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Carbon and the Molecular Diversity of Life

发布时间:2013-12-04 13:02:21  



Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

? 2011 Pearson Education, Inc.

Overview: Carbon: The Backbone of Life?Living organisms consist mostly of carbon-based compounds

?Carbon is unparalleled in its ability to form large, complex, and diverse molecules

?Proteins, DNA, carbohydrates, and other

molecules that distinguish living matter are all composed of carbon compounds? 2011 Pearson Education, Inc.

Figure 4.1

Concept 4.1: Organic chemistry is the study of carbon compounds

?Organic chemistryis the study of compounds that contain carbon

?Organic compounds range from simple molecules to colossal ones

?Most organic compounds contain hydrogen atoms in addition to carbon atoms? 2011 Pearson Education, Inc.

?Vitalism, the idea that organic compounds arise only in organisms, was disproved when chemists synthesized these compounds?Mechanismis the view that all natural

phenomena are governed by physical and chemical laws? 2011 Pearson Education, Inc.

Organic Molecules and the Origin of Life on Earth

?Stanley Miller’s classic experiment

demonstrated the abiotic synthesis of organic compounds

?Experiments support the idea that abiotic synthesis of organic compounds, perhaps near volcanoes, could have been a stage in the origin of life? 2011 Pearson Education, Inc.

Figure 4.2EXPERIMENTWater vaporCH4―Atmosphere‖


Cooled ―rain‖containingorganicmoleculesCold waterH2O ―sea‖

Sample for chemical analysis

Concept 4.2: Carbon atoms can form diverse molecules by bonding to four other atoms?Electron configuration is the key to an atom’s characteristics

?Electron configuration determines the kinds and number of bonds an atom will form with other atoms? 2011 Pearson Education, Inc.

The Formation of Bonds with Carbon?With four valence electrons, carbon can form four covalent bonds with a variety of atoms?This ability makes large, complex molecules possible

?In molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shape

?However, when two carbon atoms are joined by a double bond, the atoms joined to the carbons are in the same plane as the carbons? 2011 Pearson Education, Inc.

Figure 4.3

Name andComment(a) MethaneMolecularFormulaStructuralFormulaBall-and-Stick ModelSpace-FillingModel


(b) Ethane


(c) Ethene



?The electron configuration of carbon gives it covalent compatibility with many different elements

?The valences of carbon and its most frequent partners (hydrogen, oxygen, and nitrogen) are the “building code” that governs the architecture of living molecules? 2011 Pearson Education, Inc.

Figure 4.4


(valence ?1)Oxygen(valence ?2)Nitrogen?3)Carbon(valence ?4)(valence

?Carbon atoms can partner with atoms other than hydrogen; for example:

–Carbon dioxide: CO2

–Urea: CO(NH2)2

? 2011 Pearson Education, Inc.

Figure 4.UN01


Molecular Diversity Arising from Carbon Skeleton Variation

?Carbon chains form the skeletons of most organic molecules

?Carbon chains vary in length and shapeAnimation: Carbon Skeletons

? 2011 Pearson Education, Inc.

Figure 4.5

(a) Length

Ethane(b) Branching


(isobutane)(c) Double bond position1-Butene2-Butene(d) Presence of ringsCyclohexaneBenzene

(a) Length

EthanePropaneFigure 4.5a

Figure 4.5b

(b) Branching


(commonly called isobutane)

Figure 4.5c

(c) Double bond position


(d) Presence of rings

CyclohexaneBenzeneFigure 4.5d


?Hydrocarbonsare organic molecules consisting of only carbon and hydrogen

?Many organic molecules, such as fats, have hydrocarbon components

?Hydrocarbons can undergo reactions that release a large amount of energy? 2011 Pearson Education, Inc.

Figure 4.6

NucleusFat droplets

10 ?m

(a) Part of a human adipose cell(b) A fat molecule

Figure 4.6a

NucleusFat droplets10 ?m


?Isomersare compounds with the same

molecular formula but different structures and properties

–Structural isomershave different covalent arrangements of their atoms

–Cis-transisomershave the same covalent bonds but differ in spatial arrangements–Enantiomersare isomers that are mirror images of each otherAnimation: Isomers

? 2011 Pearson Education, Inc.

(a) Structural isomers(b) Cis-transisomerscisisomer: The two Xsare on the same side.(c) Enantiomers




L isomertransisomer: The two Xsare on opposite sides.CO2HNH2HCH3D isomerFigure 4.7

Figure 4.7a

(a) Structural isomers

Figure 4.7b

(b) Cis-transisomerscisisomer: The two Xsare on the same side.transisomer: The two Xsare on opposite sides.

(c) Enantiomers



L isomerCO2HNH2HCH3D isomerFigure 4.7c

?Enantiomers are important in the

pharmaceutical industry

?Two enantiomers of a drug may have different effects

?Usually only one isomer is biologically active?Differing effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in molecules Animation: L-Dopa

? 2011 Pearson Education, Inc.

Figure 4.8








Concept 4.3: A few chemical groups are key to the functioning of biological molecules?Distinctive properties of organic molecules depend on the carbon skeleton and on the molecular components attached to it

?A number of characteristic groups can

replace the hydrogens attached to skeletons of organic molecules? 2011 Pearson Education, Inc.

The Chemical Groups Most Important in the Processes of Life

?Functional groupsare the components of organic molecules that are most commonly involved in chemical reactions

?The number and arrangement of functional groups give each molecule its unique properties ? 2011 Pearson Education, Inc.

