properties of water all organisms require h 2 o. background nh2onh2o n life evolved in the early...
TRANSCRIPT
Properties of Water
All organisms require H2O
Background
H2O Life evolved in the early oceans Vital to history of life on Earth
3/4’s of Earth is covered with H2O
Human’s are 2/3’s H2O
Polarity of H2O
O
HH+ +
-
108°
Oxygen is very electronegative.
i.e. It likes e-s.
Polarity of H2O (cont.)
e-s are shared unequally b/t H’s & O’s
H2O molecules are polar!
Hydrogen Bonding
Weak chemical associations w/ other molecules, like little magnets sticking together
Accounts for much of the organization of living chemistry
A lot of bonds work together for strength
Generally indicated by dashed lines
Do the water molecule shuffle!
The structure of water leads to some interesting properties of water……
Water is the Universal Solvent
Like dissolves like
Anything with a charge or polar will dissolve in water
Anything nonpolar will not dissolve in water
– eg. NaCl + H20
Na+ Cl-
OO
H
H
HH
+
Some examples:
Hard water Caves Salty ocean Hydrophobic vs. Hydrophilic molecules
Hydrophobic & Hydrophilic Interactions
Very important in biological systems
– ex. Cell membranes
Cell Membrane
Cohesion and Adhesion
Water molecules stick to one another Examples:
Surface tension Water molecules stick to other charged
substancesExamples:
MeniscusCapillary Action
Boating Spiders
Water Walking Spiders
Water has a high specific heat
1kcal/1goC Absorbs a lot of heat to raise T Must break H bonds to pull the
molecules apart
A comparison…. (No need to copy this in your notes!)
2 X oil or alcohol 4 X air or Al 9 X iron Only ammonia is greater
“So what,” you may be asking?
Temperature regulation- large thermal capacity
Oceans
Body Temperature
Thermal Conductivity-disperses heat evenly throughout a body
Water has a high boiling point
Liquid Gas + 540 cal.
Evaporation is a cooling process
Freezing Point of water is high
Water is less dense as a solid than a liquid (that is really weird!)
Solid water floats on its liquid form So, what does this mean to aquatic life?
To summarize---
Life is dependent on water
Life Evolved in water
50-90% of wt. Of any living thing is water
70% human is water Blood plasma cytoplasm
Medium of transport
Molecules/nutrients Wastes Sex Cells Development of fetus
Temperature Regulation
Sweat Blood
Buoyance
Movement Predation/Prey
Waterproofing
Integument