Biomolecules Mock Test – Class 12 Chemistry

1. Assertion: Starch and cellulose give glucose on complete hydrolysis but show different digestibility in humans.
Reason: Starch contains mainly -glycosidic linkages, whereas cellulose contains glycosidic linkages that human digestive enzymes cannot efficiently hydrolyse.

2. A single linear polynucleotide chain contains nucleotide residues. The combined number of --glycosidic bonds and phosphodiester bonds in the intact chain is . Nine phosphodiester bonds are then hydrolysed. Find the original nucleotide count and the number of phosphodiester bonds remaining.

3. Glycogen differs from amylopectin mainly because glycogen:

4. The condition that enables fructose to reduce Tollens or Fehling reagent is mainly:

5. A short carbohydrate chain contains four monosaccharide units joined by condensation. The whole chain and each incorporated monosaccharide unit are best described, respectively, as:

6. Match each structural feature in Column I with its suitable protein-structure description in Column II.

7. Match the number of independent stereogenic centres in Column I with the corresponding maximum stereoisomer count in Column II, assuming no symmetry reduction.

8. The equation representing mild oxidation of glucose to gluconic acid is:

9. Consider the following claims.
Statement I: A non-reducing sugar must contain no oxygen atoms.
Statement II: Some RNA molecules can act as catalysts.
Statement III: Excessive intake of some fat-soluble vitamins may cause accumulation-related toxicity.
Statement IV: Hormones regulate cells by changing equilibrium constants through direct catalytic action.
The acceptable statements are:

10. A patient has normal digestive-enzyme production and adequate vitamin intake, but a gland releases too little of a blood-borne messenger that normally binds receptors on distant tissues. Which conclusion is most appropriate?

11. Assertion: Complementary base pairing enables a nucleic-acid strand to guide formation of another strand with a related sequence.
Reason: Each base shows selective pairing with a suitable complementary base.

12. Glucose, fructose and mannose form the same osazone mainly because:

13. Read the situation below and answer the question.
A globular enzyme is heated briefly. Its amino-acid sequence remains unchanged, and analysis shows no release of free amino acids. However, several -helical regions unfold, the active-site residues no longer have their original spatial arrangement and catalytic activity is lost.
The best interpretation is:

14. Match each glycogen feature in Column I with its suitable consequence in Column II.

15. The row in which the disaccharide, constituent monosaccharides, glycosidic linkage and reducing behaviour are all correctly stated is:

16. A standard B-DNA molecule contains approximately complete helical turns. Use base pairs per turn and rise per base pair. What are its approximate axial length and total nucleotide count?

17. Assertion: A denatured enzyme may retain its amino-acid sequence but lose catalytic activity.
Reason: Disruption of higher structure can alter the shape and chemical environment of its active site.

18. D-Glucose and D-mannose are related as:

19. An open-chain monosaccharide has six carbon atoms and its carbonyl group is located at . It is classified as:

20. A mixture contains nucleotide units. DNA nucleotides constitute of the mixture and belong to double-stranded DNA in which adenine forms of the DNA nucleotides. The remaining units are single-stranded RNA nucleotides with . What is the sum of the total hydrogen bonds in the DNA portion and the number of -hydroxyl groups in the RNA portion?

21. The open-chain structure contains:

22. A graph of specific rotation against time is recorded after pure -D-glucose is dissolved in water. The curve starts at a high positive value, decreases gradually and reaches a constant plateau. The plateau represents:

23. Assertion: The open-chain structural framework of glucose can have a maximum of stereoisomers.
Reason: Open-chain glucose contains only three independent stereogenic centres.

24. The cyclic form produced by interaction of the hydroxyl group with the aldehyde group of glucose is called glucopyranose because it contains:

25. Sample P contains nucleotides, of which are ribonucleotides and contain purines. Sample Q contains nucleotides, of which are ribonucleotides and contain purines. After mixing P and Q, determine the total moles of -hydroxyl groups and nitrogenous rings.

26. Consider the following statements about maltose.
Statement I: It contains an glycosidic linkage.
Statement II: It is a reducing disaccharide.
Statement III: Both anomeric carbons are involved in the glycosidic bond.
The acceptable statements are:

27. A sample contains glucose, vitamin C, glycine and starch. The macromolecule in this set is:

28. Classify the monosaccharide represented by :

29. Evaluate the following statements about -pleated sheets.
Statement I: Their backbone segments may be parallel or antiparallel.
Statement II: Their side chains commonly alternate above and below the sheet.
Statement III: They are stabilised only by covalent peptide bonds between neighbouring strands.
The acceptable statements are:

30. A vitamin deficiency lowers the activity of several enzymes even though the enzyme proteins are still being synthesised normally. A suitable explanation is that the vitamin:

31. For a linear carbohydrate containing monosaccharide residues, the number of water molecules required for complete hydrolysis is:

32. A molecule contains one tetrahedral carbon bonded to four different substituents and has no internal symmetry that removes chirality. Pure mirror-image forms of this molecule are expected to:

33. Maltose shows both mutarotation and reducing behaviour, whereas sucrose shows neither. The common structural reason for this difference is that maltose:

34. Evaluate the following statements.
Statement I: Formation of a glycosidic bond is a condensation process.
Statement II: Hydrolysis of a glycosidic bond consumes water.
Statement III: Every molecule containing a glycosidic bond is necessarily non-reducing.
The acceptable statements are:

35. Reduction of the carbonyl group of glucose produces:

36. A patient has megaloblastic anaemia caused by inadequate availability of a cobalt-containing vitamin. The deficient vitamin is:

37. In the hydrolysis of a peptide bond, water provides:

38. Two stereoisomeric sugars that differ in configuration at exactly one stereogenic carbon are called:

39. Three biomolecules are described below.
Molecule P is a polymer whose sequence stores hereditary information.
Molecule Q is a small non-polymeric substance that assists biochemical regulation.
Molecule R is a polymer of amino-acid residues and may act as a catalyst.
The identities of P, Q and R, respectively, are:

40. Ribose and glucose are placed in different carbon-number classes because:

41. Excessive long-term intake is more likely to cause accumulation-related toxicity for fat-soluble vitamins because they:

42. A nucleotide is formed from:

43. The open-chain structure most suitable for D-fructose is:

44. Vitamin A is most directly associated with:

45. Lactose yields on complete hydrolysis:

46. A single linear cellulose chain contains glucose residues. Complete hydrolysis of every glycosidic linkage in this chain consumes:

47. Assertion: For one connected acyclic glycogen molecule containing glucose residues, branching does not change the total glycosidic-linkage count from .
Reason: Changing an connection into an branch connection changes the linkage type but not the number of connections required to join residues in one acyclic molecule.

48. The correctly completed comparison is:

49. A patient has severely impaired absorption of dietary fats. The vitamins whose absorption is most directly at risk are:

50. Four unknown biological substances give the observations below.

The correct identification is: