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BIOMOLECULES, , , , > Carbohydrates - Classification (aldoses and ketoses), monosaccahrides (glucose and fructose), D-L, configuration, , > Proteins -Elementary idea of - amino acids, peptide bond, polypeptides, proteins, structure of proteins primary, secondary, tertiary structure and quaternary structures (qualitative idea only), denaturation of, proteins., , > Nucleic Acids: DNA and RNA, , , , STAND ALONE MCQs Ten eet, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Q. 1. Which of the following pairsrepresents anomers? ©) youl noon, (A) CHO CHO, H HO HO H 4 On He HO, HO HHO H HO eb aT e OH, H OH H OH a OH | HO HA, A OH H OH H i, CH,OH CH,OH CH,OH CH,OH g, (6) CHO CHO Ans. Option (C) is correct., H OH HO H Explanation: The isomers, which differ only in, HO: H H OH the configuration of the hydroxyl group at C-1,, are called anomers and are referred to as o and, H OH HO H efor., H OH HO HL, Q.2. Three cyclic structures of monosaccharides are, CELOH CHLOH given below which of these are anomers ?, © H OH| HO: H () H——OH) i) HO——H, H OH| H OH H—— OH Hon, HO H OHO HO HO4—HO yo 1-H O, H OH| HO: ‘OH H—— OH HoH, H H H #, , , , , , , , , , CH;0H CH,0H CH,0H CH,0H

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(ii) HO-—H, HO——H, HO—+—H 0, , H—t+—OH, HH, Ht, , CH,OH, , (A) (i) and (ii), , (B) Gi) and (ii), , (©) (and (iii), , (D) (iii) is anomer of (i) and (ii) ol, Ans. Option (A) is correct., , Explanation: Cyclic structures of monosaccharides, which differ in structure al carbon-1 are known, , , , , , , , , , , , as anomers., H—,;— 0H Hi H, H—— OH OH, , HO, OH, , Hp Oey, -— OH T, , , , , , , , , , CHOH, , CH,OH, ) a, Structure (1) and (Il) differ in structure at C-1., Q.3. Which of the following is an example of aldohexase?, , (A) Ribose, (C) Sucrose, Ans. Option (D) is correct., , (B) Fructose, (D) Glucose Al, , Explanation: Glucose is an example of aldohexose, because it contains an aldehyde group., , Q. 4. Glucose and fructose are:, , (A) isomers of each other, , (B) Homologous of each other, , (©) anomers of each other, , (D) enantiomers of each other {Al, Ans. Option (A) is correct., , Explanation: Glucose and _ fructose differ, structurally and stereochemically. They have, same molecular formula ie. C,H,,O,. Hence,, these are isomers of each other., , Q.5. Amino acids are:, (A) Acidic, (©) Amphoteric, , , , (B) Basic, , (D) Neutral, (R] [CBSE Delhi Set-I 2020], Ans. Option (C) is correct., , Explanation: Amino acids are amphoteric because, they contain both basic NH, group and acidic, -COOH group., , Q. 6. Which one is the complementary base of cytosine, , in one strand to that in other strand of DNA?, (A) Adenine (B) Guanine, (C) Thymine (D) Uracil, (U [CBSE O.D. Set-I1I 2020], Ans. Option (B) is correct., , Explanation: Guanine (G) is the complementary, base of cytosine (C) in one stand to that in other, stand of DNA., , csc, , Q.7. Curdling of milk is an example of:, , (A) breaking of peptide linkage, , (B) hydrolysis of lactose, , (©) breaking of protein into amino acids, , (D) denaturation of protein, , IICBSE, SQP 2020-21], , Ans. Option (D) is correct., , Explanation: Curdling, of milk is an example of, denaturation of milk proteins., , Q.8.Dinucleotide is obtained by joining two, nucleotides together by phosphodiester linkage., Between which carbon atoms of pentose sugars of, nucleotides are these linkages present ?, , (A) 5’ and 3’ (B) Vand 5’, (©) 5’ and 5’ (D) 3 and 3°, , Ans. Option (A) is correct., , Explanation: These linkages are present between, 5’ and 3’ of pentose sugars of nucleotides., , Q.9. Proteins are found to have two different types of, secondary structures, viz, a-helix and f-pleated, sheet