water

  • Basic structure of male & female hormones is identical

    • identical carbon skeleton 

    • attachment of different functional groups

    • interact with different targets in the body

      • different effects

A water molecule (H2O), is made up of three atoms --- 

  • one oxygen and 

  • two hydrogen.


Polar

  1. the oxygen atom attracts more than its "fair share" of electrons

  2. The oxygen end “acts” negative

  • The hydrogen end “acts” positive

  • Causes the water to be POLAR (think poles of a magnet!)


Interaction Between Water Molecules

  • Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule to form a HYDROGEN BOND (Pic 1 pic below and draw on your paper)

Properties of Water

  1. Cohesion & adhesion

    1. ex-(Surface tension, capillary actions)

  2. Lower density as a solid

    1. Ex- (ice floats over liquid water)

  3. High specific heat 

    1. Water stores heat 

  4. High heat of vaporization

    1.  Alot of energy needed to change states

  5. Good Solvent

    1. Hydrophilic vs hydrophobic

Coheisn

  • Attraction between particles of the same substance 

    • (why water is attracted to itself)

      • Results in Surface tension (a measure of the strength of water’s surface)

      • Produces a surface film on water that allows insects to walk on the surface of water


Adhesion

  • Attraction between two different substances.

    • Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton. 

    • Capillary action-water molecules will “tow” each other along when in a thin glass tube.

      • Example: transpiration process which plants and trees remove water from the soil, and paper towels soak up water.

      • Adhesion Causes Capillary Action

Water is Less Dense as a Solid

  • Ice is less dense as a solid than as a liquid (ice floats)

  • Liquid water has hydrogen bonds that are constantly being broken and reformed.

  • Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances.

  • D=m/v



High Specific Heat

  • Amount of heat needed to raise or lower 1g of a substance 1° C.

  • Water resists temperature change, both for heating and cooling.

  • Water can absorb or release large amounts of heat energy with little change in actual temperature.

    • H2O moderates temperatures on Earth


High Heat of Vaporizatio

  • Amount of energy to convert 1g of a substance from a liquid to a gas

  • HYDROGEN BONDS: Water molecules are held together by a strong  network of hydrogen bonds

  • Energy Input: In order for water to evaporate, hydrogen bonds must be broken requiring a substantial amount of energy

  • As water evaporates, it removes a lot of heat with it.

water vappor

  • Water vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm.

  • Heat radiated from the sun warmed surface of the earth is 

  absorbed and held 

  by the vapor.

Homeostasis

  • Ability to maintain a steady state despite changing conditions

  • Water is important to this process because:

a.  Makes a good insulator

b.  Resists temperature change

c.  Universal solvent

d.  Coolant

e.  Ice protects against temperature  extremes (insulates frozen lakes)


Water is the universal solvent

  • POLARITY ALLOWS WATER TO DISSOLVE ANYTHING WITH A CHARGE!

  • Water is usually part of a mixture.

  • There are three types of mixtures:

    • Solutions

    • Colloids 

    • Suspensions


Solution

  • Ionic compounds disperse as ions in water

  • Evenly distributed

  • SOLUTE (Na+Cl-)

    • Substance that is being dissolved

  • SOLVENT (H2O)

    • Substance into which the solute dissolves


Acids, Bases and pH

  • One water molecule in 550 million naturally dissociates into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-)

The pH Scale

  • Indicates the concentration of H+ ions

  • Ranges from 0 – 14

  • pH of 7 is neutral

  • pH 0 up to 7 is acid … H+

  • pH above 7 – 14 is basic… OH-

  • Each pH unit represents a factor of 10X change in concentration

  • pH 3 is 10 x 10 x 10 (1000) stronger than a pH of 6

Buffers

  • Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH (neutralization).

  • Produced naturally by the body to maintain homeostasis


The degree of acidity or alkalinity (basic) is important in organisms.  The body must constantly maintain a near neutral pH (7) in the blood and body tissues.  To do this, the body produces buffers that can neutralize acids.  Acidic and basic conditions in the body occur due to different metabolic reactions taking place throughout the body.  

The force of attraction between molecules is so strong that the oxygen atom of one molecule can actually remove the hydrogen from other water molecules.  This reaction is known as dissociation, and it takes place in our cells.  Water (H20) dissociates into H+ and OH- ions.  The OH- ion is called the hydroxide ion, while the H+ ion is called the hydrogen ion.  Free H+ ions can react with another water molecule to form the H3O+ or hydronium ion.

Acidity or alkalinity is a measure of the relative amount of H+ and OH- ions dissolved in a solution.  Neutral solutions have an equal number of H+ and OH- ions.  Acids have more H3O+ ions than OH- ions.  Acids taste sour and can be corrosive.  Digestive fluids in the body are acidic and must be neutralized by buffers.  Bases contain more OH- ions than H3O+ ions.  Bases taste bitter and feel slippery.

When an acid is combined with a base, neutralization occurs.  The result of neutralization is a salt and water.  Neutralization helps return our body pH to neutral.  The process of our bodies maintaining neutral pH so that proteins can work properly without being denatured (unfolded) is known as homeostasis.