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2013 Pearson Education, Inc.Lectures by Edward J. Zalisko

PowerPointLectures forCampbel l Essent ia l Biology, Fifth Edition,and

Campbel l Essent ia l Biolog y with Phys io logy,

Fourth Edition

Eric J. Simon, Jean L. Dickey, and Jane B. Reece

Chapter 2Essential Chemistry for Biology


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Biology and Society:

More Precious than Gold

A drought is

a period of abnormally dry weather that changes

the environment and

one of the most devastating disasters.

2013 Pearson Education, Inc.


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Figure 2.0


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Droughts can cause

severe crop damage,

shortages of drinking water,

dust storms,

famine,

habitat loss, and

mass migration.





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Throughout human history, droughts have helpedwipe out societies and even whole civilizations.

Droughts are catastrophic because life cannot exist

without water.





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SOME BASIC CHEMISTRY

Take any biological system apart, and you

eventually end up at the chemical level.

Chemical reactions are always occurring in the

human body.



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Matter: Elements and Compounds

Matteris anything that occupies space and has

mass.

Matter is found on Earth in three physical states:

solid,

liquid, and

gas.



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Matter is composed of chemical elements.

An element is a substance that cannot be broken

down into other substances by chemical reactions.

There are 92 naturally occurring elements onEarth.

All of the elements are listed in the periodic table.




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Figure 2.1a

Atomic number

(number of protons)

Mass number

(number of

protons plus neutrons)

Element symbol

12

6

C

He

Ne

Se Br

Cl

F

Ar

Kr

Xe

ONCB

SPSiAl

I

Ge AsGa

TeSbSnIn

MnCr

Po At RnPb BiTI

CoFeV CuNi Zn

Tm Yb LuHo ErDy

BeLi

MgNa

K ScCa Ti

MoNb RuTc PdRh AgYSrRb Zr

H

Cd

LaBa TaHf OsRe IrW AuPt HgCs

BhSg MtHs RgDs CnFr AcRa Rf Db

Md No LrEs FmCfAm Cm BkNp PuU

Eu Gd TbPm SmNd

Pa

Pr

Th

Ce


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Figure 2.1b

Mercury (Hg)

Fi 2 1


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Figure 2.1c

Copper (Cu)

Fi 2 1d


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Figure 2.1d

Lead (Pb)


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Twenty-five elements are essential to people.

Four elements make up about 96% of the weight of

most cells:

oxygen,

carbon,

hydrogen, and

nitrogen.



Figure 2 2


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Figure 2.2

Oxygen (O):65.0%

Carbon (C): 18.5%

Calcium (Ca): 1.5%

Magnesium (Mg): 0.1%

Chlorine (Cl): 0.2%

Sodium (Na): 0.2%

Sulfur (S): 0.3%

Potassium (K): 0.4%

Phosphorus (P): 1.0%

Hydrogen (H):

9.5%

Nitrogen (N):

3.3%

Trace elements: less than 0.01%

Iron (Fe)

Iodine (I)Fluorine (F)

Copper (Cu)Cobalt (Co)Chromium (Cr)

Boron (B)

Zinc (Zn)

Vanadium (V)Tin (Sn)

Silicon (Si)Selenium (Se)Molybdenum (Mo)

Manganese (Mn)


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Trace elements are

required in only very small amounts and

essential for life.

An iodine deficiency causes goiter.

Fluorine

is added to dental products and drinking water and

helps to maintain healthy bones and teeth.



Figure 2 3


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Figure 2.3


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Elements can combine to form compounds.

Compounds are substances that contain two or

more elements in a fixed ratio.

Common compounds include NaCl (table salt) and

H2O (water).




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Atoms

Each element consists of one kind of atom.

An atom is the smallest unit of matter that still

retains the properties of an element.



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The Structure of Atoms

Atoms are composed of subatomic particles.

A proton is positively charged.

An electron is negatively charged.

A neutron is electrically neutral.

Most atoms have protons and neutrons packed

tightly into the nucleus.

The nucleus is the atoms central core.

Electrons orbit the nucleus.


Figure 2 4


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Figure 2.4

Nucleus 2e

Electron cloud

Nucleus

Electrons

Neutrons

Protons

2

2

2


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Elements differ in the number of subatomic

particles in their atoms.

The number of protons, the atomic number,

determines which element it is.

Mass is a measure of the amount of material in

an object.

An atoms mass numberis the sum of the

number of protons and neutrons in its nucleus.

The Structure of Atoms



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I sotopes

Isotopes are alternate mass forms of an element.

