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CHAPTER 4

CHAPTER 4. CARBON AND THE MOLECULAR DIVERSITY OF LIFE. Overview: Carbon—The Backbone of Life. Aside from water, the most biologically important molecules are carbon-based (organic). Although cells are 70–95% water, the rest consists mostly of carbon-based compounds

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CHAPTER 4

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  1. CHAPTER 4 CARBON AND THE MOLECULAR DIVERSITY OF LIFE

  2. Overview: Carbon—The Backbone of Life • Aside from water, the most biologically important molecules are carbon-based (organic). • Although cells are 70–95% water, the rest consists 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

  3. Concept 4.1: Organic chemistry is the study of carbon compounds A. Organic chemistry is the study of compounds that contain carbon 1. Organic compounds range from simple molecules to colossal ones 2. Most organic compounds contain hydrogen atoms in addition to carbon atoms

  4. 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

  5. A. The Formation of Bonds With Carbon 1. Carbon atom • Atomic number 6 (6 protons, 6 electrons, 6 neutrons) • 4 valance electrons • Forms 4 covalent bonds usually with H, O, N, C • Can form large, complex molecules 2. Carbon Dioxide (OCO) • Source of carbon for all organic molecules found in organisms

  6. B. Molecular Diversity Arising from Carbon Skeleton Variation 1. Covalent bonds link carbon atoms together in long chains that form the skeletal framework for organic molecules. 2. Carbon skeletons may vary in: • Length • Shape (straight chain, branched, ring) • Number and location of double bonds • Other elements covalently bonded to available sites 3. Variation contributes to complexity and diversity of organic molecules

  7. 04_05CarbonSkeletons_A.html

  8. C. Hydrocarbons • Hydrocarbons are organic molecules consisting of only carbon and hydrogen • Many organic molecules, such as fats and fossil fuels, have hydrocarbon components • Hydrocarbons can undergo reactions that release a large amount of energy • Hydrocarbon chains are hydrophobic because C—C and C—H bonds are nonpolar.

  9. Hydrocarbon

  10. D. Isomers 1. Isomers are compounds with the same molecular formula but different structures and properties. 2. Three types of isomers: a. Structural Isomers • Have different covalent arrangements of their atoms • Number of possible isomers increases as C skeleton size increases • Ex: C5 H13—3 isomers C8 H18—18 isomers C20 H42—366,319 isomers • May differ in location of double bonds

  11. Structural Isomers

  12. b. Geometric isomers • Have the same covalent arrangements but differ in spatial arrangements • Result from the fact that double bonds will not allow the atoms they join to rotate freely about the axis of the bonds • Subtle differences between isomers affects their biological activity

  13. Geometric Isomers

  14. c. Enantiomers • Are isomers that are mirror images of each other • Can occur when 4 different atoms or groups of atoms are bonded to the same carbon (asymmetric carbon) • Usually one form is biologically active and its mirror image is not • Important in the pharmaceutical industry • Two enantiomers of a drug may have different effects 04_07Isomers_A.html

  15. Enantiomers

  16. Enantiomer 04_07L_Dopa_A.html

  17. Concept 4.3: A small number of chemical groups are key to the functioning of biological molecules • Distinctive properties of organic molecules depend not only on the carbon skeleton but also on the molecular components attached to it • A number of characteristic groups are often attached to skeletons of organic molecules

  18. A. The Chemical Groups Most Important in the Process of Life 1. Functional groupsare the components of organic molecules that are most commonly involved in chemical reactions 2. The number and arrangement of functional groups give each molecule its unique properties 3. Functional group replaces an H bonded to the carbon of a hydrocarbon

  19. 4. The seven functional groups that are most important in the chemistry of life: • Hydroxyl group • Carbonyl group • Carboxyl group • Amino group • Sulfhydryl group • Phosphate group • Methyl group

  20. 5. The Seven Functional Groups a. Hydroxyl Group (-OH) • Consists of a hydrogen atom bonded to an oxygen atom, which is bonded to carbon H H | | H—C—C—OH R—OH | | H H Ethanol   • Polar group, therefore it makes the molecule attached to water soluble • Organic compounds with hydroxyl groups are called alcohols • Names end in –ol

  21. b. Carbonyl Group (-CO) • Consists of a carbon atom double-bonded to oxygen • Polar group, therefore it makes the molecule attached to water soluble • Found in sugars • If the carbonyl group is on the end of the carbon skeleton, the compound is an aldehyde OH OHO O | | // // H—C—C—C R—C | | \ \ H HHH Glyceraldehyde

  22. If the carbonyl group is in the internal part of a carbon skeleton, the compound is a ketone H O H O | || | || H—C—C—C—H R—C—R | | H H Acetone

  23. c. Carboxyl Group (-COOH) • Consists of a carbon atom which is both double-bonded to an oxygen and single bonded to the oxygen of a hydroxyl group • Polar group and water soluble • Have acidic properties • Compounds with this group are called carboxylic acids (organic acids) H OO | // // H—C—C R—C | \ \ H OH OH Acetic Acid

  24. d. Amino Group (-NH2) • Consists of a nitrogen atom bonded to two hydrogens and to the carbon skeleton • Polar group and water soluble • Weak base • Organic compounds with this functional group are called amines H HH | / / H—C—N R—N | \ \ H HH

  25. B. Amino Acids • Contain both carboxyl and amino groups HHO \ | // N—C—C / | \ H R OH aminocarboxyl

  26. e. Sulfhydryl Group (-SH) • Consists of an atom of sulfur bonded to an atom of hydrogen • Helps stabilize the structure of proteins • Organic compounds with this functional group are called thiols H H | | H—C—C—SH R—SH | | H H

  27. f. Phosphate Group (H3PO4) • Functional group which is the dissociated form of phosphoric acid • Polar group and water soluble • Acid properties • Form organic phosphates • Organic phosphates are important in cellular energy storage and transfer (ATP) OH OH H OO | | | || || H—C—C—C—O—P—O- R—O—P—O- | | | | | H HHO- O-

  28. ATP

  29. g. Methyl Group (-CH3) • Consists of a carbon bonded to 3 hydrogens • May be attached to a carbon or to a different atom • Not really a functional group because they are not reactive but may serve as important markers on organic molecules • Can affect expression of genes H / —C—H \ H

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