Biomolecules: NEET MCQs where one word decides the answer

Free questions

30 solved MCQs, answer marked and reasoning written out

Every question below is free to read — no sign-up, no email. 2 of them are real questions from past NEET papers. The other 242 questions in this chapter are in the book and in practice access.

1. Q1 Multi-statement analysis

   Substrate concentration: (i) velocity rises at first with increasing substrate concentration (ii) the reaction reaches a maximum velocity, Vmax (iii) Vmax is not exceeded by further rise in substrate (iv) at saturation there are no free enzyme molecules to bind additional substrate. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.Three
   4. 4.FourCorrect answer

   Why option 4 is the answer

   The trap: All four are correct.

   What this is testing: how reaction velocity behaves as substrate concentration rises.

   All four are correct. (i) Velocity rises as substrate concentration increases. (ii) It reaches a maximum, Vmax. (iii) Adding still more substrate cannot push velocity past Vmax. (iv) At that saturation point, every enzyme molecule already has substrate bound, so none is free to take on more.

   These four statements build one continuous picture of the saturation curve, each explaining the next, so there is no contradiction to hunt for. Trust a list where each line is the mechanistic reason for the one before it.

   NCERT Class 11 Biology, page 116

2. Q2 Multi-statement analysis

   Regarding lipids in the macromolecular fraction: (i) lipids have molecular weights not exceeding 800 Da (ii) on grinding, membranes break into vesicles which are not water soluble (iii) these vesicles separate with the acid-insoluble pool (iv) lipids are strictly macromolecules. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; lipids are NOT strictly macromolecules, so (iv) is wrong.

   What this is testing: whether lipids count as true macromolecules.

   (i) is correct: lipid molecular weights stay under 800 Da. (ii) is correct: grinding tissue breaks membranes into vesicles that will not dissolve in water. (iii) is correct: those insoluble vesicles end up in the acid-insoluble pool along with the real macromolecules. (iv) is the trap. Despite sitting in that fraction, lipids are NOT strictly macromolecules — their low molecular weight in (i) already rules that out.

   So three are correct. Lipids land in the acid-insoluble fraction by insolubility, not by size — do not confuse 'where it separates' with 'what it is'.

   Acid-soluble is the small molecules; acid-insoluble is the macromolecules plus the membrane vesicles. Lipids land in the second by accident of size, not weight.

   NCERT Class 11 Biology, page 109

3. Q3 Multi-statement analysis

   Regarding molecular weights: (i) compounds of the acid-soluble pool have molecular weights of roughly 18 to 800 Da (ii) micromolecules have molecular weights less than one thousand dalton (iii) macromolecules are found in the acid-insoluble fraction (iv) macromolecules have molecular weights in the range of ten thousand daltons and above. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.Three
   4. 4.FourCorrect answer

   Why option 4 is the answer

   The trap: All four are correct.

   What this is testing: the molecular-weight boundaries that separate micromolecules from macromolecules.

   All four are correct. (i) Acid-soluble pool compounds run roughly 18 to 800 Da. (ii) Micromolecules are defined as under one thousand daltons. (iii) Macromolecules sit in the acid-insoluble fraction. (iv) Macromolecules run from about ten thousand daltons upward.

   These figures form one consistent scale from small to large, so nothing here is reversed. The only care needed is not to confuse the acid-soluble pool's small size (under 800 Da) with the much larger macromolecule threshold (10,000 Da and above) — the two numbers sit far apart on purpose.

   NCERT Class 11 Biology, page 108

4. Q4 Multi-statement analysis

   Comparing living tissue with the earth's crust: (i) all elements present in the earth's crust are also present in living tissue (ii) the relative abundance of carbon and hydrogen is higher in living organisms (iii) in absolute terms no difference in the element list can be made out (iv) living tissue contains elements entirely absent from the crust. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; no element is unique to living tissue, so (iv) is wrong.

   What this is testing: whether living tissue contains any element the earth's crust lacks.

   (i) is correct: every element in the crust also occurs in living tissue. (ii) is correct: carbon and hydrogen are relatively more abundant in organisms than in the crust. (iii) is correct: in absolute terms, no clear difference in the element list can be drawn. (iv) is the trap, directly contradicting (i) and (iii) by claiming living tissue has elements the crust entirely lacks.

