Chapter 16 Carbohydrates JA edit PDF

Preview

Summary

Chapter 16: Carbohydrates Which of the following statements concerning carbohydrates is INCORRECT? A) Carbohydrates serve important energy and structural roles for plants and animals. B) Monosaccharides are the simplest carbohydrates and are known as simple sugars. C) Monosaccharides join together t...

Description

Chapter 16: Carbohydrates 1. Which of the following statements concerning carbohydrates is INCORRECT? A) Carbohydrates serve important energy and structural roles for plants and animals. B) Monosaccharides are the simplest carbohydrates and are known as simple sugars. C) Monosaccharides join together to form disaccharides and polysaccharides by hydrogen bonding. D) Humans store excess glucose for short term energy requirements in the polysaccharide glycogen. E) Carbohydrates that can be oxidized by the Benedict’s reagent are known as reducing sugars. Ans: C 2. Monosaccharides are structurally defined as which of the following? A) polyhydroxy aldehydes or polyhydroxyketones B) hemiacetals and acetals C) polyamides or polyesters D) enols and enolates E) carboxylic acids Ans: A 3. Carbohydrates are chiral or “handed” biomolecules. What does the term chiral describe? A) a molecule that has a mirror image B) a molecule that can be superimposed on its mirror image C) a molecule that exists in two nonsuperimposable mirror image forms D) a molecule that can be digested by the body E) a molecule that may be synthesized by the body Ans: C 4. Which enantiomer of glyceraldehyde is represented in the following structure?

A) L-glyceraldehyde B) -glyceraldehyde C) -glyceraldehyde D) D-glyceraldehyde E) It is impossible to determine from the structure alone. Ans: A

Page 161

Chapter 16 Carbohydrates

5. Which of the following statements concerning stereochemistry is INCORRECT? A) Stereoisomers are molecules with the same molecular formula, same bonding pattern, but different spatial arrangement of atoms. B) A chiral carbon is a carbon atom that has four different groups bonded to it. C) A molecule that contains a chiral carbon is a chiral molecule, and exists as a pair of enantiomers. D) Enantiomers are superimposable mirror image stereoisomers. E) A racemic mixture of enantiomers is optically inactive. Ans: D 6. Propranol is a chiral compound that exists as a pair of enantiomers. One enantiomer is used to treat irregular heartbeats, and the other is used as a contraceptive. Which labeled carbon atom(s) is/are chiral?

A) C-1 B) C-2 C) C-3 D) C-4 E) C-1 and C-3 Ans: C 7. How does the structure of -D-glucose differ from that of -D-glucose? A) -D-Glucose is an aldose and -D-glucose is a ketose. B) In -D-glucose the −OH group on the last chiral carbon is on the left, and in -Dglucose the –OH group on the last chiral carbon is on the right. C) In -D-glucose the −OH group on the hemiacetal carbon is below the ring, and in D-glucose the –OH group on the hemiacetal carbon is above the ring. D) In -D-glucose the last –CH2OH group is on the right, and in -D-glucose the −CH2OH group is on the left. E) There is no structural difference between the two. Ans: C 8. Which carbohydrate is present in RNA? A) ribulose B) glucose C) mannose D) ribose E) fructose Ans: D

Page 162

Chapter 16 Carbohydrates

9. The open chain structure of D-fructose is shown. What is the Haworth projection for D-fructose?

A)

B)

C)

D)

E) Ans: E

Page 163

Chapter 16 Carbohydrates

10. What product is formed when the monosaccharide below is oxidized by a basic solution of Benedict's reagent?

A)

B)

C)

D)

E) Ans: E 11. The simplest aldose is named 2,3-dihydroxypropanal, although it is more commonly referred to as glyceraldehyde. What is the structure of glyceraldehyde?

A)

B)

Page 164

Chapter 16 Carbohydrates

C)

D) E) Ans: D

Page 165

Chapter 16 Carbohydrates

12. A ketose can be converted to an aldose through an enediol intermediate. What is the structure of the enediol intermediate when D-fructose is converted to D-glucose?

