Chapter 4 Carbon and the Molecular Diversity of Life All organisms are composed mostly of chemical structures based on the element carbon. This chapter builds upon information and concepts introduced in Chapters 2 and 3 and extends the descriptions and analysis to more detailed consideration of the carbon atom. Of all the elements, carbon is unparalleled in its ability to form molecules that are large, complex, and diverse. Student understanding of this complexity and diversity is aided by naming and describing typical groups of atoms (functional groups) that are mixed and matched to construct larger carbon-based molecules. Much of the material in this chapter lends itself to questions that emphasize recall and application; and many such questions are presented. But other topics in this chapter require synthesis and interpretation, as well as visualization of three-dimensional arrangements of atoms, and so we have added several questions that will be more challenging for most students. This chapter lays the foundation for later elaboration of roles of molecular structure in various life processes. Several form/function questions assess student understanding of these concepts. Multiple-Choice Questions 1) Organic chemistry is a science based on the study of A) functional groups. B) vital forces interacting with matter. C) carbon compounds. D) water and its interaction with other kinds of molecules. E) inorganic compounds. Topic: Concept 4.1 2) Early 19th-century scientists believed that living organisms differed from nonliving things as a result of possessing a ʺlife forceʺ that could create organic molecules from inorganic matter. The term given to this belief is A) organic synthesis. B) vitalism. C) mechanism. D) organic evolution. E) inorganic synthesis. Topic: Concept 4.1 61
3) The experimental approach taken in current biological investigations presumes that A) simple organic compounds can be synthesized in the laboratory from inorganic precursors, but complex organic compounds like carbohydrates and proteins can only be synthesized by living organisms. B) a life force ultimately controls the activities of living organisms and this life force cannot be studied by physical or chemical methods. C) although a life force, or vitalism, exists in living organisms, this life force cannot be studied by physical or chemical methods. D) living organisms are composed of the same elements present in nonliving things, plus a few special trace elements found only in living organisms or their products. E) living organisms can be understood in terms of the same physical and chemical laws that can be used to explain all natural phenomena. Answer: E Topic: Concept 4.1 4) One of the following people set up a closed system to mimic Earthʹs early atmosphere and discharged electrical sparks through it. A variety of organic compounds common in organisms were formed. Who did this? A) Stanley Miller B) Jakob Berzelius C) Friedrich Wohler D) Hermann Kolbe E) August Kekulé Topic: Concept 4.1 62 Chapter 4, Carbon and the Molecular Diversity of Life
5) Which of the following people used this apparatus to study formation of organic compounds? A) Stanley Miller B) Jakob Berzelius C) Friedrich Wohler D) Hermann Kolbe E) August Kekulé Topic: Concept 4.1 6) Which of the following people was the first to synthesize an organic compound, urea, from inorganic starting materials? A) Stanley Miller B) Jakob Berzelius C) Friedrich Wohler D) Hermann Kolbe E) August Kekulé Topic: Concept 4.1 Chapter 4, Carbon and the Molecular Diversity of Life 63
7) Which of the following peopleʹs synthesis of this compound from inorganic starting materials provided evidence against vitalism? A) Stanley Miller B) Jakob Berzelius C) Friedrich Wohler D) Hermann Kolbe E) August Kekulé Topic: Concept 4.1 8) Which of the following people synthesized an organic compound, acetic acid, from inorganic substances that had been prepared directly from pure elements? A) Stanley Miller B) Jakob Berzelius C) Friedrich Wohler D) Hermann Kolbe E) August Kekulé Topic: Concept 4.1 9) Which of the following peopleʹs synthesis of this compound from inorganic starting materials provided evidence against vitalism? A) Stanley Miller B) Jakob Berzelius C) Friedrich Wohler D) Hermann Kolbe E) August Kekulé Topic: Concept 4.1 64 Chapter 4, Carbon and the Molecular Diversity of Life