   So three are correct. No element is unique to life — what differs is proportion (more carbon and hydrogen), not the list of elements itself.

   Same elements, different proportions. Life is built from ordinary crust chemistry assembled in unusual ratios.

   NCERT Class 11 Biology, page 104

5. Q5 Multi-statement analysis

   Regarding amino acids: (i) the –NH2 and –COOH groups are ionizable (ii) the structure of amino acids changes with the pH of the solution (iii) the zwitterionic form bears both a positive and a negative charge (iv) the R group determines the identity of the amino acid. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.Three
   4. 4.FourCorrect answer

   Why option 4 is the answer

   The trap: All four are correct.

   What this is testing: how an amino acid's charge and identity are determined.

   All four are correct. (i) The –NH2 and –COOH groups can ionise. (ii) The amino acid's structure shifts with the pH of its solution. (iii) The zwitterion carries both a positive and a negative charge at once. (iv) The R group is what makes each amino acid different from the rest.

   These four move from the ionisable groups, to how pH affects them, to the resulting charged (zwitterionic) form, and finally to what varies between amino acids — a coherent sequence with nothing contradicted. Zwitterion is the key word to hold on to: 'both charges at once', not 'no charge'.

   NCERT Class 11 Biology, page 106

6. Q6 Multi-statement analysis

   Protein primary structure: (i) the first amino acid is the N-terminal amino acid (ii) the last amino acid is the C-terminal amino acid (iii) it represents the positional information of the amino acids (iv) it gives the three-dimensional view of the protein. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; the TERTIARY structure gives the 3-D view, so (iv) is wrong.

   What this is testing: what the primary structure of a protein tells you, and what it does not.

   (i) is correct: the first amino acid is the N-terminal one. (ii) is correct: the last is the C-terminal one. (iii) is correct: the primary structure is exactly this positional information — which amino acid sits where. (iv) is the trap. The three-dimensional view of a protein comes from its TERTIARY structure, not the primary structure, which is just a flat sequence.

   So three are correct. Primary structure is a 1-D list of amino acids in order; only folding, described by higher structural levels, gives it a shape in 3-D space.

   Primary structure is sequence alone - N-terminal to C-terminal. Shape belongs to the tertiary level.

   NCERT Class 11 Biology, page 112

7. Q7 Multi-statement analysis

   Amino acids in nutrition: (i) essential amino acids must be supplied through the diet (ii) non-essential amino acids can be made by the body (iii) dietary proteins are the source of essential amino acids (iv) all twenty amino acids are essential. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; only some amino acids are essential, so (iv) is wrong.

   What this is testing: the difference between essential and non-essential amino acids.

   (i) is correct: essential amino acids must come from the diet. (ii) is correct: non-essential ones can be synthesised by the body itself. (iii) is correct: dietary protein is the source of the essential ones. (iv) is the trap. Not all twenty amino acids are essential — only some of them are, with the rest made by the body.

   So three are correct. 'Essential' means the body cannot make it, so it must be eaten; treating all twenty as essential erases the whole point of the essential/non-essential split.

   Essential means the body cannot make it, not that it matters more. Nine of the twenty have to come from food.

   NCERT Class 11 Biology, page 109

8. Q8 Multi-statement analysis

   Regarding protein helices: (i) the thread is folded in the form of a helix (ii) only some portions of the protein thread are helical (iii) in proteins only right-handed helices are observed (iv) both right- and left-handed helices are equally common in proteins. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; only RIGHT-handed helices occur in proteins, so (iv) is wrong.

   What this is testing: the handedness of the helices found in protein secondary structure.

   (i) is correct: the protein thread folds into a helix. (ii) is correct: only some stretches of the thread are helical, not the whole chain. (iii) is correct: proteins show only right-handed helices. (iv) is the trap, directly contradicting (iii) by claiming left-handed helices are equally common.

   So three are correct. Biological helices in proteins are consistently right-handed; a 'both types occur equally' claim is the kind of invented balance that NEET likes to plant as the wrong option.

   Only right-handed helices in proteins, and only along parts of the chain. Handedness is fixed by the chemistry of L-amino acids.

