water

• most abundant molecule in cell = WATER
• WATER = 70% or more total cell mass
• POLAR = polarity of water that enables water molecules to form hydrogen bonds with each other or with other polar molecules and interact with positively or negatively charged ions
• HYDROPHILIC = ions and polar molecules are readily soluble in water
• HYDROPHOBIC = non-polar ; cannot interact with water, are poorly soluble in an aqueous environment
• WATER = acts as a solvent for many chemical reactions and also helps transport dissolved compounds into and out of cells
• WATER = a metabolite in many chemical reactions like photosynthesis, digestion, and aerobic respiration.
• WATER = a reactant or product in many metabolic reactions as an excellent nucleophile
• WATER BALANCE

  • hypothalamic mechanisms that control thirst
  • antidiuretic hormone (ADH)
  • retention or excretion of water by the kidneys, and on evaporative loss
• NEPHROGENIC DIABETES INSIPIDUS = lack of ADH

  • the inability to concentrate urine or adjust to subtle changes in extracellular fluid osmolarity, results from the unresponsiveness of renal tubular osmoreceptors to ADH. 
• PROPERTY OF WATER = POLARITY

  • OXYGEN = slight negative charge [ - ]
  • HYDROGEN = slight positive charge [ + ]
• Di-pole = An oxygen atom has a much stronger attraction for electrons than a hydrogen atom with its single proton.
• MOLECULAR INTERACTIONS = hydrogen bonding & di-pole interactions
• H BONDING = the force of attraction between a hydrogen molecule with a partial positive charge and another atom or molecule with a partial or full negative charge
• Hydrogen bonds are NOT as strong as covalent or ionic bonds, and they can form in other compounds besides water.
• Water is able to form MULTIPLE HYDROGEN BONDS that accounts for many of its special properties.
• PROPERTY OF WATER = COHESION, ADHESION, SURFACE TENSION

  • COHESION holds water together
  • ADHESION holds water molecules to other polar substances
  • SURFACE TENSION is caused by cohesion of water to itself and lack of adhesion to air
• PROPERTY OF WATER = HIGH SPECIFIC HEAT OF WATER

  • Water has an extremely HIGH SPECIFIC HEAT (amount of energy needed to raise the temperature)
  • Energy is stored in hydrogen bonds and molecular motion
  • Water moderates' temperature
• PROPERTY OF WATER = HEAT VS TEMPERATURE

  • HEAT is the total kinetic energy in an object ; related to mass
  • TEMPERATURE is the average kinetic energy ; mass doesn't matter
• PROPERTY OF WATER = SOLUBILITY / UNIVERSAL SOLVENT

  • Water dissolves a huge range of compounds (universal solvent) due to its molecular interactions.
  • SOLUTION = evenly distributed mixture of 2 or more substances
  • SOLVENT = Dissolving substance (usually water)
  • SOLUTE = dissolved substance
• TYPES OF SOLUTE

  • HYDROPHOBIC substance DO NOT FORM Hydrogen bonds with water
  • HYDROPHILIC substances form Hydrogen bonds with water ( ions,sugars, cellulose, some proteins )
• HOMOGENOUS = HYDROPHILIC
• HETEROGENOUS = HYDROPHOBIC
• CHEMICAL REACTION = OXIDATION

  • INCREASE in oxidation number
  • ADDITION of oxygen
  • REMOVAL of hydrogen
• CHEMICAL REACTION = REDUCTION

  • DECREASE in oxidation number
  • ADDITION of hydrogen
  • REMOVAL of oxygen
• CHEMICAL REACTION = HYDROLYSIS

  • reaction in the presence of water, acid, base or enzyme
• .CHEMICAL REACTION = TAUTOMERISM

  • interconversion of aldehyde/ketone to alcohol
• CHEMICAL REACTION = CONDENSATION

  • reaction of two or more substances with the removal of water from the molecules.
• DISSOCIATION OF WATER

  • From the reaction of two water molecules, the following equilibrium constant expression can be written:
  • K = [H3O+][OH-] / [H2O]^2
  • Multiplying both sides by [H2O]2 yields Kw
  • Kw = [H3O+][OH-] ; Kw = ion-product constant
• HIGH SURFACE TENSION

  • the ability of water molecules to shrink into the minimum surface area possible
  • SURFACE TENSION = allows insects to float and slide in a water surface
• DENSITY OF WATER

  • dependent on temperature
  • density of liquid water - 1.0 g/mL or 1.0 g/cc
  • density of ice - less than 1.0 g/mL
  • ice floats in water = important in aquamarine lives
• BOILING POINT = 100 degrees Celsius
• MELTING POINT = 0 degrees Celsius
• SPECIFIC GRAVITY = 1 ; equal to density of water