Carbohydrates & Nucleic Acids — NEET Biology MCQs with Solutions
Free NEET Biology Carbohydrates & Nucleic Acids MCQs with step-by-step solutions (126 questions). Part of Biomolecules. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Carbohydrates & Nucleic Acids · easy · theory
The most abundant carbohydrate (and organic macromolecule) in nature, forming plant cell walls, is:
A. Cellulose ✓ Correct
B. Chitin
C. Starch
D. Glycogen
Solution: Cellulose (a homopolymer of glucose) is the most abundant polysaccharide; it forms plant cell walls.
Q2 — Carbohydrates & Nucleic Acids · easy · theory
The nitrogenous bases in DNA are adenine, guanine, cytosine and:
A. Thymine ✓ Correct
B. Xanthine
C. Uracil
D. Hypoxanthine
Solution: DNA contains thymine; in RNA, uracil replaces thymine.
Q3 — Carbohydrates & Nucleic Acids · medium · theory
The bond joining monosaccharide units in a polysaccharide is a ______ bond:
A. Peptide
B. Phosphodiester
C. Glycosidic ✓ Correct
D. Ester
Solution: Glycosidic bonds link sugar residues; nucleotides are joined by phosphodiester bonds and amino acids by peptide bonds.
Q4 — Carbohydrates & Nucleic Acids · medium · theory
A nucleotide consists of a nitrogenous base + a ______ sugar + a phosphate group:
A. Tetrose
B. Hexose
C. Triose
D. Pentose ✓ Correct
Solution: Nucleotides contain a pentose (ribose in RNA, deoxyribose in DNA); base + sugar (without phosphate) is a nucleoside.
Q5 — Carbohydrates & Nucleic Acids · hard · theory
Purines and pyrimidines differ structurally in that purines (adenine, guanine) are:
A. Both contain phosphate
B. Both single-ringed
C. Single-ringed, pyrimidines double-ringed
D. Double-ringed, while pyrimidines are single-ringed ✓ Correct
Solution: Purines (A, G) have a fused double-ring; pyrimidines (C, T, U) have a single six-membered ring.
Q6 — Carbohydrates & Nucleic Acids · hard · theory
The linkage between the two strands of DNA is by ______ bonds between complementary bases (A=T, G≡C):
A. Hydrogen ✓ Correct
B. Phosphodiester
C. Peptide
D. Glycosidic
Solution: The two antiparallel strands are held by hydrogen bonds (2 between A–T, 3 between G–C); the backbone is joined by phosphodiester bonds.
Q7 — Carbohydrates & Nucleic Acids · easy · numerical
Which of the following is a monosaccharide?
A. Sucrose
B. Fructose ✓ Correct
C. Maltose
D. Starch
Solution: Fructose is a single sugar unit (monosaccharide); sucrose and maltose are disaccharides and starch is a polysaccharide.
Q8 — Carbohydrates & Nucleic Acids · easy · numerical
The disaccharide sucrose is made up of:
A. glucose and galactose
B. fructose and galactose
C. glucose and glucose
D. glucose and fructose ✓ Correct
Solution: Sucrose (table sugar) is formed by a glycosidic bond between glucose and fructose.
Q9 — Carbohydrates & Nucleic Acids · easy · numerical
A nucleoside consists of a nitrogenous base joined to a sugar, but it lacks:
A. the nitrogenous base
B. the pentose sugar
C. a hydroxyl group
D. a phosphate group ✓ Correct
Solution: A nucleoside is base + sugar; adding a phosphate group converts it into a nucleotide.
Q10 — Carbohydrates & Nucleic Acids · easy · numerical
Which of the following is a pyrimidine base?
A. Both adenine and guanine
B. Adenine
C. Guanine
D. Cytosine ✓ Correct
Solution: Cytosine (with thymine and uracil) is a single-ringed pyrimidine; adenine and guanine are double-ringed purines.