structure. o-helix structure of protein is, stabilised by:, (A) Peptide bonds, (B) van der Waals forces, (C) Hydrogen bonds, (D) Dipole-dipole interactions Ul, , Ans. Option (C) is correct., , , , Explanation: o-helix structure of protein is, stabilised by hydrogen bonds. A polypeptide, chain forms all possible hydrogen bonds by, twisting into right-handed helix with the -NH, group of each amino acid residue hydrogen, bonded to >C=0 of an adjacent turn of helix., , Q.10. Lysine, H,N-(CH,),— GEECOOH is, , NH,, (A) G-Amino acid., (B) Basic amino acid., (C) Amino acid synthesised in body., (D) B-Amino acid., ‘Ans. Option (A), (B) and (C) is correct., Explanation: Lysine whose structure formula is, written as:, (i) It is an amino acid., (ii) It is basic amino acid because number of, NII, groups (2) is greater than number of, COOH group., (iii) It is non-essential amino acid because it is, synthesized in our body.

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ASSERTION AND REASON BASED MCQs, , [1 Mark each], , , , Directions: In the following questions, A statement, of Assertion (A) is followed by a statement of, Reason (R). Mark the correct choice as., , (A) Both Aand Rare true and Ris the correct explanation, ofA, , (B) Both A and R are true but R is NOT the correct, explanation of A, (C) Ais true but R is false, (D) Ais false and Ris True, Q.1. Assertion (A): D(+)-Glucose is dextrorotatory in, nature., Reason (R):‘D’ represents its dextrorotatory nature., Ans. Option (C) is correct., , Explanation: D' corresponds to the position of, — OH group on the right side on the farthest, asymmetric C-atom., , Q.2. Assertion (A):, carbohydrate., Reason (R): Carbohydrates are optically active, , polyhydroxy aldehyde or polyhydroxy ketone, or substances which give aldehyde or ketone on, , Deoxyribose, CHO, is not a, , hydrolysis., , Ans. Option (D) is correct., Explanation: Deoxyribose, CsHyQ, is a, carbohydrate and is the sugar moiety of DNA., , ©, BS, , . Assertion (A): Glucose reacts with hydroxylamine, to form an oxime and also adds a molecule of hydrogen cyanide to give cyanohydrin., , Reason (R): The carbonyl group is present in the, openchain structure of glucose., , CASE-BASED MCQs, , , , L, , Read the passage given below and answer the, following questions:, , EVIDENCE FOR THE FIBROUS NATURE OF DNA, , The basic chemical formula of DNA is now well, established. As shown in Figure 1 it consists of a, very long chain, the backbone of which is made up, of alternate sugar and phosphate groups, joined, togetherin regular’ 5’ phosphate di-ester linkages., ‘To each sugar is attached a nitrogenous base, only, four different kinds of which are commonly found, in DNA. Two of these-—adenine and guanine--are purines, and the other two thymine and, cytosine-are pyrimidines. A fifth base, 5-methyl, cytosine, occurs in smaller amounts in certain, organisms, and a sixth, 5-hydroxy-methyl-cytosine,, is found instead of cytosine in the T even phages., It should be noted that the chain is unbranched,, a consequence of the regular internucleotide, linkage. On the other hand the sequence of the, different nucleotides is, as far as can be ascertained,, , Ans. Option (A) is correct., , Explanation: Glucose reacts with hydroxylamine, to form an oxime and also adds a molecule of, hydrogen cyanide to give cyanohydrin which, confirms the presence of the carbonyl group in, the open chain structure of glucose., , Q.4. Assertion (A): The two strands of DNA are, complementary to each other, Reason (R): The hydrogen bonds are formed, between specific pairs of bases. [CBSE SQP 2020-21], Ans. Option (A) is correct., , Explanation: The two strands of DNA are, complementary to each other and hydrogen, bonds are