   NCERT Class 11 Biology, page 112

9. Q9 Assertion and Reason

   AssertionEnzymes show a narrow range of optimum temperature.

   ReasonLow temperature preserves the enzyme in a temporarily inactive state.

   1. 1.Both A and R are true and R is the correct explanation of A
   2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
   3. 3.A is true but R is false
   4. 4.A is false but R is true

   Why option 2 is the answer

   The trap: Both are true of enzymes and temperature; the preservative effect of cold is a parallel fact and does not explain the narrow optimum.

   What this is testing: whether cold and heat affect enzymes for the same reason.

   Both statements are true, but R does not explain A. Enzymes do show a narrow optimum temperature range, and separately, cold does preserve them in a temporarily inactive rather than destroyed state — but that preservative effect of low temperature does not explain WHY the optimum range itself is narrow.

   The trap is pairing two genuine facts that sit side by side in the text without one causing the other; recognise that a narrow optimum and cold-preservation are two different observations about temperature, not cause and effect.

   NCERT Class 11 Biology, page 116

10. Q10 Assertion and Reason

    AssertionSecondary metabolites are useful to human welfare.

    ReasonThe role or function of many secondary metabolites in the host organism is still not understood.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true of secondary metabolites; our ignorance of their host functions is a parallel fact and does not explain their usefulness to humans.

    What this is testing: whether being useful to humans and being understood by science are the same thing.

    Both statements are true, but R does not explain A. Secondary metabolites are genuinely useful to human welfare, and separately, we genuinely do not understand the role many of them play in their own host organism — but our ignorance of the second point is not the reason for the first.

    The trap invites you to link 'usefulness' with 'mystery', but a compound can be medically valuable to humans while its purpose to the plant that makes it stays unknown; the two facts run in parallel, not as cause and effect.

    NCERT Class 11 Biology, page 108

11. Q11 Assertion and Reason

    AssertionOils remain liquid in winter whereas fats do not.

    ReasonBoth fats and oils are glycerides in which fatty acids are esterified to glycerol.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true of glycerides; their shared chemical construction is a parallel fact and does not explain why oils stay liquid.

    What this is testing: what actually distinguishes an oil from a fat.

    Both statements are true, but R does not explain A. Fats and oils being glycerides with fatty acids esterified to glycerol is a shared structural fact about both, but it does not explain why one stays liquid in winter and the other does not — that difference comes from melting point, which in turn depends on how saturated the fatty acid chains are.

    The trap offers a true but generic fact about glycerides as if it explained a specific behavioural difference; shared chemistry cannot explain a difference between two members of the same group.

    NCERT Class 11 Biology, page 106

12. Q12 Assertion and Reason

    AssertionLipids are recovered in the acid-insoluble (macromolecular) fraction although their molecular weight does not exceed 800 Da.

    ReasonOn grinding, membranes break into vesicles that are not water soluble and hence sediment with the acid-insoluble pool.

    1. 1.Both A and R are true and R is the correct explanation of ACorrect answer
    2. 2.Both A and R are true but R is not the correct explanation of A
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 1 is the answer

    The trap: R explains why small lipids appear in the macromolecular fraction.

    What this is testing: why small lipid molecules end up in the large-molecule (acid-insoluble) fraction.

    Both statements are true, and R explains A. Lipids stay under 800 Da, well below the macromolecule range, but grinding breaks their membranes into vesicles that will not dissolve in water — and that insolubility, not size, is what lets them settle with the acid-insoluble pool.

    This is a clean mechanism pairing: the reason explains the apparent contradiction in the assertion (small molecule, large-molecule fraction) rather than a size-based rule.

    NCERT Class 11 Biology, page 109

13. Q13 Assertion and Reason

    AssertionInorganic catalysts are damaged at high temperatures whereas enzymes work best there.

    ReasonEnzymes are damaged above about 40°C, while inorganic catalysts work efficiently at high temperatures and pressures.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of A
    3. 3.A is true but R is false
    4. 4.A is false but R is trueCorrect answer

    Why option 4 is the answer

    The trap: A is false — the properties are reversed; R is true.

    What this is testing: which kind of catalyst — enzyme or inorganic — actually tolerates high temperature.

