www.cengage.com/chemistry/brown

Albia Dugger • Miami Dade College

Cecie StarrChristine EversLisa Starr

Chapter 1Invitation to Biology

Space fish

Milk fish

Hagfish

Puffer

• Life defies a simple, one-sentence definition• Life is recognized by what living things do

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

LIFE

Order

Evolutionary adaptation

Responseto theenvironment

Reproduction

Growth anddevelopment

Energyprocessing

Regulation

Biology The scientific and systematic study of life

Biologists think about life at different levels of organization

The biosphere

Communities

Populations

Organisms

Ecosystems

Organs and organ systems

Cells

Cell

Organelles

Atoms

MoleculesTissues

10 µm

1 µm

50 µm

The biosphere

Communities

Populations

Organisms

Ecosystems

Organs and organ systems

Cells

Cell

Organelles

Atoms

MoleculesTissues

10 µm

1 µm

50 µm

• atom – Fundamental building block of all matter

• molecule – An association of two or more atoms

• organelle– Functional components that make up cells

• cell – Smallest unit of life

• tissue – In multicelled organisms, specialized cells organized in

a pattern that allows them to perform a collective function

• organ – In multicelled organisms, a grouping of tissues that

perform a collective function

• organ system – In multicelled organisms, set of tissues and cells

engaged in a collective function that keeps the body functioning properly

• organism – Individual that consists of one or more cells

• A population is a group of individuals of a species in a given area

• A community is all populations of all species in a given area

• An ecosystem is a community interacting with its environment

• The biosphere includes all regions of Earth that hold life

Species Genus Family Order Class Phylum Kingdom Domain

Ursus americanus(American black bear)

Ursus

Ursidae

Carnivora

Mammalia

Chordata

Animalia

Eukarya

1 µmOrganelles

Nucleus (contains DNA)

Cytoplasm

Membrane

DNA(no nucleus)

Membrane

Eukaryotic cellProkaryotic cell

Nucleus DNA

Cell

Nucleotide

(a) DNA double helix (b) Single strand of DNA

NucleicontainingDNA

Sperm cell

Egg cell

Fertilized eggwith DNA fromboth parents

Embryo’s cells withcopies of inherited DNA

Offspring with traitsinherited fromboth parents

• DNA contains information that guides all of an organism’s metabolic activities, including growth, development, and reproduction

• Small variations in DNA structure give rise to differences between species and individuals

• The passage of DNA from parents to offspring is inheritance

• DNA – Deoxyribonucleic acid; carries hereditary information

that guides growth and development

• growth – In multicelled species, an increase in the number, size,

and volume of cells

• development – Multistep process by which the first cell of a new

individual becomes a multicelled adult

• reproduction – Processes by which parents produce offspring

• inheritance – Transmission of DNA from parents to offspring

Outer membraneand cell surface

Cytoplasm

Nucleus

Negativefeedback

Excess Dblocks a step

D

D D

A

B

C

Enzyme 1

Enzyme 2

Enzyme 3

D

(a) Negative feedback

W

Enzyme 4

XPositivefeedback

Enzyme 5

Y

+

Enzyme 6

Excess Zstimulates astep

ZZ

Z

Z

(b) Positive feedback

Charles Darwin

Populationwith variedinherited traits.

Eliminationof individualswith certaintraits.

Reproductionof survivors.

Increasingfrequencyof traits that enhance survival and reproductive success.

4321

www.cengage.com/chemistry/brown

Albia Dugger • Miami Dade College

Cecie StarrChristine EversLisa Starr

Chapter 2Life’s Chemical Basis

Start With Atoms

• At life’s first level of organization, atoms interact with other atoms to form molecules

• The properties of molecules depend on, but differ from, those of their atomic components

• The behavior of elements, which make up all living things, depends on the structure of individual atoms

• nucleus – Core of an atom; occupied by protons and neutrons

• proton – Positively charged subatomic particle that occurs in

the nucleus of all atoms

• neutron – Uncharged subatomic particle in the atomic

nucleus

• electron – Negatively charged subatomic particle that

occupies orbitals around an atomic nucleus

• Isotopes are atoms of an element that differ in mass number

• isotopes – Forms of an element that differ in the

number of neutrons their atoms carry

• mass number – Total number of protons and neutrons in the

nucleus of an element’s atoms

• radioisotope – Isotope with an unstable nucleus that

spontaneously emit subatomic particles or energy by the process of radioactive decay

• radioactive decay – Process by which atoms of a radioisotope

emit energy and/or subatomic particles when their nucleus spontaneously disintegrates, which can transform one element onto another

• tracer – Molecule labeled with a detectable

substance that track biological processes inside living organisms

Cancerousthroattissue

PET, positron-emission tomography

(a) A ball bouncing down a flight of stairs provides an analogy for energy levels of electrons

Third shell (highest energylevel)

Second shell (higherenergy level)

Energyabsorbed

First shell (lowest energylevel)

Atomicnucleus

(b)

Energylost

Periodic table

Hydrogen

1H

Lithium

3LiBeryllium

4BeBoron

5BCarbon

6CNitrogen

7NOxygen

8OFluorine

9FNeon

10Ne

Helium

2HeAtomic number

Element symbol

Electron-distributiondiagram

Atomic mass

2He

4.00Firstshell

Secondshell

Thirdshell

Sodium

11NaMagnesium

12MgAluminum

13AlSilicon

14SiPhosphorus

15PSulfur

16SChlorine

17ClArgon

18Ar

• shell model – Model of electron distribution in an atom that help

us visualize how electrons populate atoms from the innermost shell outward

• Concentric circles represent successive energy levels– 1st shell: up to 2 electrons– 2nd shell: up to 8 electrons– 3rd shell: up to 8 electrons