Q11 — Carbohydrates & Nucleic Acids · medium · numerical
Starch and cellulose are both glucose polymers, yet they differ because:
A. starch is made of fructose while cellulose is made of glucose
B. starch has α-glycosidic linkages forming a helix, while cellulose has β-glycosidic linkages forming straight chains ✓ Correct
C. cellulose is branched while starch is unbranched
D. starch contains nitrogen while cellulose does not
Solution: The α-1,4 linkages of starch allow a helical, coiled structure, whereas the β-1,4 linkages of cellulose give straight, unbranched fibres suited to structural support.
Q12 — Carbohydrates & Nucleic Acids · medium · numerical
Glycogen differs from amylose (a component of starch) mainly in that glycogen is:
A. a structural polysaccharide of plant cell walls
B. a polymer of fructose units
C. a straight, unbranched chain
D. highly branched ✓ Correct
Solution: Glycogen, the storage carbohydrate of animals and fungi, is a highly branched glucose polymer, unlike the largely unbranched amylose.
Q13 — Carbohydrates & Nucleic Acids · medium · numerical
Inulin, a storage carbohydrate present in some plants, is a polymer of:
A. galactose
B. glucose and fructose alternately
C. glucose
D. fructose ✓ Correct
Solution: Inulin is a fructan — a polymer built from fructose units.
Q14 — Carbohydrates & Nucleic Acids · medium · numerical
Chitin, the material of arthropod exoskeletons and fungal walls, is best described as a:
A. nitrogen-containing polysaccharide (a polymer of N-acetylglucosamine) ✓ Correct
B. lipid of the cell membrane
C. simple homopolymer of glucose only
D. protein made of amino acid subunits
Solution: Chitin is a complex (hetero)polysaccharide containing nitrogen, being a polymer of the amino-sugar N-acetylglucosamine.
Q15 — Carbohydrates & Nucleic Acids · medium · numerical
According to Chargaff's rule, in a double-stranded DNA molecule:
A. purines are always fewer than pyrimidines
B. the sum of adenine and guanine always equals two
C. the amount of adenine equals thymine and that of guanine equals cytosine ✓ Correct
D. the amount of adenine equals guanine
Solution: Chargaff's equivalence rule states A = T and G = C, so total purines equal total pyrimidines in duplex DNA.
Q16 — Carbohydrates & Nucleic Acids · medium · numerical
In a polynucleotide chain, successive nucleotides are linked by ______ bonds between the sugar of one nucleotide and the phosphate of the next:
A. phosphodiester ✓ Correct
B. hydrogen
C. peptide
D. glycosidic
Solution: The sugar-phosphate backbone of a nucleic acid is held together by phosphodiester bonds; hydrogen bonds instead join the two strands.
Q17 — Carbohydrates & Nucleic Acids · medium
Read the following statements and find out the incorrect statement.
A. Oils have lower melting point (e.g. gingely oil) and hence remain as oil in winters.
B. Nucleic acids like DNA and RNA consist of nucleotides only.
C. Adenosine, guanosine, cytosine, uridine and thymidine are nucleosides. ✓ Correct
D. Adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cytidylic acid are nucleotides.
Solution: Cytosine is a nitrogen base, not a nucleoside (the corresponding nucleoside is cytidine), so statement 2 is incorrect.
Q18 — Carbohydrates & Nucleic Acids · easy
Assertion: Starch gives blue colour in Iodine test. Reason: Starch can hold I2 molecules in its helical portion.
A. Both assertion and reason are true and the reason is the correct explanation of the assertion. ✓ Correct
B. Both assertion and reason are true, but reason is not the correct explanation of the assertion.
C. Both assertion and reason are false.
D. Assertion is true, but reason is false.
Solution: Starch turns blue with iodine because its helical structure traps iodine molecules, so the reason correctly explains the assertion.