Isotopes

have the same number of protons and electrons

but

differ in their number of neutrons.


Table 2.1


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Table 2.1


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The nucleus of a radioactive isotope decays

spontaneously, giving off particles and energy.

Radioactive isotopes have many uses in research

and medicine.

They can be used to determine the fate of atoms in

living organisms.

They are used in PET scans to diagnose heart

disorders and some cancers.

I sotopes


Figure 2.5


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g


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Uncontrolled exposure to radioactive isotopes can

harm living organisms by damaging DNA.

The 1986 Chernobyl nuclear accident released

large amounts of radioactive isotopes.

Naturally occurring radon gas may cause lung

cancer.

I sotopes


C


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Electron Arrangement and the Chemical Proper ties

of Atoms

Of the three subatomic particles, only electrons aredirectly involved in the chemical activity of an atom.

Electrons orbit the nucleus of an atom in specific

electron shells.

The farther an electron is from the nucleus, the

greater its energy.

The number of electrons in the outermost shelldetermines the chemical properties of an atom.


Figure 2.6


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Electron

First electron shell

(can hold 2 electrons)Outer electron shell

(can hold 8 electrons)

Hydrogen (H)

Atomic number 1Carbon (C)

Atomic number 6Nitrogen (N)

Atomic number 7Oxygen (O)

Atomic number 8

Ch i l B di d M l l


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Chemical Bonding and Molecules

Chemical reactions enable atoms to give up or

acquire electrons, completing their outer shells.

Chemical reactions usually result in atoms

staying close together and

being held together by attractions called chemical

bonds.


I i B d


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I onic Bonds

When an atom loses or gains electrons, it becomes

electrically charged.

Charged atoms are called ions.

Ionic bonds are formed between oppositelycharged ions.



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Animation: Ionic Bonds

Right-click slide / select play

Figure 2.7-1


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Na

Sodium atom

Cl

Chlorine atom

Na Cl

Figure 2.7-2


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Completeouter shells

Sodium chloride (NaCl)

Cl

Chloride ion

Na Cl

Na

Sodium atom

Cl

Chlorine atom

Na Cl

Na

Sodium ion

Covalent Bonds


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Covalent Bonds

A covalent bond forms when two atoms share one

or more pairs of outer-shell electrons.

Covalent bonds are the strongest of the variousbonds.

Covalent bonds hold atoms together in a molecule.

The number of covalent bonds an atom can form isequal to the number of additional electrons needed

to fill its outer shell.



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Blast Animation: Covalent Bonds



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Animation: Covalent Bonds


Figure 2.8


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Electron configuration Structural formula

Hydrogen gas (H2)

Space-filling model

Oxygen gas (O2)

Methane (CH4)

H H

H

O O

H

H HC

Ball-and-stick model

Hydrogen Bonds


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Hydrogen Bonds

Water is a compound in which the electrons in its

covalent bonds are not shared equally.

This causes water to be a polar molecule, one

with an uneven distribution of charge.



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Blast Animation: Hydrogen Bonds in Water


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Animation: Water Structure


Figure 2.UN01


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O

H H

Figure 2.UN02


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O

H H(slightly ) (slightly )

(slightly )

Hydrogen Bonds


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The polarity of water results in weak electrical

attractions between neighboring water molecules.

These weak attractions are called hydrogen

bonds.

Hydrogen Bonds


Figure 2.9


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Hydrogen bond

Slightly

positivecharge

Slightlynegativecharge

Chemical Reactions


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Chemical Reactions

Cells constantly rearrange molecules by breaking

existing chemical bonds and forming new ones.

Such changes in the chemical composition of

matter are called chemical reactions.

A simple example is the reaction between oxygen

gas and hydrogen gas that forms water.


Figure 2.UN03


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Reactants

2 H2O

Oxygen

gas

Hydrogen

gas

Products

Water

2 H2 O2+

Chemical Reactions


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Chemical reactions include

reactants, the starting materials, and

products, the end materials.

Chemical reactions

can rearrange matter

but cannot create or destroy matter.

Chemical Reactions


WATER AND LIFE


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WATER AND LIFE

Life on Earth began in water and evolved there for

3 billion years.

Modern life remains tied to water.

Your cells are composed of 7095% water. The abundance of water is a major reason Earth is

habitable.


Figure 2.10


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Waters Life-Supporting Properties


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Water s Life Supporting Properties

The polarity of water molecules and the hydrogen

bonding that results explain most of waters life-supporting properties.

Water molecules stick together.

Water has a strong resistance to change in

temperature.

Frozen water floats.

Water is a common solvent for life.


