Water

 It is a main component of all organisms and provides a medium for metabolic reactions to occur  Three properties that make it unique:  Cohesive  Solvent  Thermal

Cohesion  Attraction between molecules of the same substance  Water molecules attract each other because of H bonds Hydrogen bonding between water molecules

Cohesion  Surface tension  Forms droplets

Adhesion  Attraction between molecules of different types  Water sticks to other materials  “Capillary action”

Expands When it Freezes  Ice is less dense than liquid water

Expands When it Freezes  Helps living things because:  Ice floats on lakes, ponds, etc.  Colder water sinks “turnover”  Arctic waters are insulated  Water freezes inside the cracks of rocks causing them to break apart (forms soil)

Water is a good solvent  “Universal solvent”  Acts as a medium for most biochemistry in the cell  Fluids in the body are mostly H 2 O  Cytoplasm, blood, stroma

Solvent Properties  Water also acts as a transport medium for nutrients within organisms  Xylem and phloem in plants  Blood in animals carries glucose, amino acids, fibrinogen (clotting) etc.

Resist Temperature Change  Water has a high specific heat and heat of vaporization  Water requires a lot of heat to increase its temperature  Cools slowly too

Resist Temperature Change  Acts as an insulator for cells  Keeps aquatic environments thermally stable  Sweating/ transpiration allow for rapid cool

Other properties  Colorless, allows for a lot of light to pass through tissue and lakes, oceans, etc.