Q19 — Carbohydrates & Nucleic Acids · medium
Assertion: Vegetable oils are fats which are present in plant cells in soluble form. Reason: Vegetable oils occur only in cells of embryo.
A. Assertion is true, but reason is false. ✓ Correct
B. Both assertion and reason are true and the reason is the correct explanation of the assertion.
C. Both assertion and reason are false.
D. Both assertion and reason are true, but reason is not the correct explanation of the assertion.
Solution: Vegetable oils do not occur only in embryo cells (they are found in various plant tissues), so the reason is false while the assertion holds.
Q20 — Carbohydrates & Nucleic Acids · easy
Assertion: Unsaturated fats are more reactive compared with the saturated fats. Reason: Unsaturated fats have only single bonds in their structure.
A. Both assertion and reason are true, but reason is not the correct explanation of the assertion.
B. Both assertion and reason are false.
C. Assertion is true, but reason is false. ✓ Correct
D. Both assertion and reason are true and the reason is the correct explanation of the assertion.
Solution: Unsaturated fats are more reactive due to their carbon-carbon double bonds, so the reason claiming only single bonds is false.
Q21 — Carbohydrates & Nucleic Acids · medium
Statement I: The molecules in the filtrate with the exception of lipids are polymeric substances. Statement II: Polysaccharides (carbohydrate) are polymers of monosaccharides.
A. Only statement II is correct
B. Both statement I and II are incorrect
C. Only statement I is correct
D. Both statement I and II are correct ✓ Correct
Solution: Both statements are correct. In the macromolecular (retentate/filtrate) fraction, the molecules except lipids are true polymers, and polysaccharides are polymers of monosaccharide units.
Q22 — Carbohydrates & Nucleic Acids · medium
Statement I: Paper is made from plant pulp and cotton fibre is cellulosic. Statement II: Palmitic acid has 16 carbons excluding carboxyl carbon.
A. Only statement II is correct
B. Both statement I and II are correct
C. Both statement I and II are incorrect
D. Only statement I is correct ✓ Correct
Solution: Statement I is correct — paper from plant pulp and cotton fibre are cellulosic. Statement II is incorrect: palmitic acid has 16 carbons including the carboxyl carbon (15 excluding it).
Q23 — Carbohydrates & Nucleic Acids · hard
Statement I: Oils have higher melting point (e.g., gingely oil) and hence remain as oil in winters. Statement II: Adenine and thymine are substituted purines while the guanine, cytosine and uracil are substituted pyrimidines.
A. Both statement I and II are correct
B. Only statement I is correct
C. Only statement II is correct
D. Both statement I and II are incorrect ✓ Correct
Solution: Both statements are incorrect. Oils have a lower melting point (e.g. gingely oil) and hence remain liquid in winter. Adenine and guanine are purines, while thymine, cytosine and uracil are pyrimidines — the statement misclassifies them.
Q24 — Carbohydrates & Nucleic Acids · medium
Match Column I with Column II. Column I: a. Uridine, b. Adenylic acid, c. Pyrimidine, d. Ribonucleic acid. Column II: 1. Nitrogen base, 2. Nucleoside, 3. Nucleic acid, 4. Nucleotide.
A. a-2, b-4, c-3, d-1
B. a-1, b-3, c-4, d-2
C. a-2, b-4, c-1, d-3 ✓ Correct
D. a-4, b-2, c-1, d-3
Solution: Uridine is a nucleoside (2), adenylic acid (AMP) is a nucleotide (4), pyrimidine is a nitrogen base (1), and ribonucleic acid is a nucleic acid (3). Hence a-2, b-4, c-1, d-3.
Q25 — Carbohydrates & Nucleic Acids · medium
Match Column I with Column II. Column I: a. Lecithin, b. Palmitic acid, c. Glycerol, d. Adenosine. Column II: 1. Nucleoside, 2. Trihydroxy propane, 3. Phospholipid, 4. Fatty acid.
