MCQ on Carbohydrates Part-2

Biochemistry MCQ-2: A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, with the empirical formula C(H2O)n. This is the Part-2 of the MCQ series on Carbohydrates. You may also like: MCQ on Carbohydrates Part-1  |  Part-3  |

1.  The vitreous humor of eye is composed of_______.
a.       Heparin
b.      Hyaluronic acid

c.       Keratan Sulfate
d.      Chondroitin sulfate

2. N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM) in peptidoglycan is connected by ____glycosidic linkage.
a.       α 1 – 4
b.      β 1 – 4

c.       α 1 – 2
d.      β 1 – 2

3.  Sulbactam is a ________.
a.       β-lactam antibiotic
b.      β lactamase

c.       β lactamase inhibitor
d.      A class of penicillin

Note on Carbohydrates  |  Monosacchrides  |  Disaccharides  |  Polysaccharides  |  Sugar Derivates  |  Glycosaminoglycans  | Glycoconjugates  |

4.  Which of the following is not a sugar molecule of the O-antigen of gram negative bacteria?
a.       Tyvelose
b.      Abequose

c.       2 keto-3-deoxyoctanoate
d.      Teichoic acid

5.  Glycosidic bond between galactose and glucose in lactose is____.
a.       α 1 – 4
b.      β 1 – 4

c.       α 1 – 2
d.      β 1 – 2

6. Which of the following is a sugar alcohol?
a.       Arabitol
b.      Manitol

c.       Sorbitol
d.      All of these

7.  Minimum number of carbons required for an aldose sugar to have a cyclic structure is___.
a.       3
b.      4

c.       5
d.      6

8.  The reserve food materials of Rhodophyceae (red algae) is ______.
a.       Laminarin
b.      Chrysolaminarin

c.       Floridian starch
d.      Starch

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9.  Reserve food material of fungi is____.
a.       Glucose
b.      Starch

c.       Laminarin
d.      Glycogen

10.  Glycosidic bond in Trehalose is _____.
a.       α 1 – 4
b.      α 1 – 2

c.       α 1 – 1
d.      β 1 – 2

11.  Which of the following is a non-reducing sugar?

a.       Maltose
b.      Lactose

c.       Trehalose
d.      Cellobiose

12.  A disaccharide of galactose and fructose joined by β 1 – 4 glycosidic linkage:

a.       Trehalose
b.      Lactulose

c.       Gentiobiose
d.      Melibiose

13.  Which of the following sugar do not form cyclic structure?

a.       Erythrulose
b.      Dihydroxyacetone

c.       Both (a) and (b)
d.      Erythrose

14.  A disaccharide of two glucose molecules joined by β 1 – 6 glycosidic linkage:

a.       Trehalose
b.      Gentiobiose

c.       Lactulose
d.      Melibiose

15.  Glycerol moieties in Teichoic acid of bacterial cell wall are linked each other by _____.

a.       Ether bonds
b.      Ester bonds

c.       Phosphodiester bonds
d.      Glycosidic bonds

16.  A disaccharide of galactose and glucose in α 1 – 6 glycosidic linkage:

a.       Lactose
b.      Melibiose

c.       Gentiobiose
d.      Verbascose

17.  Which of the following sequence correctly represent the sweetness of Glucose, Sucrose and Fructose

a.       Glucose < Sucrose < Fructose
b.      Sucrose < Glucose < Fructose

c.       Glucose ≤ Sucrose < Fructose
d.      Glucose > Fructose > Sucrose

18.  After the osazone test, the sample sugar gave needle shaped crystals, the sample sugar will be _____.

a.       Glucose
b.      Fructose

c.       Maltose
d.      Cellulose

19.  Partial fermentation of cane sugar by Leuconostoc mesenteroides produce:

a.       Glucose and Fructose
b.      Glucose and Gluconic acid

c.       Fructose and Gluconic acid
d.      Dextran

20.  Which of the following commonly acts as the precursor for the synthesis of Vitamin C (Ascorbic acid) in plants:

a.       Fructose
b.      Ribose

c.       Glucose
d.      Ribulose

You may also like: MCQ on Carbohydrates Part-1  |  Part-3  |

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Answers with explanations:

1. Ans. (b). Hyaluronic acid

Heparin, hyaluronic acid, keratan Sulfate and chondroitin sulfate are glycosaminoglycan, commonly called as mucopolysaccharides or GAGs. They are the main heteropolysaccharides of extracellular matrix (ECM). They are linear polymers of repeating disaccharide units. One of the monosaccharides of the disaccharide unit is always either N-acetylglucosamine or N-acetylgalactosamine. The other monosaccharide unit in most cases will be uronic acid. GAGs are heavily sulfated and the sulfate group holds fixed negative charges. This negative charge imparts the overall negative charge of extracellular surface of the cells.