    A is false: it reverses the real pattern. Enzymes are the ones damaged above about 40°C, while inorganic catalysts are the ones that work efficiently at high temperature and pressure. R is true and states this correctly.

    The trap swaps the two catalyst types' properties onto each other. Keep it straight: biological (protein) catalysts are heat-sensitive, industrial inorganic catalysts are heat-tolerant.

    NCERT Class 11 Biology, page 113

14. Q14 Assertion and Reason

    AssertionEnzyme-catalysed reactions proceed at rates vastly higher than uncatalysed ones.

    ReasonIn the presence of carbonic anhydrase about 600,000 molecules of carbonic acid are formed every second.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true; the carbonic anhydrase figure is a parallel illustration rather than the explanation of the general rule.

    What this is testing: whether a single named example explains the general rule about enzyme speed.

    Both statements are true, but R does not explain A. Enzyme reactions being far faster than uncatalysed ones is a general rule, and carbonic anhydrase forming 600,000 molecules per second is one striking illustration of it — but that one figure is an example of the rule, not the reason the rule holds in general.

    The trap substitutes a specific number for a general explanation; an illustration supports a claim, it does not cause it.

    NCERT Class 11 Biology, page 114

15. Q15 Assertion and Reason

    AssertionGlycerol is a monohydroxy propane.

    ReasonGlycerol is trihydroxy propane and its hydroxyl groups can be esterified with fatty acids.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of A
    3. 3.A is true but R is false
    4. 4.A is false but R is trueCorrect answer

    Why option 4 is the answer

    The trap: A is false; R is true.

    What this is testing: how many hydroxyl groups glycerol actually has.

    A is false: glycerol is a TRIhydroxy propane, not monohydroxy — it carries three hydroxyl groups, not one. R is true and gives the correct description, adding that those hydroxyls can be esterified with fatty acids.

    The trap understates glycerol's structure by a false number. Three hydroxyl groups is also why glycerol can bind up to three fatty acids to form mono-, di- or triglycerides — one hydroxyl group could never do that.

    NCERT Class 11 Biology, page 106

16. Q16 Assertion and Reason

    AssertionTrichloroacetic acid is used to separate the acid-soluble and acid-insoluble fractions of a tissue.

    ReasonThe acid-soluble pool roughly represents the cytoplasmic composition of the cell.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true; the identity of the acid-soluble pool is a parallel fact and does not explain the use of the acid.

    What this is testing: what trichloroacetic acid is used for, and what the resulting acid-soluble pool represents.

    Both statements are true, but R does not explain A. Trichloroacetic acid genuinely separates tissue into acid-soluble and acid-insoluble fractions, and the acid-soluble pool genuinely represents roughly the cytoplasmic composition — but knowing what that pool represents does not explain why the acid is used to separate the fractions in the first place.

    The trap again links two true but independently stated facts; the acid's separating action and the pool's biological meaning are two different points in the text.

    NCERT Class 11 Biology, page 109

17. Q17 Assertion and Reason

    AssertionCollagen is the most abundant protein in the animal world.

    ReasonRuBisCO is the most abundant protein in the whole of the biosphere.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true abundance facts about different proteins running in parallel; one does not explain the other.

    What this is testing: which protein is most abundant in animals versus across the whole biosphere.

    Both statements are true, but R does not explain A. Collagen tops the list in the animal world, and RuBisCO tops the list across the whole biosphere — but these describe two different scopes (animals alone vs. all life), so one fact does not cause or explain the other.

    The trap uses two correct abundance facts about different proteins to suggest a link that is not there; each statement stands on its own within its own scope.

    NCERT Class 11 Biology, page 110

18. Q18 Statement I and Statement II

    Statement ILipids are strictly macromolecules.

    Statement IILipids appear in the acid-insoluble fraction because membrane fragments form water-insoluble vesicles.

    1. 1.Both Statement I and Statement II are correct
    2. 2.Both Statement I and Statement II are incorrect
    3. 3.Statement I is correct but Statement II is incorrect
    4. 4.Statement I is incorrect but Statement II is correctCorrect answer

    Why option 4 is the answer

    The trap: I incorrect (lipids are not strictly macromolecules); II correct.

