0 4 Carbon and the Molecular Diversity of Life Lecture Presentation by - PowerPoint Presentation

0 4 Carbon and the Molecular Diversity of Life Lecture Presentation by Nicole Tunbridge andKathleen Fitzpatrick

Carbon: The Backbone of LifeLiving organisms consist mostly of carbon-based compoundsCarbon is unparalleled in its ability to form large, complex, and varied moleculesProteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds

Figure 4.1

Figure 4.1a Carbon can bond to four other atoms orgroups of atoms, making a large variety ofmolecules possible.

Concept 4.1: Organic chemistry is the study of carbon compoundsOrganic chemistry is the study of compounds that contain carbonOrganic compounds range from simple molecules to colossal ones Most organic compounds contain hydrogen atoms in addition to carbon atoms

Organic Molecules and the Origin of Life on EarthStanley Miller’s classic experiment demonstrated the abiotic synthesis of organic compoundsExperiments support the idea that abiotic synthesis of organic compounds, perhaps near volcanoes, could have been a stage in the origin of life

Figure 4.2 Water vaporCooled “rain”containingorganicmoleculesSample forchemical analysis Coldwater CondenserElectrode“Atmosphere” CH 4 NH 3 H 2 H 2 O “sea”

Concept 4.2: Carbon atoms can form diverse molecules by bonding to four other atomsElectron configuration is the key to an atom’s characteristicsElectron configuration determines the kinds and number of bonds an atom will form with other atoms

The Formation of Bonds with CarbonWith four valence electrons, carbon can form four covalent bonds with a variety of atomsThis ability makes large, complex molecules possibleIn 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 arein the same plane as the carbons

Figure 4.3 Molecule(a) Methane(b) Ethane(c) Ethene (ethylene) MolecularFormula StructuralFormulaBall-and-Stick Model Space-Filling Model CH 4 C 2 H 6 C 2 H 4

Figure 4.4 Hydrogen(valence = 1)Oxygen(valence = 2)Nitrogen(valence = 3)Carbon (valence = 4)

Carbon atoms can partner with atoms other than hydrogen; for example:Carbon dioxide: CO2 Urea: CO(NH2)2

Figure 4.UN02 Urea

Figure 4.5 (a) Length(b) Branching(d) Presence of rings(c) Double bond positionEthane Propane1-Butene 2-ButeneButane 2-Methylpropane ( isobutane ) Cyclohexane Benzene

Animation: Carbon Skeletons

HydrocarbonsHydrocarbons are organic molecules consisting of only carbon and hydrogenMany organic molecules, such as fats, have hydrocarbon componentsHydrocarbons can undergo reactions that release a large amount of energy

Figure 4.6 Nucleus Fat droplets (b) A fat molecule(a) Part of a human adipose cell10 μ m

IsomersIsomers are compounds with the same molecular formula but different structures and propertiesStructural isomers have different covalent arrangements of their atoms Cis-trans isomers have the same covalent bonds but differ in spatial arrangementsEnantiomers are isomers that are mirror imagesof each other

Figure 4.7 (a) Structural isomers(b) Cis-trans isomersPentanecis isomer: The two Xs areon the same side. 2-methyl butanetrans isomer: The two Xs are on opposite sides. (c) Enantiomers L isomer D isomer CO 2 H CO 2 H H CH 3 CH 3 H NH 2 NH 2 C C

Animation: Isomers

Enantiomers are important in the pharmaceutical industryTwo enantiomers of a drug may have different effectsUsually only one isomer is biologically activeDiffering effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in molecules

Figure 4.8 DrugEffectsEffectiveEnantiomerIneffectiveEnantiomer IbuprofenAlbuterol Reducesinflammationand pain Relaxes bronchial (airway) muscles, improving airflow in asthma patients S -Ibuprofen R - AIbuterol S - AIbuterol R -Ibuprofen

Animation: L-Dopa

Concept 4.3: A few chemical groups are key to molecular functionDistinctive properties of organic molecules depend on the carbon skeleton and on the chemical groups attached to itA number of characteristic groups can replacethe hydrogens attached to skeletons of organic molecules

Figure 4.UN03 EstradiolTestosterone

Functional groups are the components of organic molecules that are most commonly involved in chemical reactionsThe number and arrangement of functional groups give each molecule its unique properties

The seven functional groups that are most important in the chemistry of lifeHydroxyl groupCarbonyl group Carboxyl groupAmino groupSulfhydryl groupPhosphate groupMethyl group

Figure 4.9 Chemical GroupCompound NameExamplesEthanolPropanal AcetoneAcetic acid GlycineCysteine Glycerol phosphate Organic phosphate Thiol Amine Carboxylic acid, or organic acid Ketone Aldehyde Alcohol Hydroxyl group (—OH) Carboxyl group (—COOH) Amino group (—NH 2 ) Sulfhydryl group (—SH) Phosphate group (—OPO 3 2− ) Methyl group (—CH 3 ) Methylated compound 5-Methyl cytosine Carbonyl group ( C＝O) — —

Figure 4.9aa Ethanol, the alcoholpresentin alcoholicbeveragesPolar due to electronegative oxygen. Forms hydrogen bonds with water.Compound name: AlcoholHydroxyl group (—OH) (may be written HO—)

Figure 4.9ab Propanal,an aldehydeAcetone,the simplest ketoneSugars with ketone groups are called ketoses; those with aldehydesare called aldoses.Compound name: Ketone or aldehyde Carbonyl group ( C＝O)— —

Figure 4.9ac Acetic acid, whichgives vinegar itssour tasteActs as an acid.Compound name: Carboxylic acid, or organic acidCarboxyl group (—COOH)Ionized form of —COOH (carboxylate ion),found in cells

Figure 4.9ad Glycine, an amino acid(note its carboxyl group)Acts as a base.Compound name: AmineAmino group (—NH2)Ionized form of —NH2,found in cells

Figure 4.9ba Cysteine, a sulfur-containing amino acidTwo —SH groups can react, forming a “cross-link” that helps stabilizeprotein structure.Compound name: ThiolSulfhydryl group (—SH) (may be written HS—)

Figure 4.9bb Glycerol phosphate,which takes part inmany importantchemical reactions incellsContributes negative charge. When attached, confers on a molecule the abilityto react with water, releasing energy.Compound name: Organic phosphatePhosphate group (—OPO 32−)

Figure 4.9bc Methyl group (—CH3)Affects the expression of genes. Affects the shape and function ofsex hormones.Compound name: Methylated compound5-Methyl cytosine, acomponent of DNAthat has been modified by addition of a methylgroup

The Chemical Elements of Life: A ReviewThe versatility of carbon makes possible the great diversity of organic moleculesVariation at the molecular level lies at the foundation of all biological diversity

Figure 4.UN06

Figure 4.UN07

Figure 4.UN08 a b c d e