1. What happens in optical activity of sugars?

A. They conduct electricity in solution B. They rotate plane-polarized light either to the right or left due to chiral centers C. They change color when heated D. They form crystals when cooled

2. What does reaction with acetyl chloride (CH3COCl) indicate in sugars?

A. Presence of aldehyde group B. Presence of alcoholic hydroxyl groups capable of forming esters C. The sugar is a ketose D. The sugar contains amino groups

3. What mechanism is involved in mutarotation?

A. Oxidation of sugar B. Opening and reclosing of the hemiacetal ring forming the aldehyde intermediate C. Formation of peptide bonds D. Hydrolysis of glycosidic bonds

4. Which sugar does not occur free in nature but is found in glycoproteins?

A. D-Galactose B. D-Mannose C. D-Glucose D. D-Fructose

5. What structural difference exists between aldoses and ketoses?

A. Number of carbon atoms B. Aldehyde group in aldoses, ketone group in ketoses C. Presence of amino group D. Presence of phosphate group

6. What is the significance of osazone formation in sugar analysis?

A. It helps in sugar solubility determination B. It is used to prepare crystalline derivatives useful for identifying types of sugars based on melting points and crystal structure C. It changes the sugar’s optical activity D. It produces sugar acids

7. What is the anomeric carbon in cyclic sugars?

A. The carbon with a ketone group B. The carbon that was the carbonyl carbon before ring formation and becomes asymmetric after cyclization C. The last carbon in the chain D. The carbon bonded to only hydrogens

8. Which of the following are ketohexoses commonly found in fruits and sweeter than glucose?

A. D-Mannose B. D-Galactose C. D-Fructose D. D-Glucose

9. Which enzyme catalyzes the conversion of one epimer to another, such as the conversion of galactose to glucose in the liver?

A. Mutarotase B. Isomerase C. Epimerase D. Kinase

10. What kind of optical isomer rotates polarized light to the right?

A. Laevorotatory (–) B. Dextrorotatory (+) C. Racemic mixture D. Achiral compound

11. What defines carbohydrates chemically?

A. Hydrocarbons with a double bond B. Aldehyde or ketone derivatives of polyhydric alcohols C. Proteins composed of amino acids D. Lipids with glycerol backbone

12. What is an asymmetric carbon atom?

A. Carbon with a double bond B. Carbon bonded to four different atoms/groups C. Carbon with no attached hydrogen D. Carbon bonded to identical groups

13. What is the general empirical formula for most carbohydrates?

A. CnH2n-2On B. CnH2nOn C. CnHnOn D. CnH2n+1On

14. Which reaction indicates the presence of alcohol groups in sugars due to ester formation?

A. Iodination B. Acetylation C. Mutarotation D. Osazone formation

15. What is the general formula for most carbohydrates?

A. CnH2nOn B. CnHnO2n C. CnH2n+1On D. CnH2n-2On

16. What is “resolution” in the context of optical isomers?

A. The formation of racemic mixtures B. Separation of optically active isomers from racemic mixtures C. Mutation of sugars during metabolism D. Reaction with acids to form esters

17. How is D- or L-series determined in sugars?

A. By molecular weight B. By color reaction with iodine C. By orientation of the OH group on the carbon adjacent to the terminal primary alcohol (usually C-5) D. By solubility in water

18. Which sugar is an epimer of glucose differing at carbon-4?

A. D-Fructose B. D-Galactose C. D-Mannose D. D-Ribose

19. What is a racemic mixture in terms of optical activity?

A. A mixture where one isomer dominates and shows optical rotation B. A mixture of equal amounts of dextrorotatory and laevorotatory isomers that cancel each other’s activity C. A mixture that is optically active with a unique rotation sign D. A mixture with no asymmetric carbons

20. What does stereoisomerism in sugars result from?

A. Different molecular weights B. Presence of asymmetric carbon atoms leading to different spatial configurations C. Different chemical formulas D. Variations in the number of carbon atoms

21. Into which major groups are carbohydrates classified?

A. Monosaccharides and lipids B. Disaccharides and nucleic acids C. Monosaccharides, disaccharides, oligosaccharides, polysaccharides D. Only monosaccharides and polysaccharides

22. Which properties of osazones help in sugar identification?

A. Color and sweetness B. Melting points, crystal structures, and precipitation times C. Molecular weight and hydrolysis rate D. Solubility in water and alcohol

23. What type of groups in sugars enable formation of esters with organic and inorganic acids?

A. Aldehyde groups B. Keto groups C. Alcoholic –OH groups D. Amino groups

24. What kind of isomers are α-D-glucose and β-D-glucose?

A. Enantiomers B. Epimers C. Anomers D. Diastereomers

25. Which sugar is dextrorotatory and an epimer of glucose?

A. D-Mannose B. D-Galactose C. D-Fructose D. D-Ribose

26. How are carbohydrates subdivided based on carbon atoms?

A. Amino acids, fatty acids, nucleotides B. Trioses, tetroses, pentoses, hexoses C. Saturated and unsaturated D. Alkanes and alkenes