The Cohesion of Water


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e Co es o o ate

Water molecules stick together as a result of

hydrogen bonding.

This tendency of molecules of the same kind to

stick together is called cohesion.

Cohesion is vital for the transport of water from the

roots to the leaves of plants.



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Animation: Water Transport


Figure 2.11


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Cohesion due tohydrogen bondsbetween watermolecules

Microscopic water-conducting tubes

Co

lorized

SE

M

Evaporation from the leaves

The Cohesion of Water


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Surface tension is the measure of how difficult it is

to stretch or break the surface of a liquid.

Hydrogen bonds give water an unusually high

surface tension.


Figure 2.12


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How Water Moderates Temperature


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p

Because of hydrogen bonding, water has a strong

resistance to temperature change.

Heat and temperature are related, but different.

Heat is the amount of energy associated with themovement of the atoms and molecules in a body of

matter.

Temperature measures the intensity of heat.

Water can absorb and store large amounts of heat

while only changing a few degrees in temperature.


How Water Moderates Temperature


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Water can moderate temperatures.

Earths giant water supply causes temperatures to

stay within limits that permit life.

Evaporative cooling occurs when a substance

evaporates and the surface of the liquid remaining

behind cools down.

p


Figure 2.13


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The Biological Signif icance of I ce F loating


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When water molecules get cold enough, they move

apart, forming ice.

A chunk of ice has fewer water molecules than an

equal volume of liquid water.

Ice floats because it is less dense than liquid

water.


Figure 2.14


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Stable hydrogen bonds

hold molecules apart,making ice less densethan water.

Hydrogen bond

IceHydrogen bonds

constantly breakand re-form.

Liquid water

The Biological Signi f icance of I ce F loating


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If ice did not float, ponds, lakes, and even the

oceans would freeze solid.

Life in water could not survive if bodies of water

froze solid.

g g g


Water as the Solvent of L ife


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A solution is a liquid consisting of a homogeneous

mixture of two or more substances.

The dissolving agent is the solvent.

The dissolved substance is the solute.

When water is the solvent, the result is an

aqueoussolution.


Figure 2.15


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Chloride ionin solution

Sodium ion

in solution

Salt crystal

NaCl

NaCl

The Process of Science:


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Observation: Human brains shrink as we age. Question: Can aerobic exercise slow or reverse

brain loss?

Hypothesis: MRI scans will reveal differencesbetween people who regularly exercised

aerobically and those who did not.

Can Exercise Boost Your Brain Power?


Figure 2.UN04


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The Process of Science:


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Prediction: Brains of active people shrink lessthan the brains of less active people.

Experiment: Twenty-nine people in their 60s and

70s exercised for three one-hour sessions per

week. A control group of 29 people engaged in

non-aerobic stretching exercises for the same

periods.

Results: The aerobic group showed significant

increases in brain volume compared to the non-

aerobic group.

Can Exercise Boost Your Brain Power?


Figure 2.16


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Acids, Bases, and pH


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A chemical compound that releases H+ to a

solution is an acid.

A compound that accepts H+ and removes them

from solution is a base.

To describe the acidity of a solution, chemists use

the pH scale.


Figure 2.17

Oven cleaner

14


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OH

OH

OHOH

OH

OHH

H

OH

OHOH

OH H

H

H

H

OHOH HH

HH

HH

[H] [OH]

Oven cleaner

Milk of magnesia

Household ammonia

Householdbleach

Seawater

Tomato juice

Black coffee

Urine

Pure water

Human blood

Lemon juice,stomach acidBattery acid

Grapefruit juice,soft drink

pH scale0

1

2

3

4

5

6

7

8

9

10

11

12

13

LowerH

con

centration

GreaterHc

oncentration

Basicsolution

Neutralsolution

Acidicsolution

Figure 2.17a


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OH

OH

OH

OH

OH

OHH

H

Basicsolution

OH

OH

OHOH

H

H

H

H

OH

OHH

H

H

H

H

H

Neutralsolution Acidicsolution

Acids, Bases, and pH


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Buffers are substances that resist pH change.

Buffers

accept H+ ions when they are in excess and

donate H+ ions when they are depleted.

Increases in global CO2 concentrations may lead to

the acidification of the oceans and

ecological disasters.


Figure 2.18


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Evolution Connection:


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The Search for Extraterrestrial Life

If life similar to ours has evolved elsewhere in theuniverse, then it too would depend upon water.

Researchers at NASA missions have found

evidence that water was once abundant on Mars.

Microbial life may exist below the Martian surface.


Figure 2.19


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