Question 1

The correct statement(s) regarding sugars is(are) Given: Specific rotations of L-(-)-glucose and L-(+)-fructose are -52.5^ and +92.5^ , respectively.

Accepted Answer

Statement (A) is incorrect: Nitric acid ( HNO _3) is a strong oxidizing agent that oxidizes both glucose and gluconic acid to saccharic acid. Statement (B) is correct: Fehling's reagent provides an alkaline medium. Under these conditions, fructose (a ketose) undergoes the Lobry de Bruyn-van Ekenstein rearrangement to form an equilibrium mixture of fructose, glucose, and mannose. Glucose and mannose are aldohexoses that readily reduce Fehling's solution, giving a positive test. Statement (C) is c

Question 2

In the following reaction sequence, major products X and Y are acyclic monomers. 500 mol of X completely reacts with 500 mol of Y to give 1 mol of a single biodegradable acyclic copolymer Z as the onl

Accepted Answer

Step 1: Identification of monomer X The given reaction sequence for X is: CH _3 I KCN CH _3 CN CH _3 CN H _3 O ^+, CH _3 COOH CH _3 COOH Red P, Br _2 BrCH _2 COOH (Hell-Volhard-Zelinsky reaction) BrCH _2 COOH NH _3 (excess) H _2 N - CH _2- COOH Thus, X is Glycine. Molar mass of X ( C _2 H _5 NO _2) = 2(12) + 5(1) + 14 + 2(16) = 75 g/mol . Step 2: Identification of monomer Y Caprolactam on acidic hydrolysis gives -aminocaproic acid: Caprolactam H _3 O ^+, H _2 N -( CH _2)_5- COOH Thus, Y is -amin

Question 3

A linear octasaccharide (molar mass =1024 ~g ~mol ^ -1 ) on complete hydrolysis produces three monosaccharides: ribose, 2-deoxyribose and glucose. The amount of 2-deoxyribose formed is 58.26 \%( w / w

Accepted Answer

M . M .=1024 Octasaccharide + M . M .=126 7 H _2 O aligned & Ribose + 2deoxyribose + glucose \ & Total mass =1024+126=1150 aligned aligned & 58.26= 134 n 1150 100 \ & 66.999 100 =134 n n=4.99=5 aligned 5 units of 2-Deoxyribose 1150=(5 150)+( x 150)+( y 180) aligned & 1150= 750 _ 5 unit + 150 x _ 300 + 180 y _ 180 \ & 2 unit 1 unit aligned n = 2.00

Question 4

For a double strand DNA, one strand is given below: The amount of energy required to split the double strand DNA into two single strands is _______ kcal mol ^ -1 . [Given: Average energy per H -bond f

Accepted Answer

A = T 2 H -bond G C 3 H -bond Number of A = T pair =7 Number of G C pair =6 Number of H-bond involve in A = T =7 2=14 Number of H -bond involve in G C =6 3=18 Energy required for A = T =14 1=14 Energy required for G C =18 1.5=27 Total energy required 14+27=41

Question 5

A disaccharide X cannot be oxidised by bromine water. The acid hydrolysis of X leads to a laevorotatory solution. The disaccharide X is

Accepted Answer

A and D cannot be oxidised by bromine water as they do not have hemiacetal linkage. The acid hydrolysis of A leads to a laevorotatory solution. A is sucrose which is dextrorotatory, on acid hydrolysis gives mixture of &#945; -D-glucopyranose and &#946; -D-fructofuranose, the mixture is laevorotatory.

Question 6

Treatment of D -glucose with aqueous NaOH results in a mixture of monosaccharides, which are

Accepted Answer

When glucose is treated with dilute NaOH, it gives a mixture of D-glucose, D-mannose and D-fructose. This reaction is known as Lobry de Bruyn-van Ekenstein rearrangement. Basic catalysed tautomerism through enediol intermediate takes place.

Question 7

Given: The compound  s ,  which on reaction with HNO 3 will give the product having degree of rotation,  &#945; D = &#8722; 52 .7 &#176;  is (are)

Accepted Answer

Now the structure, that shows [ ]_ D =-52.7^ is

Question 8

The structure of a peptide is given below. If the absolute values of the net charge of the peptide at pH = 2 , pH = 6 , and pH = 11 are z 1 , z 2 , and z 3 , respectively, then what is z 1 + z 2 + z 3

Accepted Answer

The structure of tripeptide will be as followed at PH = 2 (in highly acidic medium) hence z 1 = 2 at pH = 6 (in approximately neutral solution it will be Hence z 2 = 0 pH = 11 (in highly basic medium) the structure will be Hence z 3 will be 3 . Therefore z 1 + z 2 + z 3 = 2 + 0 + 3 = 5 .

Question 9

Which of the following statement(s) is(are) true?

Accepted Answer

→ Glucose → [ 0 ] Br 2 -H 2 O Glycolic acid → ∝ - Δ - Glucose and β - D Glucose → Hydrolysis of sucrose given dextrorotatory glucose and levorotatory fructose, → Monosaccharide cannot be hydrolyzed to give polyhydroxy aldehyde and ketones.

Biomolecules — Previous Year Questions & Solutions