Hyaluronic acid is the most abundant glycosaminoglycan. They form clear and highly viscous solutions and thus they are present in the vitreous humor of eye. They are also present in the lubricants of synovial fluids of the joints. They are essential components of the cartilage.

Heparin: An anticoagulant, which is a highly sulfated glycosaminoglycan. Heparin is considered as the highest negative charge holding biological molecule.

2. Ans. (b). β 1 – 4

3. Ans. (c). β-lactamase inhibitor

β-lactam antibiotics: an antibiotic class with β-lactam ring. Example: Penicillin, Ampicillin and Cephalosporin.

β-lactamases: A class of enzyme produced by some bacteria to degrade β-lactam antibiotics and there by impart resistance against it.

β-lactamase inhibitor: They inhibit β-lactamase enzyme.  They are injected with β-lactam antibiotics to overcome antibiotic resistance in bacteria that secret β-lactamase inhibitor. Clavulanic acid and Sulbactam are important β-lactamase inhibitors.

4. Ans. (d). Teichoic acid

O-antigens, better known as Lipopolysaccharides (LPS) or endotoxins, are glyco-conjugates of the outer membrane of gram negative bacteria. They are so called because they elicit strong immune response in animals. Tyvelose, Abequose and 2- keto-3-deoxyoctanoate are important O-antigens.

Teichoic acid (TA): they are bacterial polysaccharides found in the cell wall of gram-negative bacteria. They are composed of glycerol phosphate linked via phosphodiester bonds.

Liptoteichoic acid (LTA) is cell wall component of gram positive bacteria.

5. Ans. (b). β 1 – 4

6. Ans. (d). All of these

7. Ans. (b). 4

A ketose sugar with 5 or more carbons only forms cyclic structure.

8. Ans. (c). Floridian starch

Laminarin: Food reserve of brown algae

Chrysolaminarin: food reserve of diatoms (Bacillariophyceae)

Starch: Food reserve of green algae and higher plants

9. Ans. (d). Glycogen

10. Ans. (c). α 1 – 1

Trehalose (= mycose or tremalose) is a disaccharide of two glucose residues linked by α-1 – 4 glycosidic linkage. Similar to sucrose, it is a non-reducing sugar since its anomeric carbon atoms are involved in glycosidic linkage. Trehalose has good water holding capacity. It is a major energy storage molecule used by insects for flight. This is because the hydrolysis of trehalose yields two glucose molecules at a time which is considered as more efficient than the hydrolysis of starch where only one glucose is produced.

11. Ans. (c). Trehalose

Maltose, lactose and cellobiose are reducing disaccharides since at least one anomeric carbon is free in either of their monosaccharide residues.

12. Ans. (b). Lactulose

Lactulose is a non-digestable disaccharide of galactose and fructose linked by β -1 – 4 glycosidic linkage. Since it is not digested by the enzyme system in human, lactulose is used as an osmotic laxative (laxative = agents that loses stools and increase bowel movements) for the treatment of chronic constipation.

13. Ans. (c). Both (a) and (b).

Erythrulose (4C) and Dihydroxyacetone (3C) are ketose sugars. Ketose sugars having less than five carbons do not form cyclic structure.

Erythrose is an aldo-tetrose, an aldo sugar with four or more carbon can form cyclic structures in the aqueous medium.

14. Ans. (b). Gentiobiose

Crocin (a carotenoid) that gives the colour of saffron is a diester of gentiobiose and a dicarboxylic acid crocetin.

Melibiose: a reducing disaccharide of galactose and glucose linked by α- 1 – 6 glycosidic linkage.

15. Ans. (c). Phosphodiester bonds

16. Ans. (b). Melibiose

Verbascose: A pentasaccharide of three galactose, glucose and fructose (galactose-galactose-galactose-glucose-fructose)

17. Ans. (a). Glucose < Sucrose < Fructose

Monosaccharides are sweet in taste however different monosaccharide varies in their sweetness. Sweetness chart of carbohydrates are constructed with glucose as the reference.

 sweetness of different carbohydrates

18. Ans. (a). Glucose

Osazones are derivatives of carbohydrates, formed when sugar molecules are reacted with phenylhydrazine. Sugar molecules can be differentiated based on the pattern or shape of respective osazones. Osazone test was developed by Emil Fischer to study the stereochemistry of monosaccharides.

Monosaccharides form needle shaped or broomstick shaped crystals

Disaccharides form sunflower shaped crystals

Lacto-osazone: A tuft (or tight balls) of needle shaped crystals

Malto-osazone: Broad needle shaped crystals

19. Ans. (d). Dextran

Dextran is a complex branched homopolysaccharide of glucose molecules. Structurally they are α- 1 – 6 lined glucose residues with α-1 – 3 branches. Dextran is considered as one of the strongest biomolecules. The dental plaques are rich in dextran

Sephadex, a matrix used in size exclusion chromatography, is the trade name of cross linked dextran molecules.

20. Ans. (c). Glucose


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