Chapter 3 Chapter 3 Water and the Fitness of the Water and the Fitness of the

EnvironmentEnvironment

1.1. Why is water special?Why is water special?

2.2. Unique Properties of WaterUnique Properties of Water

3.3. Acidic/Basic conditionsAcidic/Basic conditions

Abundance of water is the main reason the Abundance of water is the main reason the Earth is habitableEarth is habitable

Earth’s surface – 75% submerged in waterEarth’s surface – 75% submerged in water

Why is water special?Why is water special?

Molecule that supports all lifeMolecule that supports all lifeBiological MediumBiological MediumMetabolic ReactionsMetabolic Reactions

Required for survival of all living Required for survival of all living organismsorganisms

Exists in nature in all 3 statesExists in nature in all 3 states

Water StructureWater Structure

Polar moleculePolar molecule

DipoleDipole

H bondsH bonds

Contributes to Contributes to

unique propertiesunique properties

What’s wrong with this picture?What’s wrong with this picture?

Unique Properties of WaterUnique Properties of Water

1.1. Ice floatsIce floats

a. Less dense a. Less dense

than liquid than liquid

waterwater

b. H bonds more b. H bonds more ordered and stable in ordered and stable in solid watersolid water

Since Ice floats in waterSince Ice floats in water

Life can existLife can exist

under the frozen under the frozen surfaces of lakessurfaces of lakes

and polar seasand polar seas

Unique Properties of WaterUnique Properties of Water

2.2. Water has high specific heatWater has high specific heata.a. Moderates air tempModerates air temp

1. When air is warmer 1. When air is warmer

2. When air is cooler2. When air is cooler

Review termsReview terms

1. Kinetic energy1. Kinetic energy

2. Heat2. Heat

3. Temperature3. Temperature

Review termsReview terms

4. specific heat of a substance4. specific heat of a substance

Unique Properties of WaterUnique Properties of Water

2.2. Water’s high specific heatWater’s high specific heat

a. Resists changea. Resists change

b. Large bodies of water can absorb heat w/o b. Large bodies of water can absorb heat w/o large temp changelarge temp change

c. Heat absorbed when H bonds breakc. Heat absorbed when H bonds break Heat released when H bonds formHeat released when H bonds form

d. Bio sigd. Bio sig1.1. Water keeps temp fluctuations to within Water keeps temp fluctuations to within

limits that permit lifelimits that permit life

2.2. Due to H bonding, water molecules hold Due to H bonding, water molecules hold tightly to each othertightly to each other

3.3. Aids in homeostasis Aids in homeostasis

Unique Properties of WaterUnique Properties of Water

3.3. High heat of vaporizationHigh heat of vaporization

a. Vaporization (evaporation)a. Vaporization (evaporation)

b. Heat of vaporizationb. Heat of vaporization

c.c. Bio sigBio sigEvaporative CoolingEvaporative Cooling Due to high heat of vaporizationDue to high heat of vaporization Allows water to cool a surfaceAllows water to cool a surface

ex. ex.

Unique Properties of WaterUnique Properties of Water

4.4. CohesionCohesiona.a. As a liquid, water forms FRAGILE H bondsAs a liquid, water forms FRAGILE H bonds

b.b. H bonds are constantly breaking and H bonds are constantly breaking and reformingreforming

c.c. Definition of cohesionDefinition of cohesion

d.d. Bio sigBio sig

Transport of Transport of water and water and dissolved dissolved nutrients nutrients against against gravitygravity

Pond WalkersPond Walkers

e.e. Bio sigBio sig

1. Surface Tension1. Surface Tension

2. Skin of tightly H 2. Skin of tightly H bonded water bonded water molecules, forms molecules, forms @air/water interface@air/water interface

Unique Properties of LifeUnique Properties of Life

5.5. The Solvent of LifeThe Solvent of Lifea. Termsa. Terms

1. Solution1. Solution

2. Solvent2. Solvent

3. Solute3. Solute

4. Aqueous Solution4. Aqueous Solution

b.b. Water is versatile solventWater is versatile solvent1.1. HydrophilicHydrophilic

2.2. HydrophobicHydrophobic

c.c. Why?Why?

PolarityPolarity

Two impt featuresTwo impt features

1. shape1. shape

2. H bonds2. H bonds

d.d. Water has ability to dissolve macromoleculesWater has ability to dissolve macromoleculese.e. Can form sphere of hydrationCan form sphere of hydration

ex. Fig 3-7 Lysozyme molecule ex. Fig 3-7 Lysozyme molecule

f.f. Hydration shellHydration shell

Polar water can Polar water can interact with ionic interact with ionic compounds compounds

called called solutessolutes and and

dissolve themdissolve them

g.g. Most biochem rxns occur in waterMost biochem rxns occur in water

To calculate concentration of solutes in To calculate concentration of solutes in aqueous solutions:aqueous solutions:

1. Mole1. Mole

2. Molarity2. Molarity

Unique Properties of WaterUnique Properties of Water

6.6. Water and pHWater and pH

a. Dissociation of water molecules affect a. Dissociation of water molecules affect living organismsliving organisms

b.b. Acid/BaseAcid/Base

1. Acid1. Acid

2. Base2. Base

c.c. pHpH

1. determined by relative conc of H1. determined by relative conc of H++ ionsions

2. Definition2. Definition

pH = pH =

d.d. pH scalepH scale

1. acidic1. acidic

2. basic2. basic

e.e. Bio sigBio sig

1. Homeostasis1. Homeostasis

all living orgs have a vary narrow all living orgs have a vary narrow pH pH range over which they can survive.range over which they can survive.

2. Organisms maintain pH by using2. Organisms maintain pH by using

f.f. BuffersBuffers

a. Substances that minimize changes in a. Substances that minimize changes in the concentrations of Hthe concentrations of H++ and OH and OH-- ions in ions in a solutiona solution

b. Buffer systems are reversible – b. Buffer systems are reversible – depends of Hdepends of H++ concentration concentration

Buffers consist of:Buffers consist of:

Weak acid and its anionic saltWeak acid and its anionic salt

1.1. Weak acid dissociates in aq. SolutionWeak acid dissociates in aq. Solution

2.2. Anionic salt is the negative ionAnionic salt is the negative ion

Buffer example - Carbonic AcidBuffer example - Carbonic Acid

COCO22 + H + H2200

ClarificationClarification

Acid PrecipitationAcid Precipitation

Rain, snow, or fog with a pH lower than 5.6Rain, snow, or fog with a pH lower than 5.6

Caused by Caused by pollutants pollutants mixing with water mixing with water in the airin the air