Figure 4.UN02



?The seven functional groups that are most important in the chemistry of life:

–Hydroxyl groupCarbonyl groupCarboxyl groupAmino groupSulfhydryl groupPhosphate groupMethyl group? 2011 Pearson Education, Inc.

Figure 4.9-a



(may be written HO—)


COMPOUNDAlcohols (Their specific namesusually end in -ol.)Ketones if the carbonyl group iswithin a carbon skeleton

Aldehydes if the carbonyl group

is at the end of the carbon skeletonCarboxylic acids, or organic acids


EthanolAcetoneAcetic acid



PROPERTIES? Is polar as a result of theelectrons spending more time

near the electronegative oxygen


? Can form hydrogen bonds with

water molecules, helping dissolve

organic compounds such as

sugars.? A ketone and an aldehyde may bestructural isomers with differentproperties, as is the case foracetone and propanal.? Ketone and aldehyde groups arealso found in sugars, giving riseto two major groups of sugars:ketoses (containing ketone

groups) and aldoses (containing

aldehyde groups).? Acts as an acid; can donate anH+because the covalent bondbetween oxygen and hydrogenis so polar:NonionizedIonized

? Found in cells in the ionized form

with a charge of 1?and called a

carboxylate ion.

Figure 4.9-b

(may be

written HS—)

AminesThiolsOrganic phosphatesMethylated compounds


? Acts as a base; can

pick up an H+ from the

surrounding solution

(water, in living

organisms): Cysteine? Two sulfhydryl groups canreact, forming a covalentbond. This ―cross-linking‖helps stabilize proteinstructure.

? Cross-linking of cysteines

in hair proteins maintains

the curliness or straightness

of hair. Straight hair can be

―permanently‖ curled by

shaping it around curlers

and then breaking and

re-forming the cross-linking

bonds.Glycerol phosphate? Contributes negative charge tothe molecule of which it is a part(2–when at the end of a molecule,as above; 1–when locatedinternally in a chain ofphosphates).? Molecules containing phosphategroups have the potential to reactwith water, releasing energy.5-Methyl cytidine? Addition of a methyl groupto DNA, or to moleculesbound to DNA, affects theexpression of genes.? Arrangement of methylgroups in male and femalesex hormones affects theirshape and function.NonionizedIonized? Found in cells in theionized form with a

charge of 1+.

Figure 4.9a


STRUCTUREAlcoholsNAME OFEXAMPLE(Their specific(may be written names usuallyHO—)end in -ol.)?Is polar as a result

of the electronsspending moretime near theelectronegativeoxygen atom.

Ethanol?Can form hydrogen

bonds with watermolecules, helpingdissolve organiccompounds suchas sugars.COMPOUNDFUNCTIONALPROPERTIES

Figure 4.9b


STRUCTUREKetones if the carbonylNAME OFEXAMPLE


Propanalgroup is within aCOMPOUNDcarbon skeletonAldehydes if the carbonylgroup is at the end of thecarbon skeleton?A ketone and anFUNCTIONALaldehyde may bePROPERTIESstructural isomerswith different properties,as is the case foracetone and propanal.?Ketone and aldehydegroups are also foundin sugars, giving riseto two major groupsof sugars: ketoses(containing ketonegroups) and aldoses(containing aldehydegroups).

Figure 4.9c


STRUCTURECarboxylic acids, or organicNAME OFEXAMPLEacids?Acts as an acid; can

donate an H+because thecovalent bond betweenoxygen and hydrogen is sopolar:

Acetic acid

NonionizedIonized?Found in cells in the ionizedform with a charge of 1–andcalled a carboxylate ion. COMPOUNDFUNCTIONALPROPERTIES

Figure 4.9d



Glycine?Acts as a base; canpick up an H+from thesurrounding solution(water, in livingorganisms):

NonionizedIonized?Found in cells in theionized form with acharge of 1?.COMPOUNDFUNCTIONALPROPERTIES

Figure 4.9e



EXAMPLE(may bewritten HS—)

CysteineThiolsNAME OFCOMPOUND?Two sulfhydryl groups canFUNCTIONALreact, forming a covalentPROPERTIESbond. This ―cross-linking‖helps stabilize proteinstructure.?Cross-linking of cysteinesin hair proteins maintainsthe curliness or straightness

of hair. Straight hair can be―permanently‖ curled byshaping it around curlersand then breaking and

re-forming the cross-linkingbonds.

Figure 4.9f



charge to the moleculePROPERTIESof which it is a part(2–when at the end ofa molecule, as at left;1–when located

internally in a chain ofphosphates).

Glycerol phosphate?Molecules containing

phosphate groups havethe potential to reactwith water, releasingenergy.

Figure 4.9g



5-Methyl cytidineMethylated compoundsNAME OFCOMPOUND?Addition of a methyl groupFUNCTIONALto DNA, or to moleculesPROPERTIESbound to DNA, affects theexpression of genes.?Arrangement of methylgroups in male and femalesex hormones affects theirshape and function.

ATP: An Important Source of Energy for Cellular Processes

?One phosphate molecule, adenosine triphosphate(ATP), is the primary energy-transferring molecule in the cell

?ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups? 2011 Pearson Education, Inc.

Figure 4.UN03


Figure 4. UN04


The Chemical Elements of Life: A Review?The versatility of carbon makes possible the great diversity of organic molecules

?Variation at the molecular level lies at the foundation of all biological diversity? 2011 Pearson Education, Inc.

Figure 4. UN05

Reactswith H2O



Figure 4. UN07

Figure 4. UN08

Figure 4. UN09

Figure 4. UN10

Figure 4. UN11

Figure 4. UN12

Figure 4. UN13

Figure 4. UN14

Figure 4. UN15

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