• ion – Charged atom

• electronegativity – Measure of the ability of an atom to pull electrons

away from other atoms

Why Atoms Interact

• The characteristics of a bond arise from the properties of atoms that take part in it

• Atoms form different types of bonds depending on their electronegativity– Ionic bonds– Covalent bonds– Hydrogen bonds– Van der Waals interaction

Ionic Bonds

• An ionic bond is a strong association between oppositely charged ions that arises from the mutual attraction of opposite charges

• ionic bond – Type of chemical bond in which a strong

mutual attraction forms between ions of opposite charge

Covalent Bonds

• Atoms share a pair of electrons in a covalent bond, which is nonpolar if the sharing is equal, and polar if it is not

• covalent bond – Chemical bond in which two atoms share a pair of

electrons

• polarity – Any separation of charge into distinct positive and

negative regions

2, 3, or 4 covalent bonds may form between two atoms when they share multiple electrons

Molecular oxygen: O=OMolecular nitrogen: (N=N)

Hydrogen Bonds

• Hydrogen bonds collectively stabilize the structures of large molecules

• hydrogen bond – Attraction that forms between a covalently

bonded hydrogen atom and another atom taking part in a separate covalent bond

Water’s Life-Giving Properties• Water is essential to life because of its

unique properties:– Solvent for salts and other polar solutes– Resists temperature changes– Cohesion

• Unique properties of water result from extensive hydrogen bonding among water molecules

Water Is an Excellent Solvent• Water is a solvent that easily dissolves

salts, sugars, and other polar substances

• solvent – Liquid that can dissolve other substances

• solute – A dissolved substance

Hydrophilic and Hydrophobic

• Hydrophilic substances dissolve easily in water; hydrophobic substances do not

• hydrophilic – Substance that dissolves easily in water,

such as salt

• hydrophobic – Substance that resists dissolving in water,

such as oil

• Ice forms below about 0°C (32°F) floats because the molecules pack less densely than in water

• evaporation – Transition of a liquid to a gas – Requires energy (removes heat from liquid)

Water resists changing its temperature because of its high specific heat

• High specific heat

Cohesion• Hydrogen bonds cause water molecules to resist

separating from each other

• Cohesion

– Tendency of molecules to stick together – Pulls water upward in plants– Causes surface tension

• Adhesionan attraction between different substances, for example, between water and plant cell walls

Neutral solution

Acidic solution

Basic solution

OH–

OH–

OH–

OH–

OH–OH–OH–

H+

H+

H+

OH–

H+ H+

H+ H+

OH–

OH–

OH–OH–

H+

OH–

H+

H+

H+

H+

H+

H+

H+

OH–

Neutral [H+] = [OH–]

Incr

easi

ngly

Aci

dic

[H+ ]

> [O

H– ]

Incr

easi

ngly

Bas

ic [H

+ ] <

[OH

– ]

pH Scale0

1

2

3

4

5

6

7

8

Battery acid

Gastric juice,lemon juice

Vinegar, beer,wine, cola

Tomato juice

Black coffee

RainwaterUrine

SalivaPure waterHuman blood, tears

Seawater

9

10Milk of magnesia

Household ammonia

Householdbleach

Oven cleaner

11

12

13

14

Acids and Bases

• Most biological processes occur within a narrow range of pH, typically around pH 7

• pH – Measure of

concentration of hydrogen ions (H+) in a fluid

• concentration – Number of molecules

or ions of a solute per unit volume of a solution

Buffers• A buffer keeps a solution within a

consistent range of pH

• Most cell and body fluids are buffered because most molecules of life work only within a narrow range of pH

• buffer – Set of chemicals that stabilize pH of a

solution by alternately donating and accepting ions that contribute to pH

The Bicarbonate Buffer System• Carbon dioxide gas becomes a weak acid when it

dissolves in the fluid portion of human blood:

H2O + CO2 (carbon dioxide) → H2CO3 (carbonic acid)

• Carbonic acid separates into hydrogen ions and bicarbonate ions, which can separate into hydrogen ions and carbonate ions :

H2CO3 (carbonic acid) ↔ H+ + HCO3-

(bicarbonate) ↔ H+ + H+ + CO3 -

2

Bicarbonate Buffer System (cont.)

• Exchange of ions between carbonic acid and bicarbonate keeps blood pH between 7.3 and 7.5 – up to a point

• Buffer failure can be catastrophic in a biological system

• Example: Too much carbonic acid forms in blood when breathing is impaired suddenly – the resulting decline in blood pH may cause coma

Fig. 3-10

Moreacidic

0

AcidrainAcidrain

Normalrain

Morebasic

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1011121314

Fig. 3-11

EXPERIMENT

RESULTS

Calc

ifica

tion

rate

(mm

ol C

aCO

3pe

r m2 p

er d

ay)

[CO32–] (µmol/kg)

150 200 250 3000

20

40

Water vapor

H 2NH

3

“Atmosphere”

Electrode

Condenser

Coldwater

Cooled watercontainingorganicmolecules

Sample forchemical analysis

H2O“sea”

EXPERIMENT

CH4

Long Nose Butterfly

Flatfish