A)

B)

C)

D)

Page 166

Chapter 16 Carbohydrates

E) Ans: B 13. What is a reducing sugar? A) a carbohydrate that can be oxidized by Benedict’s reagent B) a sugar that contains an acetal C) a carbohydrate that can be reduced by Benedict’s reagent D) a sugar that can be digested by the body E) a carbohydrate that is part of a polysaccharide Ans: A 14. What term is used to describe an excess of glucose in a urine sample? A) glucosamine B) glucosemia C) glucosuria D) hypoglucose E) glucagon Ans: C 15. What test can be used to distinguish between a reducing sugar and a nonreducing sugar? A) iodine test B) Tollens’ test C) chromic acid test D) Benedict’s test E) hydrolysis test Ans: D 16. What disaccharide is composed of two glucose units joined together? A) lactose B) maltose C) sucrose D) cellulose E) galactose Ans: B

Page 167

Chapter 16 Carbohydrates

17. What two monosaccharides join to form the disaccharide lactose? A) glucose and galactose B) galactose and fructose C) ribose and galactose D) glucose and fructose E) glucose and glucose Ans: A 18. What two monosaccharides combine to form sucrose? A) glucose and galactose B) galactose and fructose C) ribose and galactose D) glucose and fructose E) ribose and fructose Ans: D 19. Starch is composed of which two polysaccharides? A) chitin and chondroitin B) glycogen and cellulose C) amylose and amylopectin D) glucosamine and glycogen E) cellulose and galactosamine Ans: C 20. Amylose and amylopectin are both components of starch. How do their structures differ? A) Amylose is a monosaccharide and amylopectin is a polysaccharide. B) Amylose is a polysaccharide and amylopectin is a disaccharide. C) Amylose is an aldose and amylopectin is a ketose. D) Amylose is a linear polysaccharide and amylopectin is a branched polysaccharide. E) Amylose is a hexose and amylopectin is a pentose. Ans: D 21. What are the major sites of glycogen storage in the human body? A) fat and pancreas B) liver and muscle C) stomach and intestines D) kidneys and stomach E) heart and brain Ans: B

Page 168

Chapter 16 Carbohydrates

22. Why are humans not able to digest cellulose? A) Humans lack the enzyme cellulase which is required to hydrolyze the (14) glycosidic bonds present in cellulose. B) Humans lack the enzyme lactase which is required to hydrolyze the lactose produced from the digestion of cellulose into glucose and galactose. C) Humans lack the enzyme lactase which is required to convert the galactose produced from the digestion of cellulose into glucose. D) Cellulose is not naturally available to humans. E) None of the above; humans actually can readily digest cellulose. Ans: A 23. What is the most abundant carbohydrate on Earth? A) sucrose B) cellulose C) glycogen D) fructose E) amylose Ans: B 24. How do the structures of amylose and cellulose differ? A) Amylose is a linear polysaccharide and cellulose is a branched polysaccharide. B) Amylose is a homopolysaccharide and cellulose is a heteropolysaccharide. C) Amylose is a polysaccharide of glucose units, and cellulose is a polysaccharide of galactose units. D) Amylose is a polysaccharide made up of D-glucose units, and cellulose is a polysaccharide made up of L-glucose units. E) Amylose contains (14) glycosidic bonds joining D-glucose units, and cellulose contains (14) glycosidic bonds joining D-glucose units. Ans: E

Page 169

Chapter 16 Carbohydrates

25. The monosaccharide derivative shown below bonds to hydrophobic molecules in the liver. What effect does this have on the molecule to which it binds?

A) It increases the hydrophobicity of the molecule, making it more soluble in fatty tissues. B) It increases the polarity of the molecule, making it more soluble in bodily fluids, and more readily removed. C) It eliminates the ability of the molecule to act as a nutritional source of energy. D) It decreases the polarity of the hydrophobic molecule, allowing it to be retained in the body longer. E) It increases the nutritional value of the molecule by allowing it to be retained by the body longer. Ans: B 26. What is the simplest type of carbohydrate? A) sugars B) monosaccharides C) cellulose Ans: B

D) E)

starch None of the choices are correct.

27. What complex carbohydrate provides a source of dietary fiber? A) starch B) cellulose C) lactose D) sucrose E) glucose Ans: B 28. What two functional groups are present in all monosaccharides? A) hydroxyl and carboxyl D) amino and hydroxyl B) alkene and phosphate E) hydroxyl and carbonyl C) acid and carbonyl Ans: E 29. What term describes a carbon atom that has four different groups bonded to it? A) chiral D) meso B) unbalanced E) unsaturated C) trigonal pyramidal Ans: A 30. What is the stereochemical relationship between your right and left hands? A) cis- and trans- isomers D) enantiomers B) structural isomers E) diastereomers C) conformers Ans: D

Page 170

Chapter 16 Carbohydrates

31. Which monosaccharide found in the blood has its concentration regulated by the hormones insulin and glucagon? A) fructose B) glucose C) galactose D) ribose E) sucrose Ans: B 32. To what class of carbonyl containing compounds does glucose belong? A) aldehyde B) ketone C) alcohol D) amide E) Both A and B are correct. Ans: A 33. What type of compound is produced in the reaction between an alcohol and an aldehyde? A) diol D) hemiacetal B) carboxylic acid E) ester C) acetal Ans: D 34. The structure of ribose, found in RNA, is shown below. How does the structure of deoxyribose, found in DNA, compare to it?