    What this is testing: whether lipids truly qualify as macromolecules by weight.

    Statement I is incorrect: lipids are NOT strictly macromolecules — their molecular weight stays under 800 Da, well short of the macromolecule range. Statement II is correct: lipids still turn up in the acid-insoluble fraction because grinding breaks membranes into water-insoluble vesicles.

    The trap tests whether a student conflates 'where a molecule separates' (by solubility) with 'what class it belongs to' (by size) — a lipid can be small and still land in the insoluble fraction, for the reason Statement II gives.

    NCERT Class 11 Biology, page 109

19. Q19 Statement I and Statement II

    Statement IStarch can hold iodine molecules in its helical portion, giving a blue colour.

    Statement IICellulose contains complex helices and also holds iodine.

    1. 1.Both Statement I and Statement II are correct
    2. 2.Both Statement I and Statement II are incorrect
    3. 3.Statement I is correct but Statement II is incorrectCorrect answer
    4. 4.Statement I is incorrect but Statement II is correct

    Why option 3 is the answer

    The trap: I correct; cellulose lacks such helices and cannot hold I2, so II is incorrect.

    What this is testing: why starch reacts with iodine but cellulose does not.

    Statement I is correct: starch's helical structure traps iodine and gives a blue colour. Statement II is incorrect: cellulose LACKS such complex helices and so CANNOT hold iodine — the statement wrongly extends starch's property to cellulose.

    The trap gives cellulose a structure it does not have. Cellulose's straight, hydrogen-bonded chains give it mechanical strength, not the coiled shape needed to trap I2 molecules.

    NCERT Class 11 Biology, page 110

20. Q20 Statement I and Statement II

    Statement IThe primary structure of a protein is its amino acid sequence.

    Statement IIThe secondary structure gives the three-dimensional view of a protein.

    1. 1.Both Statement I and Statement II are correct
    2. 2.Both Statement I and Statement II are incorrect
    3. 3.Statement I is correct but Statement II is incorrectCorrect answer
    4. 4.Statement I is incorrect but Statement II is correct

    Why option 3 is the answer

    The trap: I correct; the TERTIARY structure gives the 3-D view, so II is incorrect.

    What this is testing: which structural level gives a protein its 3-D shape.

    Statement I is correct: the primary structure is indeed the amino acid sequence. Statement II is incorrect: it is the TERTIARY structure, not the secondary structure, that gives a protein its three-dimensional folded view.

    The trap moves the 3-D property down one level too early. Secondary structure only describes local folding, like helices and pleated sheets; the full three-dimensional shape only appears once tertiary folding is complete.

    NCERT Class 11 Biology, page 111

21. Q21 Match the columns

    Match the nitrogen base with its type:

    Column I	Column II
    (a) Adenine	(iii) pyrimidine
    (b) Guanine	(i) pyrimidine
    (c) Cytosine	(iv) purine
    (d) Uracil	(ii) purine

    1. 1.(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
    2. 2.(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
    3. 3.(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
    4. 4.(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)Correct answer

    Why option 4 is the answer

    The trap: Adenine and guanine-purines; cytosine and uracil-pyrimidines.

    What this is testing: sorting four nitrogen bases correctly into purines and pyrimidines.

    The correct pairing is option 4: adenine and guanine are purines, cytosine and uracil are pyrimidines. Option 1 assigns adenine and guanine to pyrimidine and cytosine and uracil to purine, reversing both classes at once.

    Only two bases are purines — adenine and guanine — and everything else in this list is a pyrimidine; fixing that short purine list in memory settles the whole match instantly.

    NCERT Class 11 Biology, page 111

22. Q22 Match the columns

    Match the metabolic end product with the condition:

    Column I	Column II
    (a) Skeletal muscle, anaerobic	(iii) ethanol
    (b) Normal aerobic conditions	(iv) ten enzyme-catalysed steps
    (c) Yeast, fermentation	(i) lactic acid
    (d) Glucose to pyruvic acid	(ii) pyruvic acid

    1. 1.(a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
    2. 2.(a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
    3. 3.(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
    4. 4.(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)Correct answer

    Why option 4 is the answer

    The trap: Anaerobic muscle-lactic acid, aerobic-pyruvic acid, yeast-ethanol, glycolysis-ten steps.