10) One of the following people was the first to suggest that organic compounds, those found in living organisms, were distinctly different from inorganic compounds found in the nonliving world. Though this suggestion is now known to be incorrect, it stimulated important research into organic compounds. Who suggested this? A) Stanley Miller B) Jakob Berzelius C) Friedrich Wohler D) Hermann Kolbe E) August Kekulé Topic: Concept 4.1 11) How many electron pairs does carbon share in order to complete its valence shell? A) 1 B) 2 C) 3 D) 4 E) 8 12) A carbon atom is most likely to form what kind of bond(s) with other atoms? A) ionic B) hydrogen C) covalent D) A and B only E) A, B, and C 13) Which of the following statements best describes the carbon atoms present in all organic molecules? A) They were incorporated into organic molecules by plants. B) They were processed into sugars through photosynthesis. C) They are ultimately derived from carbon dioxide. D) Only A and C are correct. E) A, B, and C are correct. Answer: E Chapter 4, Carbon and the Molecular Diversity of Life 65
14) Why are hydrocarbons insoluble in water? A) The majority of their bonds are polar covalent carbon-to-hydrogen linkages. B) The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages. C) They are hydrophilic. D) They exhibit considerable molecular complexity and diversity. E) They are lighter than water. 15) How many structural isomers are possible for a substance having the molecular formula C4H10? A) 1 B) 2 C) 4 D) 3 E) 11 Skill: Application/Analysis Figure 4.1 16) The two molecules shown in Figure 4.1 are best described as A) optical isomers. B) radioactive isotopes. C) structural isomers. D) nonradioactive isotopes. E) geometric isomers. 66 Chapter 4, Carbon and the Molecular Diversity of Life
Figure 4.2 17) Shown here in Figure 4.2 are the structures of glucose and fructose. These two molecules differ in the A) number of carbon, hydrogen, and oxygen atoms. B) types of carbon, hydrogen, and oxygen atoms. C) arrangement of carbon, hydrogen, and oxygen atoms. D) number of oxygen atoms joined to carbon atoms by double covalent bonds. E) answers A, B, and C 18) Shown here in Figure 4.2 are the structures of glucose and fructose. These two molecules are A) geometric isotopes. B) enantiomers. C) geometric isomers. D) structural isomers. E) nonisotopic isomers. 19) Which of the following statements correctly describes geometric isomers? A) They have variations in arrangement around a double bond. B) They have an asymmetric carbon that makes them mirror images. C) They have the same chemical properties. D) They have different molecular formulas. E) Their atoms and bonds are arranged in different sequences. Chapter 4, Carbon and the Molecular Diversity of Life 67
Figure 4.3 20) The two molecules shown in Figure 4.3 are best described as A) enantiomers. B) radioactive isotopes. C) structural isomers. D) nonisotopic isomers. E) geometric isomers. Answer: E 21) Research indicates that Ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers; that is, molecules that A) have identical three-dimensional shapes. B) are mirror images of one another. C) lack an asymmetric carbon. D) differ in the location of their double bonds. E) differ in their electrical charge. 22) Research indicates that Albuterol, a drug used to relax bronchial muscles, improving airflow and thus offering relief from asthma, consists only of one enantiomer, the R-form. Why is it important for this drug to consist of only one enantiomeric form, rather than a mixture of enantiomers? A) Different enantiomers may have different or opposite physiological effects. B) It is impossible to synthesize mixtures of enantiomers. C) It is much less expensive to synthesize one enantiomer at a time. D) Albuterol is an example of a compound for which only one enantiomer exists. E) Only the R-form of Albuterol has been studied; until more information is available, physicians prefer to use the pure R-form. 68 Chapter 4, Carbon and the Molecular Diversity of Life