formed between specific pairs of bases., , Q.5. Assertion (A); All naturally occurring a amino, acids except glycine are optically active., Reason (R): Most naturally occurring @ amino acids, have L-configuration., , Ans. Option (B) is correct., , Explanation: Most of the naturally occurring, amino acids have | —configuration. All naturally, occurring a—amino acids are optically active, except glycine., Q. 6. Assertion (A): Glycine must be taken through diet., Reason (R): It is non-essential amino acid., Ans. Option (D) is correct., , Explanation: Glycine must not be taken through, diet because it can be synthesized in our body, and a non-essential amino acid., , , , completely irregular. Thus, DNA has some features, which are regular, and some which are irregular., A similar conception of the DNA molecule as a, long thin fiber is obtained from physicochemical, analysis involving sedimentation, _ diffusion,, light scattering, and viscosity measurements., These techniques indicate that DNA is a very, asymmetrical structure approximately 20 A wide, and many thousands of angstroms long. Estimates, of its molecular weight currently center between, 5X" and X"™ (approximately 3 X™ nucleotides)., Surprisingly each of these measurements tend to, suggest that the DNA is relatively rigid, a puzzling, finding in view of the large number of single bonds, © per nucleotide) in the phosphate-sugar back, bone. Recently these indirect inferences have been, confirmed by electron microscopy. [CBSE-QB 2021], , Q. 1. Purines present in DNA are:, (A) adenine and thymine, (B) guanine and thymine, (©) cytosine and thymine, (D) adenine and guanine

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Ans. Option (D) is correct., , Explanation; Adenine and guanine are associated, ta form the adenine-thymine and guaninecytosine base pairs., , Q.2.DNA molecule has, linkage and, nucleotides, (A) regular, regular, (B) regular, irregular, (C) irregular, regular, (D) irregular, irregular, , Ans. Option (B) is correct., , Explanation; DNA molecule has regular, internucleotide linkage and irregular sequence, of the different nucleotides, , Q.3. DNA has a backbone, (A) phosphate-purine, (B) pyrimidines-sugar, (C) phosphate-sugar, (D) purine-pyrimidine, Ans. Option (C) is correct., , __ internucleotide, Sequence of the different, , Explanation: the backbone of DNA is made up of, Deoxyribose (Sugar) molecule connected to each, other using Phosphates., , Q. 4. Out of the four different kinds of nitrogenous bases, which are commonly found in DNA,, has been replaced in some organisms., (A) adenine (B) guanine, (©) cytosine (D) thymine, Ans. Option (C) is correct., , Explanation: A chemical compound that is used, to make one of the building blocks of DNA and, RNA. It is a type of pyrimidine. ie., cytosine., , IL. Read the passage given below and answer the, following questions:, The two monosaccharides are joined together by an, oxide linkage formed by the loss of awater molecule., Such a linkage between two monosaccharide, units through oxygen atom is called glycosidic, linkage. In disaccharides, if the reducing groups of, monosaccharides ie., aldehydic or ketonic groups, are bonded, these are non-reducing, sugars, e.g,, sucrose. On the other hand, sugars in which these, functional groups are free, are called reducing,, sugars, for example, maltose and lactose., Anon reducing disaccharide ‘’ on hydrolysis with, dilute acid gives an equimolar mixture of D-(+)glucose and D-(-)-Fructose., , A+H,O , ” CoH pOg+ CoH,, [o]p = +66.5° = +52.5° -92.4°, , Q.1. In the above reaction, reactant ‘N’is, (A) Glucose (B) Sucrose, , (C) Maltose (D) Fructose, Ans. Option (B) is correct., Explanation:, C,H,,0,,+H,O—* +C,H,,0,+ C,H,.0,, (A) Glucose Fructose, (Sucrose), , Q.2. What is the mixture of D-(+) glucose and D-(+), fructose known as ?, , (A) Anomers, (C) Invert sugar, Ans. Option (C) is correct., , Explanation: The mixture of D-(+)- glucose and, D-(-)-Fructose is known as invert sugar., , Q.3. Name the linkage that holds the two units in the, disaccharide ?, (A) Nucleoside linkage, (C) Peptide linkage, Ans. Option (B) is correct., , Explanation: The linkage which holds the two, monosaccharide units through oxygen alom is, , called glycosidic linkage., , Q.4. Glucose on reaction with acetic acid gives glucose, pentaacetate. What does it suggest about the, structure of glucose ?, , (A) C-lis anomeric carbon, , (B) C-5is anomeric carbon, , (C) 3¥-OH groups are present, , (D) 5’-OH groups are present, Ans. Option (D) is correct., , (B) Racemic mixture, (D) Optical mixture, , (B) Glycosidic linkage, (D) None of the above, , , , Explanation: Il indicales thal 5'-OH groups are, present which react with acetic acid to give, glucose pentaacetate., OR, , Proteins are found to have two different types of, secondary structures, viz. a-helix and p-pleated, sheet structure. o-helix structure of protein is, stabilised by, (A) Peptide bonds, (B) van der Waals forces, (C) Hydrogen bonds, (D) Dipole-dipole interactions, , Ans. Option (C) is correct., , Explanation: o-helix structure of protein is, stabilised by hydrogen bonds. A polypeptide, chain forms all possible hydrogen bonds b, twisting into right-handed helix with the -NH, group of each amino acid residue hydrogen, bonded to >C=O of an adjacent turn of helix., III. Read the passage given below and answer the, following questions:, The sequence of bases in m-RNA are read in a serial, order in groups of three at a time. Each triplet of, nucleotides (having, a specific sequence of bases) is, known as codon. Lach codon specifies one amino, acid. Many amino acids have more than one, codons. The amino acids are brought to the mRNA, by another type of RNA and called t3NA. Each, amino acid has atleast one corresponding tRNA., At one end of the tRNA molecule is a trinucleotide, base sequence that is complementary to some, trinucleotide base sequence on mRNA., Q.1.Which of the following nitrogen bases is not, present in RNA?, (A) Thymine, (C) Guanine, Ans. Option (A) is correct., , (B) Adenine, (D) Cytosine, , Explanation: In RNA, thymine is not present. In, place of thymine, uracil is present in RNA.

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Q. 2. Each triplet of nucleotides is called:, , (A) Anticodon (B) Codon, (C) mRNA (D) RNA, Ans. Option (B) is correct., Explanation: Each triplet of nucleotides,, , which have a specific sequence of bases, is called, codon., , Q.3. Each codon specifies:, (A) Lamino acid, (©) 3 amino acids, Ans. Option (A) is correct., , (B) 2 amino acids, (D) None of these, , Explanation: Each codon specifies one amino, acid. Many amino acids possess more than one, , codons., Q.4. In mRNA, the complementary bases of AAT is:, (A) CCG (B) UUA, (©) AUU (D) UU, , Ans. Option (B) is correct., , Explanation: In mRNA, , , , So, the complementary bases of AAT in mRNA is, , UUA., OR, The amino acids are brought to the mRNA by:, (A) rRNA (B) DNA, (C) tRNA (D) None of these, , Ans. Option (C) is correct., , Explanation: The amino acids are brought to the, mRNA by tRNA (transfer RNA)., , IV Read the passage given below and answer the, following questions:, Adenosine triphosphate (ATP) is the energycarrying, molecule found in the cells of all living, things. ATP captures chemical energy obtained, from the breakdown of food molecules and, releases it to fuel other cellular processes. ATP is a, nucleotide that consists of three main structures:, the