that has an electric charge due to losing or gaining electrons
• What role do common ions play in organisms?

  Each type of ion has a specific role depending on its properties
• What are the key properties of water that make it essential for life?

  • Water as a metabolite in condensation, hydrolysis, photosynthesis, and respiration
  • Water as a solvent for metabolic reactions
  • High specific heat capacity resists temperature changes
  • High latent heat of vaporization provides a cooling effect
  • Cohesion supports columns of water in plant xylems
  • Surface tension supports small organisms
  • Ice floats, maintaining aquatic habitats
  • Water is transparent, allowing light for photosynthesis
• What property of water contributes to its thermal stability?

  High specific heat capacity
• What is specific heat capacity?

  It is the amount of heat energy required to raise the temperature of a substance by a specific unit of mass.
• How much energy is required to raise the temperature of 1 kg of water by 1°C?

  1. 186 Joules
• Why does water have a high specific heat capacity?

  Because water molecules are bonded together by many hydrogen bonds that require a lot of energy to break.
• What effect does water's high specific heat capacity have on temperature variation in organisms?

  It results in little variation in temperature within organisms' bodies or in the surrounding water.
• How does the high specific heat capacity of water benefit aquatic environments?

  It allows the aquatic environment to be temperature stable, buffering organisms against sudden temperature changes.
• What is the equation relating heat energy to specific heat capacity?

  E = mcΔT
• If you wanted to find out how much energy is required to raise the temperature of 5 kg of pure water from 10°C to 15°C, what would be the calculation?


  E = 5 \times 4.186 \times 5 = 104.65 \text{ kJ} \approx 62850 \text{ J}