23) Three or four of the following illustrations depict different structural isomers of the organic compound with molecular formula C6H14. For clarity, only the carbon skeletons are shown; hydrogen atoms that would be attached to the carbons have been omitted. Which one, if any, is NOT a structural isomer of this compound? A) B) C) D) E) Each of the illustrations in the other answer choices depicts a structural isomer of the compound with molecular formula C6H14. Chapter 4, Carbon and the Molecular Diversity of Life 69
24) Which of the pairs of molecular structures shown below depict enantiomers (enantiomeric forms) of the same molecule? A) B) C) D) E) Skill: Synthesis/Evaluation 70 Chapter 4, Carbon and the Molecular Diversity of Life
25) Which of the pairs of molecular structures shown below do NOT depict enantiomers (enantiomeric forms) of the same molecule? A) B) C) D) E) Skill: Synthesis/Evaluation 26) Three or four of the pairs of structures shown below depict enantiomers (enantiomeric forms) of the same molecule. Which pair, if any, are NOT enantiomers of a single molecule? If each of the pairs depicts enantiomers, choose answer F. A) Chapter 4, Carbon and the Molecular Diversity of Life 71
B) C) D) E) F) Both illustrations in each of the other answer choices depict enantiomers of the same molecule. Skill: Synthesis/Evaluation 27) Thalidomide and L-dopa, shown below, are examples of pharmaceutical drugs that occur as enantiomers, or molecules that A) have identical three-dimensional shapes. B) are mirror images of one another. C) lack an asymmetric carbon. D) differ in the location of their double bonds. E) differ in their electrical charge. 72 Chapter 4, Carbon and the Molecular Diversity of Life
28) A compound contains hydroxyl groups as its predominant functional group. Which of the following statements is true concerning this compound? A) It lacks an asymmetric carbon, and it is probably a fat or lipid. B) It should dissolve in water. C) It should dissolve in a nonpolar solvent. D) It wonʹt form hydrogen bonds with water. E) It is hydrophobic. 29) Which is the best description of a carbonyl group? A) an oxygen joined to a carbon by a single covalent bond B) a nitrogen and two hydrogens joined to a carbon by covalent bonds C) a carbon joined to two hydrogens by single covalent bonds D) a sulfur and a hydrogen joined to a carbon by covalent bonds E) a carbon atom joined to an oxygen by a double covalent bond Answer: E Figure 4.4 30) What is the name of the functional group shown in Figure 4.4? A) carbonyl B) ketone C) aldehyde D) carboxyl E) hydroxyl 31) Which of the following contains nitrogen in addition to carbon, oxygen, and hydrogen? A) an alcohol such as ethanol B) a monosaccharide such as glucose C) a steroid such as testosterone D) an amino acid such as glycine E) a hydrocarbon such as benzene Chapter 4, Carbon and the Molecular Diversity of Life 73
32) Which of the following is a false statement concerning amino groups? A) They are basic in ph. B) They are found in amino acids. C) They contain nitrogen. D) They are nonpolar. E) They are components of urea. 33) Which two functional groups are always found in amino acids? A) ketone and aldehyde B) carbonyl and carboxyl C) carboxyl and amino D) phosphate and sulfhydryl E) hydroxyl and aldehyde 34) Amino acids are acids because they always possess which functional group? A) amino B) carbonyl C) carboxyl D) sulfhydryl E) aldehyde 35) A carbon skeleton is covalently bonded to both an amino group and a carboxyl group. When placed in water it A) would function only as an acid because of the carboxyl group. B) would function only as a base because of the amino group. C) would function as neither an acid nor a base. D) would function as both an acid and a base. E) is impossible to determine how it would function. Skill: Application/Analysis 36) A chemist wishes to make an organic molecule less acidic. Which of the following functional groups should be added to the molecule in order to do so? A) carboxyl B) sulfhydryl C) hydroxyl D) amino E) phosphate Skill: Application/Analysis 74 Chapter 4, Carbon and the Molecular Diversity of Life
37) Which functional groups can act as acids? A) amine and sulfhydryl B) carbonyl and carboxyl C) carboxyl and phosphate D) hydroxyl and aldehyde E) ketone and amino The following questions refer to the structures shown in Figure 4.5. Figure 4.5 38) Which of the structures is an impossible covalently bonded molecule? A) A B) B C) C D) D E) E 39) Which of the structures contain(s) a carboxyl functional group? A) A B) B C) C D) C and E E) none of the structures Answer: E Chapter 4, Carbon and the Molecular Diversity of Life 75
