Presentation on theme: "Carbon and the Molecular Diversity of Life"— Presentation transcript:
1Carbon and the Molecular Diversity of Life Chapter 4Carbon and the Molecular Diversity of Life
2Overview: Carbon—The Backbone of Biological Molecules Although cells are 70–95% water, the rest consists mostly of carbon-based compoundsCarbon is unparalleled in its ability to form large, complex, and diverse moleculesProteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds
4Concept 4.1: Organic chemistry is the study of carbon compounds Organic compounds range from simple molecules to colossal onesMost organic compounds contain hydrogen atoms in addition to carbon atomsVitalism, the idea that organic compounds arise only in organisms, was disproved when chemists synthesized the compoundsMechanism is the view that all natural phenomena are governed by physical and chemical laws
6Concept 4.2: Carbon atoms can form diverse molecules by bonding to four other atoms Electron configuration is the key to an atom’s characteristicsElectron configuration determines the kinds and number of bonds an atom will form with other atoms
7The Formation of Bonds with Carbon With four valence electrons, carbon can form four covalent bonds with a variety of atomsThis tetravalence makes large, complex molecules possible
8In 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 molecule has a flat shape
9Molecular Formula Structural Formula Ball-and-Stick Model Space-FillingModelMethaneEthaneEthene (ethylene)
10The 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
12Molecular Diversity Arising from Carbon Skeleton Variation Carbon chains form the skeletons of most organic moleculesCarbon chains vary in length and shapeAnimation: Carbon Skeletons
13(commonly called isobutane) EthanePropaneLengthButane2-methylpropane(commonly called isobutane)Branching1-Butene2-ButeneDouble bondsCyclohexaneBenzeneRings
14HydrocarbonsHydrocarbons 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
16IsomersIsomers are compounds with the same molecular formula but different structures and properties:Structural isomers have different covalent arrangements of their atomsGeometric isomers have the same covalent arrangements but differ in spatial arrangementsEnantiomers are isomers that are mirror images of each otherAnimation: Isomers
17LE 4-7 cis isomer: The two Xs are on the same side. Structural isomers differ in covalent partners, as shown in this example of two isomers of pentane.cis isomer: The two Xsare on the same side.trans isomer: The two Xsare on opposite sides.Geometric isomers differ in arrangement about a double bond. In these diagrams, X represents an atom or group of atoms attached to a double-bonded carbon.L isomerD isomerEnantiomers differ in spatial arrangement around an asymmetric carbon, resulting in molecules that are mirror images, like left and right hands. The two isomers are designated the L and D isomers from the Latin for left and right (levo and dextro). Enantiomers cannot be superimposed on each other.
18Enantiomers are important in the pharmaceutical industry Two enantiomers of a drug may have different effectsDiffering effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in moleculesAnimation: L-Dopa
19(effective against Parkinson’s disease) (biologically Inactive) L-Dopa LE 4-8L-Dopa(effective againstParkinson’s disease)D-Dopa(biologicallyInactive)
20Concept 4.3: Functional groups are the parts of molecules involved in chemical reactions Distinctive properties of organic molecules depend not only on the carbon skeleton but also on the molecular components attached to itCertain groups of atoms are often attached to skeletons of organic molecules
21The Functional Groups Most Important in the Chemistry of Life 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
23The six functional groups that are most important in the chemistry of life: Hydroxyl groupCarbonyl groupCarboxyl groupAmino groupSulfhydryl groupPhosphate group
24FUNCTIONAL PROPERTIES LE 4-10aaSTRUCTURE(may be written HO—)Ethanol, the alcohol present inalcoholic beveragesNAME OF COMPOUNDSFUNCTIONAL PROPERTIESAlcohols (their specific namesusually end in -ol)Is polar as a result of theelectronegative oxygen atomdrawing electrons toward itself.Attracts water molecules, helpingdissolve organic compounds suchas sugars (see Figure 5.3).
25LE 4-10ab STRUCTURE EXAMPLE NAME OF COMPOUNDS Acetone, the simplest ketoneSTRUCTUREEXAMPLEAcetone, the simplest ketonePropanal, an aldehydeNAME OF COMPOUNDSKetones if the carbonyl group iswithin a carbon skeletonFUNCTIONAL PROPERTIESAldehydes if the carbonyl group isat the end of the carbon skeletonA ketone and an aldehyde maybe structural isomers withdifferent properties, as is the casefor acetone and propanal.
26LE 4-10ac STRUCTURE EXAMPLE Acetic acid, which gives vinegar its sour tasteNAME OF COMPOUNDSFUNCTIONAL PROPERTIESCarboxylic acids, or organic acidsHas acidic properties because it isa source of hydrogen ions.The covalent bond betweenoxygen and hydrogen is so polarthat hydrogen ions (H+) tend todissociate reversibly; for example,Acetic acidAcetate ionIn cells, found in the ionic form,which is called a carboxylate group.
27LE 4-10ba STRUCTURE EXAMPLE Glycine Because it also has a carboxyl group, glycine is both an amine anda carboxylic acid; compounds withboth groups are called amino acids.NAME OF COMPOUNDSFUNCTIONAL PROPERTIESAmineActs as a base; can pick up aproton from the surroundingsolution:(nonionized)(ionized)Ionized, with a charge of 1+,under cellular conditions
28STRUCTURE EXAMPLE NAME OF COMPOUNDS LE 4-10bbSTRUCTUREEXAMPLE(may be written HS—)EthanethiolNAME OF COMPOUNDSFUNCTIONAL PROPERTIESThiolsTwo sulfhydryl groups caninteract to help stabilize proteinstructure (see Figure 5.20).
29STRUCTURE EXAMPLE NAME OF COMPOUNDS LE 4-10bcSTRUCTUREEXAMPLEGlycerol phosphateNAME OF COMPOUNDSFUNCTIONAL PROPERTIESOrganic phosphatesMakes the molecule of which itis a part an anion (negativelycharged ion).Can transfer energy betweenorganic molecules.
30ATP: An Important Source of Energy for Cellular Processes One phosphate molecule, adenosine triphosphate (ATP), is the primary energy-transferring molecule in the cellATP consists of an organic molecule called adenosine attached to a string of three phosphate groups
31The Chemical Elements of Life: A Review The versatility of carbon makes possible the great diversity of organic moleculesVariation at the molecular level lies at the foundation of all biological diversity