nitrogenous base, adenine; the sugar, ribose;, and a chain of three phosphate groups bound, to ribose. The phosphate tail of ATP is the actual, power source which the cell taps. Available energy, is contained in the bonds between the phosphates, and is released when they are broken, which, occurs through the addition of a water molecule (a, process called hydrolysis). Usually only the outer, phosphate is removed from ATP to yield energy;, when this occurs ATP is converted to adenosine, diphosphate (ADP), the form of the nucleotide, having only two phosphates., The imporlance of ATP (adenosine triphosphate), as the main source of chemical energy in living, matter and its involvement in cellular processes, has long been recognized. ‘The primary mechanism, whereby higher organisms, including humans,, generate AIP is through mitochondrial oxidative, phosphorylation. For the majority of organs,, the main metabolic fuel is glucose, which in, the presence of oxygen undergoes complete, combustion to CO, and H,0:, , CgHy,0, + 60, > 60, 4+ 6H,O + energy, , ‘The free energy (AG) liberated in this exergonic (AG, , is negative) reaction is partially trapped as ATP in, two consecutive processes: glycolysis (cytosol) and, oxidative phosphorylation (mitochondria). The, first produces 2 mol of ATP per mol of glucose,, and the second 36 mol of ATP per mol of glucose., Thus, oxidative phosphorylation yields 17-[8 times, as much useful energy in the form of ATP as can, be obtained from the same amount of glucose by, glycolysis alone., The efficiency of glucose metabolism is the ratio of, amount of energy produced when | mol of glucose, oxidised in cell to the enthalpy of combustion of, glucose. The energy lost in the process is in the, form of heat. This heat is responsible for keeping, us warm. [CBSE-QB 2021], The following questions are multiple choice, questions. Choose the most appropriate answer:, , Q. 1. Cellular oxidation of glucose is a:, , (A) spontaneous and endothermic process, (B) non spontaneous and exothermic process, (C) non spontaneous and endothermic process, (D) spontaneous and exothermic process, Ans. Option (D) is correct., Q. 2. What is the efficiency of glucose metabolism if 1, , mole of glucose gives 38ATP energy? (Given: The, enthalpy of combustion of glucose is 686 kcal, ATP, , = 7.3kcal), (A) 100% (B) 38%, (C) 62% (D) 80%, , Ans. Option (B) is correct., , Explanation: Glucose catabolism yields a Total of, 38 ATP. 38 ATP x 7.3 kcal/mol ATP = 262 kcal., Glucose has 686 kcal. Thus the efficiency of, glucose metabolism is 262/686 x 100 = 38%., , Q. 3. Which of the following statement is true?, (A) ATP is a nucleoside made up of nitrogenous, base adenine and ribose sugar., (B) ATP consists the nitrogenous base, adenine, and the sugar, deoxyribose., (C) ATP is a nucleotide which contains a chain of, three phosphate groups bound to ribose sugar., (D) The nitrogenous base of ATP is the actual, power source., Ans. Option (C) is correct., , Q.4. Nearly 95% of the energy released during cellular, respiration is due to:, (A) glycolysis occurring in cytosol, (B) oxidative phosphorylation occurring in cytosol, (C) glycolysis in occurring mitochondria, (D) oxidative phosphorylation occurring — in, , mitochondria, Ans. Option (D) is correct., , Q. 4. Which of the following statements is correct:, , (A) ATP is a nucleotide which has three phosphate, groups while ADP is a nucleoside which three, phosphate groups., , (B) ADP contains a nitrogenous bases adenine,, ribose sugar and two phosphate groups bound, to ribose., , (C) ADP is the main source of chemical energy in, living matter., , (D) ATP and ADP are nucleosides which differ in, number of phosphate groups., , Ans. Option (B) is correct.