40) In which of the structures are the atoms bonded by ionic bonds? A) A B) B C) C D) C, D, and E only E) none of the structures Answer: E The following questions refer to the functional groups shown in Figure 4.6. 41) Which is a hydroxyl functional group? 42) Which is an amino functional group? 43) Which is a carbonyl functional group? Figure 4.6 44) Which is a functional group that helps stabilize proteins by forming covalent cross-links within or between protein molecules? Answer: E 45) Which is a carboxyl functional group? 76 Chapter 4, Carbon and the Molecular Diversity of Life
46) Which is an acidic functional group that can dissociate and release H+ into a solution? 47) Which is a basic functional group that can accept H+ and become positively charged? The following questions refer to the molecules shown in Figure 4.7. Figure 4.7 48) Which molecule is water soluble because it has a hydroxyl functional group? 49) Which molecule is an alcohol? 50) Which molecules contain a carbonyl group? A) A and B B) B and C C) C and D D) D and E E) E and A 51) Which molecule has a carbonyl functional group in the form of a ketone? Chapter 4, Carbon and the Molecular Diversity of Life 77
52) Which molecule has a carbonyl functional group in the form of an aldehyde? 53) Which molecule contains a carboxyl group? 54) Which molecule can increase the concentration of hydrogen ions in a solution and is therefore an organic acid? The following questions refer to the molecules shown in Figure 4.8. Figure 4.8 55) Which molecule contains a sulfhydryl functional group? 56) Which molecule functions to transfer energy between organic molecules? 57) Which molecule contains an amino functional group, but is not an amino acid? 58) Which molecule is a thiol? 78 Chapter 4, Carbon and the Molecular Diversity of Life
59) Which molecule is an organic phosphate? 60) Which molecule can function as a base? 61) Testosterone and estradiol are A) nucleic acids. B) carbohydrates. C) proteins. D) phospholipids. E) steroids. Answer: E 62) Testosterone and estradiol are male and female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other? A) Testosterone and estradiol are structural isomers but have the same molecular formula. B) Testosterone and estradiol are geometric isomers but have the same molecular formula. C) Testosterone and estradiol have different functional groups attached to the same carbon skeleton. D) Testosterone and estradiol have distinctly different chemical structures, with one including four fused rings of carbon atoms, while the other has three rings. E) Testosterone and estradiol are enantiomers of the same organic molecule. Chapter 4, Carbon and the Molecular Diversity of Life 79
Self-Quiz Questions The following questions are from the end-of-chapter-review Self-Quiz questions in Chapter 4 of the textbook. 1) Organic chemistry is currently defined as A) the study of compounds made only by living cells. B) the study of carbon compounds. C) the study of vital forces. D) the study of natural (as opposed to synthetic) compounds. E) the study of hydrocarbons. 2) Which of the following hydrocarbons has a double bond in its carbon skeleton? A) C3H8 B) C2H6 C) CH4 D) C2H4 E) C2H2 3) Choose the term that correctly describes the relationship between these two sugar molecules: A) structural isomers B) geometric isomers C) enantiomers D) isotopes 4) Identify the asymmetric carbon in this molecule: 80 Chapter 4, Carbon and the Molecular Diversity of Life
5) Which functional group is not present in this molecule? A) carboxyl B) sulfhydryl C) hydroxyl D) amino 6) Which action could produce a carbonyl group? A) the replacement of the OH of a carboxyl group with hydrogen B) the addition of a thiol to a hydroxyl C) the addition of a hydroxyl to a phosphate D) the replacement of the nitrogen of an amine with oxygen E) the addition of a sulfhydryl to a carboxyl 7) Which chemical group is most likely to be responsible for an organic molecule behaving as a base? A) hydroxyl B) carbonyl C) carboxyl D) amino E) phosphate Chapter 4, Carbon and the Molecular Diversity of Life 81