27. Which sugar acid is formed when an aldose is oxidized to yield a dibasic acid?

A. Aldonic acid B. Saccharic acid C. Uronic acid D. Fatty acid

28. What characterizes saccharic acids?

A. Monobasic acids with aldehyde groups B. Dibasic dicarboxylic acids formed by oxidation of both aldehyde and terminal hydroxyl group in aldoses C. Ketoses with modified hydroxyl groups D. Unmodified sugars

29. What is mutarotation?

A. Change in molecular weight during metabolism B. The change in optical rotation due to conversion between α and β forms of a sugar in solution C. Sugar oxidation in the body D. Formation of oligosaccharides from monosaccharides

30. Why are uronic acids considered reducing?

A. Because they contain free aldehyde groups after oxidation B. Because they can form esters C. Because they are insoluble in water D. Because they only occur in polysaccharides

31. What is the Lobry de Bruyn-Van Ekenstein reaction?

A. The formation of disaccharides from monosaccharides B. Interconversion of aldoses and ketoses by dilute alkali forming enediol intermediates C. Hydrolysis of polysaccharides D. Oxidation of sugars to acids

32. Which statement about monosaccharides is CORRECT?

A. They can be hydrolyzed into simpler sugars B. They contain only ketone groups C. They serve as both fuel molecules and building blocks for nucleic acids D. They have no hydroxyl groups

33. Which enzyme is required for conversion of galactose to glucose?

A. Glucosidase B. Epimerase C. Amylase D. Lipase

34. What occurs when glucose exists in α- or β-forms?

A. Different chemical formulas B. Different optical rotations due to the position of the hydroxyl group on the anomeric carbon C. Change in number of carbon atoms D. Formation of peptide bond

35. How can glucose, fructose, and mannose interconvert in solution?

A. By oxidation reactions B. In presence of strong acid C. Via an enediol intermediate under weak alkaline conditions such as Ba(OH)2 or Ca(OH)2 D. By enzyme-catalyzed hydrolysis

36. What happens when an aldose is heated with concentrated HI?

A. It forms sugar acids B. It forms iodo compounds by loss of oxygen C. It produces osazones D. It polymerizes

37. Which sugar is an epimer of glucose differing at the carbon-4 position?

A. D-Fructose B. D-Mannose C. D-Galactose D. D-Ribose

38. What is characteristic about D-fructose regarding rotation of plane-polarized light?

A. It is dextrorotatory (+) B. It is laevorotatory (–) C. It shows no optical activity D. It is racemic

39. Which sugar is a ketohexose commonly called fruit sugar?

A. D-Glucose B. D-Fructose C. D-Mannose D. D-Galactose

40. Which of the following statements about epimers is true?

A. Epimers differ at multiple stereocenters B. Epimers differ at only one stereocenter C. Epimers are mirror images D. Epimers are enantiomers

41. What chemical reaction is used primarily to prepare crystalline derivatives of sugars for their identification based on melting points and crystal structure?

A. Esterification B. Oxidation C. Osazone formation D. Reduction

42. What is the process called when an aldohexose’s optical rotation changes until reaching a constant value due to conversion between α and β forms?

A. Epimerization B. Mutarotation C. Racemization D. Resolution

43. What is epimerization in sugar chemistry?

A. Conversion of one epimer to another, facilitated by enzymes like epimerase B. Conversion of ketose to aldose C. Formation of polymers from monosaccharides D. Hydrolysis of disaccharides

44. What are aldonic acids?

A. Sugar acids formed by oxidation of the aldehyde group in aldoses B. Sugar acids formed by reduction of ketones C. Amino sugars D. Phosphorylated sugars

45. During iodocompound formation, heating an aldose with concentrated HI results in:

A. Formation of a sugar acid B. Conversion into a sugar alcohol C. Replacement of oxygen by iodine atoms forming a iodo compound D. Cleavage into smaller sugars

46. The interconversion of glucose, fructose, and mannose in weakly alkaline solutions occurs due to the formation of which intermediate?

A. Lactone B. Enediol C. Hemiacetal D. Hemiketal

47. When a beam of plane-polarized light is passed through a sugar solution and is rotated to the right, the sugar is called:

A. Laevorotatory B. Dextrorotatory C. Racemic D. Optically inactive

48. What are uronic acids in carbohydrate chemistry?

A. Monobasic acids formed by oxidation of terminal primary alcohol groups in sugars, retaining the aldehyde group B. Sugar ketones C. Amino sugars D. Phosphorylated sugars

49. What does the term “racemic” refer to in sugar chemistry?

A. A sugar molecule with no chiral centers B. A mixture of equal amounts of dextrorotatory and laevorotatory isomers with no net optical rotation C. Sugar with high sweetness D. Sugar with low solubility

50. Which carbon atom becomes asymmetric and is termed the anomeric carbon after sugar cyclization?

A. Carbon-2 B. Carbon-3 C. Carbon-1 D. Carbon-5