1. Chapter 4 Carbon and the Molecular Diversity of Life

2. Carbon & Biological Molecules Although cells are 70–95% water, the rest consists mostly of carbon-based compounds Carbon can form large, complex, and diverse molecules Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds

3. Organic chemistry study of carbon compounds Vitalism = idea that organic compounds arise only in organisms (disproven) Mechanism = view that all natural phenomena are governed by physical and chemical laws

4. Carbon can bonding to four other atoms Electron configuration ~ 4 valence electrons 1s 2 2s 2 2p 2 carbon can form four covalent bonds = “tetravalence” most frequent partners: H, O, N shapes: tetrahedral (4 single bonds), bent, or linear

5. LE 4-3 Molecular Formula Structural Formula Ball-and-Stick Model Space-Filling Model Methane Ethane Ethene (ethylene)

6. Carbon Skeleton Variation chains form the skeletons of most organic molecules Carbon chains vary in: Length Bonds types Shape (branched or rings) Animation: Carbon Skeletons Animation: Carbon Skeletons

7. LE 4-5 Length Ethane Propane Butane 2-methylpropane (commonly called isobutane) Branching Double bonds Rings 1-Butene2-Butene CyclohexaneBenzene

8. Hydrocarbons Hydrocarbons = consist of only C & H Many organic molecules, such as fats, have hydrocarbon components Hydrocarbons can undergo reactions that release a large amount of energy

9. Isomers Isomers = compounds with the same molecular formula but different structures and properties: Structural isomers have different covalent arrangements of their atoms Animation: Isomers Animation: Isomers

10. Geometric isomers have the same covalent arrangements but differ in spatial arrangements

11. Isomers Enantiomers are isomers that are mirror images of each other

12. Enantiomers are important in the pharmaceutical industry Two enantiomers of a drug may have different effects Differing effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in molecules Investigation: L-Dopa Investigation: L-Dopa (effective against Parkinson’s disease) D -Dopa (biologically Inactive)

13. Functional groups Functional groups are attached to carbon skeleton & are the components most commonly involved in chemical reactions The number and arrangement of functional groups give each molecule its unique properties

14. LE 4-9 Estradiol Testosterone Male lion Female lion

15. Hydroxyl group Carbonyl group Carboxyl group Amino group Sulfhydryl group Phosphate group 6 Functional groups

16. LE 4-10aa STRUCTURE (may be written HO—) NAME OF COMPOUNDS Alcohols (their specific names usually end in -ol) Ethanol, the alcohol present in alcoholic beverages FUNCTIONAL PROPERTIES Is polar as a result of the electronegative oxygen atom drawing electrons toward itself. Attracts water molecules, helping dissolve organic compounds such as sugars (see Figure 5.3).

17. LE 4-10ab STRUCTURE NAME OF COMPOUNDS Ketones if the carbonyl group is within a carbon skeleton EXAMPLE Acetone, the simplest ketone A ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal. Aldehydes if the carbonyl group is at the end of the carbon skeleton Acetone, the simplest ketone Propanal, an aldehyde FUNCTIONAL PROPERTIES

18. LE 4-10ac STRUCTURE NAME OF COMPOUNDS Carboxylic acids, or organic acids EXAMPLE Has acidic properties because it is a source of hydrogen ions. Acetic acid, which gives vinegar its sour taste FUNCTIONAL PROPERTIES The covalent bond between oxygen and hydrogen is so polar that hydrogen ions (H + ) tend to dissociate reversibly; for example, Acetic acidAcetate ion In cells, found in the ionic form, which is called a carboxylate group.

19. LE 4-10ba STRUCTURE NAME OF COMPOUNDS Amine EXAMPLE Because it also has a carboxyl group, glycine is both an amine and a carboxylic acid; compounds with both groups are called amino acids. FUNCTIONAL PROPERTIES Acts as a base; can pick up a proton from the surrounding solution: (nonionized) Ionized, with a charge of 1+, under cellular conditions Glycine (ionized)

20. LE 4-10bb STRUCTURE (may be written HS—) NAME OF COMPOUNDS Thiols EXAMPLE Ethanethiol FUNCTIONAL PROPERTIES Two sulfhydryl groups can interact to help stabilize protein structure (see Figure 5.20).

21. LE 4-10bc STRUCTURE NAME OF COMPOUNDS Organic phosphates EXAMPLE Glycerol phosphate FUNCTIONAL PROPERTIES Makes the molecule of which it is a part an anion (negatively charged ion). Can transfer energy between organic molecules.