A) B) C) D) E) Ans:

Deoxyribose has one less oxygen. Deoxyribose has one more oxygen. Deoxyribose has one less oxygen and one less hydrogen. Deoxyribose has one less hydrogen. Deoxyribose has one less oxygen and two less hydrogens. A

35. Disaccharides and polysaccharides contain monosaccharide units joined together by which of the following? A) dipole/dipole forces D) glycosidic linkages B) hydrogen bonding E) peptide bonds C) hemiacetal bonds Ans: D 36. Which property of D-glyceraldehyde and L-glyceraldehyde differs? A) melting point B) solubility C) direction of rotation of plane-polarized light D) density E) None of the choices are correct. Ans: C

Page 171

Chapter 16 Carbohydrates

37. The Fischer projections of two monosaccharides are shown below. What is the relationship between the two monosaccharides?

A) enantiomers B) diastereomers C) structural isomers D) meso isomers E) cis-trans isomers Ans: B 38. What term describes carbohydrates consisting of two to ten monosaccharide units bonded together? A) disaccharide D) glycogen B) polysaccharide E) starch C) oligosaccharide Ans: C 39. Monosaccharides exist predominantly as cyclic hemiacetals. Cyclic hemiacetals have both an  and a  form. Which of the following monosaccharides are shown in the  form?

A) III only B) IV only C) I and III D) II and IV E) All are shown in the  form. Ans: A

Page 172

Chapter 16 Carbohydrates

40. The Fischer projection for the monosaccharide ribulose is shown below. How may this monosaccharide be appropriately classified?

A) ketotetrose B) ketopentose C) aldotriose D) aldopentose E) ketotriose Ans: B 41. What term properly describes the relationship between the two compounds shown?

A) betamers B) constitutional isomers C) enantiomers D) anomers E) unrelated Ans: D 42. Which enantiomer of glyceraldehyde is represented in the following structure?

A) trans Ans: E

B) 

C) 

D) D

E) L

43. What is the molecular formula of glucose? A) C6H12O5 B) C6H12O6 C) C6H10O5 D) C5H10O5 Ans: B 44. What is the name of the simplest ketose? A) acetone B) fructose C) ethanone Ans: D

Page 173

D) E)

E) C9H18O9

1,3-dihydroxyacetone ethose

Chapter 16 Carbohydrates

45. What is the position of the -OH group on carbon-1 in the Haworth projection of -Dglucose? A) above the ring B) below the ring C) in the plane of the ring D) to the left of carbon-1 E) to the right of carbon-1 Ans: A 46. Which form of D-glucose has the -OH group on carbon-1 below the ring in the Haworth projection? A) meso B) L C)  D)  E)  Ans: C 47. The Fischer projection for the naturally occurring form of fucose, one of the carbohydrates used as a cell marker in the determination of blood types, is shown below. Is this D-fucose or L-fucose?

A) D-fucose B) L-fucose C) It is neither D- nor L-; fucose is not chiral. D) It is impossible to determine from the Fischer projection alone. Ans: B 48. What type of product forms in the intramolecular reaction between the aldehyde portion of the glucose molecule below and its C-5 hydroxyl group?

A) B) C) Ans:

disaccharide carboxylic acid hemiacetal C

D) E)

ester stereoisomer

49. In which blood type do the red blood cells carry no antigens? A) A B) B C) AB D) O E) Both A and B are correct. Ans: D

Page 174

Chapter 16 Carbohydrates

50. What monosaccharide combines with glucose to form the disaccharide lactose? A) glucose B) mannose C) fructose D) sucrose E) galactose Ans: E 51. What is the principal carbohydrate found in milk? A) glucose B) maltose C) mannose D) lactose E) sucrose Ans: D 52. Which of the following is a nonreducing disaccharide? A) mannose B) maltose C) sucrose D) lactose E) ribose Ans: C 53. Which of the following carbohydrates is also known as dextrose, and is the sugar referred to when blood sugar is measured? A) glycogen B) sucrose C) glucose D) starch E) lactose Ans: C 54. Which of the following is a highly branched polymer of glucose? A) dextran B) cellulose C) amylose D) amylopectin E) peptidoglycan Ans: D 55. What polysaccharide found in animals has a structure very similar to amylopectin? A) glucose B) glycogen C) starch D) amylose E) cellulose Ans: B

Page 175

Chapter 16 Carbohydrates

56. Melibiose is a carbohydrate found in some plant juices. Which of the following statements concerning melibiose is INCORRECT?

