Chapter 3.ppt

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Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures forBiology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 3

ater and the !itness o"

the En#ironment


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Overview: The Molecule That Supports All of

Life$ Water is the biological medium here on arth

$ All living organisms re!uire water more than

an" other substance


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Three#!uarters of the arth$s surface is

submerged in water The abundance of water is the main reason the

arth is habitable

Figure 3.1


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%oncept &'(: The polarity of water molecules

results in hydrogen bonding The water molecule is a polar molecule


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The polarit" of water molecules

$ Allows them to form h"drogen bonds with eachother

$ %ontributes to the various properties water

e)hibits

*"drogen

bonds

+

+

*

*+

+

,

,

,,

Figure 3.2


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%oncept &'-: .our emergent propertiesof water

contribute to arth$s fitness for life


7/34Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Cohesion (1)

Water molecules e)hibit cohesion

%ohesion

$ /s the bonding of a high percentage of the

molecules to neighboring molecules

$ /s due to h"drogen bonding



%ohesion

$ *elps pull water up through the microscopicvessels of plants

Water conducting cells

(00 mFigure 3.3



Surface tension

$ /s a measure of how hard it is to brea1 thesurface of a li!uid

$ /s related to cohesion

Figure 3.4



Moderation of Temperature (2)

Water moderates air temperature

$ 2" absorbing heat from air that is warmer andreleasing the stored heat to air that is cooler



Heat and Temperature

3inetic energ"

$ /s the energ" of motion



*eat

$ /s a measure of the total amount of 1ineticenerg" due to molecular motion

Temperature

$ Measures the intensit" of heat



Waters High pecific Heat

The specific heatof a substance

$ /s the amount of heat that must be absorbed orlost for 1 gram of that substance to change its

temperature by 1C


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Water has a high specific heat4 which allows it

to minimi5e temperature fluctuations to withinlimits that permit life

$ *eat is absorbed when h"drogen bonds brea1

$ *eat is released when h"drogen bonds form


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!"aporati"e Coo#ing

vaporation

$ /s the transformation of a substance from ali!uid to a gas


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Heat of vaporization

$ /s the quantity of heat a liquid must absorb for 1gram of it to be converted from a liquid to a gas


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vaporative cooling

$ /s due to water$s high heat of vapori5ation

$ Allows water to cool a surface


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$nsu#ation of %odies of Water by oating $ce

Solid water4 or ice e)pands upon cooling 6&7

$ /s less dense than li!uid water

$ .loats in li!uid water


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The h"drogen bonds in ice

$ Are more 8ordered9 than in li!uid water4 ma1ingice less dense

i!uid water

*"drogen bondsconstantl" brea1 and re#form

"ce

*"drogen bonds are stable

*"drogenbond

Figure 3.#


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Since ice floats in water

$ Life can e)ist under the fro5en surfaces ofla1es and polar seas


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The o#"ent of Life (')

Water is a versatile solvent due to its polarit"

/t can form a!ueous solutions


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The different regions of the polar water

molecule can interact with ionic compoundscalled solutes and dissolve themegative

o)"gen regions

of polar water molecules

are attracted to sodium

cations 6a+7'

+

+

+

+%l ,

,

,

,

,

a+Positive

h"drogen regions

of water molecules

cling to chloride anions

6%l,7'

+

+

+

+

,

,

,

,

,

,

a+

%l,

Figure 3.$


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Water can also interact with polar molecules

such as proteins

This o)"gen is

attracted to a slight

positive charge on

the l"so5"me

molecule'This o)"gen is attracted to a slight

negative charge on the l"so5"me

molecule'%a&L"so5"me molecule

in a nona!ueous

environment

%b& L"so5"me molecule 6purple7

in an a!ueous environment

such as tears or saliva

%c& /onic and polar regions on the protein$s

Surface attract water molecules'

+

,

Figure 3.'


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Hydrophi#ic and Hydrophobic ubstances

A h"drophilic substance

$ *as an affinit" for water


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A h"drophobic substance

$ ;oes not have an affinit" for water


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o#ute Concentration in ueous o#utions

Since most biochemical reactions occur in

water$ /t is important to learn to calculate the

concentration of solutes in an a!ueous solution


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A mole

$


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%oncept &'&: ;issociation of water molecules

leads to acidic and basic conditions that affect

living organisms


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Water can dissociate

$ /nto h"dronium ions and h"dro)ide ions

%hanges in the concentration of these ions

$ %an have a great affect on living organisms

*

*"droniumion 6*&O

+7

*

*"dro)ideion 6O*,7

*

*

*

*

*

*

+ ,

+

Figure on p. #3 of water

dissociating


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cids and %ases

An acid

$ /s an" substance that increases the h"drogenion concentration of a solution

A base

$ /s an" substance that reduces the h"drogen

ion concentration of a solution


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The pH ca#e

The p* of a solution

$ /s determined b" the relative concentration ofh"drogen ions

$ p* is low in an acid 6high *+ concentration7

$ p* is high in a base 6low *+ concentration7


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The p* scale and p* values of various

a!ueous solutions

/ncreasingl"(cidic

=*+>

?=O*,>

/ncreasingl")a

sic

=*+>@=O*,>

*eutral

=*+> =O*,>

Oven cleaner

0

(

-

&

B

C

D

E

F

G(0

((

(-

(&

(B

pH +cale

2atter" acid

;igestive 6stomach7Huice4 lemon HuiceIinegar4 beer4 wine4

colaTomato Huice

2lac1 coffee


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%uffers

The internal p* of most living cells

$ Must remain close to p* E


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2uffers

$ Are substances that minimi5e changes in theconcentrations of h"drogen and h"dro)ide ions

in a solution

$ %onsist of an acid#base pair that reversibl"combines with h"drogen ions

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