A. a-4, b-3, c-2, d-1
B. a-3, b-4, c-2, d-1 ✓ Correct
C. a-3, b-4, c-1, d-2
D. a-4, b-3, c-1, d-2
Solution: Lecithin is a phospholipid (3), palmitic acid is a fatty acid (4), glycerol is trihydroxy propane (2), and adenosine is a nucleoside (1). Hence a-3, b-4, c-2, d-1.
Q26 — Carbohydrates & Nucleic Acids · hard
Match Column I with Column II. Column I: a. Insulin, b. Glycogen, c. Starch, d. Cellulose. Column II: i. Helical, ii. Glucose, iii. Fructose, iv. Nonhelical.
A. a-iii, b-i, c-ii, d-iv
B. a-iii, b-ii, c-i, d-iv ✓ Correct
C. a-ii, b-i, c-iii, d-iv
D. a-i, b-ii, c-iv, d-iii
Solution: Starch is helical (i), cellulose is nonhelical (iv), and glycogen is a polymer of glucose (ii). Among the given options, choice 3 (a-iii, b-ii, c-i, d-iv) correctly assigns starch-helical, cellulose-nonhelical and glycogen-glucose.
Q27 — Carbohydrates & Nucleic Acids · medium
Lecithin, a small molecular weight organic compound found in living tissues, is an example of:
A. Carbohydrates
B. Phospholipids ✓ Correct
C. Glycerides
D. Amino acids
Solution: Lecithin is a phospholipid found in the plasma membrane. It is a phosphorylated derivative of glycerol (a phosphoglyceride).
Q28 — Carbohydrates & Nucleic Acids · hard
Read the following statements on lipids and find out the correct set of statements:
(i) Lecithin found in the plasma membrane is a glycolipid.
(ii) Saturated fatty acids possess one or more C=C bonds.
(iii) Gingely oil has lower melting point, hence remains as oil in winter.
(iv) Lipids are generally insoluble in water but soluble in some organic solvents.
(v) When fatty acid is esterified with glycerol, monoglycerides are formed.
A. (i), (ii) and (iv) only
B. (i), (iv) and (v) only
C. (i), (ii) and (iii) only
D. (iii), (iv) and (v) only ✓ Correct
Solution: Lecithin is a phospholipid, not a glycolipid, so (i) is false. Saturated fatty acids have no C=C double bonds, so (ii) is false. Gingely oil (unsaturated) has a low melting point (iii-true); lipids are insoluble in water but soluble in organic solvents (iv-true); esterification of one fatty acid with glycerol gives a monoglyceride (v-true).
Q29 — Carbohydrates & Nucleic Acids · medium
A dehydration reaction links two glucose molecules to produce maltose. If the formula for glucose is C6H12O6, then what is the formula for maltose?
A. C12H24O12
B. C12H22O11 ✓ Correct
C. C12H20O10
D. C12H24O11
Solution: Two glucose (2 x C6H12O6 = C12H24O12) combine with loss of one water molecule (H2O) during dehydration, giving maltose C12H22O11.
Q30 — Carbohydrates & Nucleic Acids · hard
Following are the statements with reference to 'lipids':
(i) Lipids having only single bonds are called unsaturated fatty acids.
(ii) Lecithin is a phospholipid.
(iii) Trihydroxy propane is glycerol.
(iv) Palmitic acid has 20 carbon atoms including carboxyl carbon.
(v) Arachidonic acid has 16 carbon atoms.
Choose the correct answer.
A. (iii) and (iv) only
B. (i) and (ii) only
C. (ii) and (v) only
D. (ii) and (iii) only ✓ Correct
Solution: Lecithin is a phospholipid (ii-true) and trihydroxy propane is glycerol (iii-true). Only-single-bond fatty acids are saturated, not unsaturated (i-false); palmitic acid has 16 carbons, not 20 (iv-false); arachidonic acid has 20 carbons, not 16 (v-false).