A) It is a disaccharide. B) It is composed of two different monosaccharide units. C) It contains both an acetal and a hemiacetal. D) It contains an (15) glycosidic linkage. E) It is a reducing sugar. Ans: D

Page 176

Chapter 16 Carbohydrates

57. Gentobiose, a rare disaccharide found in saffron, produces two identical monosaccharides when it undergoes hydrolysis. What is the structure of the monosaccharide hydrolysis product?

A)

B)

C)

D) E) None of the above. Ans: A 58. Which of the following carbohydrates cannot be digested by humans? A) glycogen B) cellulose C) amylose D) amylopectin E) sucrose Ans: B 59. What type of glycosidic linkage between glucose units is present in cellulose? A) (14) D) (16) B) (14) E) a mixture of (14) and (16) C) (16) Ans: B

Page 177

Chapter 16 Carbohydrates

60. What heteropolysaccharide is a component of cartilage and may relieve symptoms of osteoarthritis? A) chondroitin sulfate D) glycogen B) hyaluronic acid E) -D-glucuronate C) heparin Ans: A 61. Which of the following is NOT a carbohydrate? A) sucrose B) simple sugar C) fatty acid D) cellulose E) starch Ans: C 62. Which of the following correctly matches the term with its definition? A) ketose – monosaccharide with a ketone functional group B) aldose – monosaccharide with a carbonyl group on the end carbon C) tetrose – has the formula (CH2O)n where n = 4 D) pentose – a five carbon sugar E) All of the choices are correct. Ans: E 63. Which statement concerning a chiral carbon is correct? A) A chiral carbon has four different groups bonded to it. B) A chiral carbon has a hydroxyl group and carbonyl group bonded to it. C) A chiral carbon has two double bonds connected to it. D) A chiral carbon always causes plane-polarized light to rotate in a clockwise fashion. E) A chiral carbon is present in all aldehydes. Ans: A 64. Which statement is FALSE? A) Molecules that contain a chiral carbon will rotate plane-polarized light. B) If one molecule rotates plane-polarized light clockwise 10°, its enantiomer will rotate plane-polarized light counterclockwise by 10°. C) The D- and L- designation of sugars is determined by the chiral atom farthest from the most oxidized carbon. D) All sugars designated with a D- prefix will rotate plane-polarized light in a clockwise direction. E) Dextrorotatory sugars rotate plane-polarized light clockwise and are designated by a plus sign (+). Ans: D

Page 178

Chapter 16 Carbohydrates

65. For D-glyceraldehyde shown below, which carbon, if any, is chiral? H

1 C

O

2 H

C

OH

3 CH 2OH

A) B) C) Ans:

C-1 C-2 C-3 B

D) E)

C-2 and C-3 None of the carbon atoms are chiral.

66. Which of the following is NOT a common name for D-glucose? A) table sugar D) blood sugar B) dextrose E) All of the choices are correct. C) grape sugar Ans: A 67. Aldaric acids are a type of monosaccharide derivative, formed when both the aldehyde group and the terminal –CH2OH group of a monosaccharide are oxidized to carboxylic acids. D-Glucaric acid is the aldaric acid derivative of D-glucose. What is the structure of D-glucaric acid?

A) I B) II C) III D) IV E) V Ans: B

Page 179

Chapter 16 Carbohydrates

68. Which of the following is NOT a term that would properly describe glucose as it is shown below?

A) monosaccharide B) aldose C) hemiacetal D) D-sugar E) reducing sugar Ans: C 69. Which of the following is the major storage molecule of glucose in animals? A) cellulose B) sucrose C) blood sugar D) amylose E) glycogen Ans: E 70. Enantiomers are always mirror images of each other. Ans: True 71. The molecular formula of deoxyribose is C5H10O4. Ans: True 72. All monosaccharides give a positive result with Benedict's reagent. Ans: True 73. The glycosidic linkage found in most carbohydrates is an acetal bond. Ans: True 74. The principal carbohydrate in milk is galactose. Ans: False 75. If left untreated, galactosemia leads to mental retardation. Ans: True 76. Cellulose molecules are all unbranched, while starch contains only branched molecules. Ans: False 77. Humans can digest glucose polymers containing (14) glycosidic linkages, but not those with (14) linkages. Ans: True

Page 180

Chapter 16 Carbohydrates

78. A termite's digestive organs produce a cellulase that allows it to break down wood fibers. Ans: False 79. If D-glucose is levorotatory, then L-glucose must be levorotatory as well. Ans: False

Page 181...