    What this is testing: matching glucose breakdown end-products to the conditions that produce them.

    The correct pairing is option 4: anaerobic skeletal muscle produces lactic acid, normal aerobic conditions give pyruvic acid, yeast fermentation gives ethanol, and the conversion of glucose to pyruvic acid takes ten enzyme-catalysed steps. Option 1 swaps the anaerobic-muscle and aerobic products.

    The organism and the oxygen condition decide the end product: muscle without oxygen makes lactic acid, yeast without oxygen makes ethanol, and with oxygen present the pathway simply stops at pyruvic acid.

    NCERT Class 11 Biology, page 114

23. Q23 Match the columns

    Match the sugar with its formula/type:

    Column I	Column II
    (a) Glucose	(i) sugar of RNA
    (b) Ribose	(ii) sugar of DNA
    (c) Deoxyribose	(iii) C5H10O5
    (d) Ribose	(iv) C6H12O6

    1. 1.(a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
    2. 2.(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)Correct answer
    3. 3.(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
    4. 4.(a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)

    Why option 2 is the answer

    The trap: Glucose-C6H12O6, Ribose-C5H10O5 and the RNA sugar, Deoxyribose-the DNA sugar.

    What this is testing: matching each sugar to its formula or its role in DNA versus RNA.

    The correct pairing is option 2: glucose is C6H12O6, ribose is C5H10O5 and the sugar of RNA, while deoxyribose is the sugar of DNA. Option 1 swaps glucose and ribose's formulas.

    The row structure here repeats ribose deliberately to link both its formula and its RNA role in one place — do not let that repetition distract you from checking deoxyribose's separate pairing with DNA.

    NCERT Class 11 Biology, page 111

24. Q24 Match the columns

    Match the step of the catalytic cycle with its order:

    Column I	Column II
    (a) First	(iv) product released, free enzyme regenerated
    (b) Second	(i) bonds broken, EP complex formed
    (c) Third	(iii) enzyme alters shape, fits tightly
    (d) Fourth	(ii) substrate binds the active site

    1. 1.(a)-(ii), (b)-(iii), (c)-(i), (d)-(iv)Correct answer
    2. 2.(a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
    3. 3.(a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
    4. 4.(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)

    Why option 1 is the answer

    The trap: Binding → induced fit → bond breaking/EP complex → product release.

    What this is testing: putting the four steps of the enzyme catalytic cycle in their correct order.

    The correct order is option 1: substrate binds the active site, the enzyme alters shape to fit tightly, bonds break and the EP complex forms, and finally the product is released, regenerating free enzyme. Option 2 swaps steps one and two, putting the shape change before binding.

    The sequence only makes physical sense one way — binding must happen before the enzyme can adjust its shape around the substrate — so trace the physical story rather than memorising four disconnected labels.

    NCERT Class 11 Biology, page 115

25. Q25 Exception / incorrect

    All are true of a glycogen chain EXCEPT:

    1. 1.the right end is the reducing end
    2. 2.the left end is the non-reducing end
    3. 3.it has branches
    4. 4.the left end is the reducing endCorrect answer

    Why option 4 is the answer

    The trap: The right end is the reducing end.

    What this is testing: which end of a glycogen chain is truly the reducing end.

    Options 1 to 3 are true of a glycogen chain: the right end is the reducing end, the left end is the non-reducing end, and the chain does have branches. Option 4 is the exception, directly contradicting option 1 by placing the reducing end on the left instead of the right.

    The trap repeats the correct rule earlier in the list and then reverses it later — whenever two options in the same set assign opposite ends to the same term, one of them must be the planted error.

    NCERT Class 11 Biology, page 110

26. Q26 Exception / incorrect

    All are true of the primary structure EXCEPT:

    1. 1.it is the amino acid sequence
    2. 2.the first amino acid is the N-terminal
    3. 3.the last amino acid is the C-terminal
    4. 4.it gives the three-dimensional viewCorrect answer

    Why option 4 is the answer

    The trap: The tertiary structure gives the 3-D view.

    What this is testing: what the primary structure of a protein actually shows, and what it does not.

    Options 1 to 3 are true of the primary structure: it is the amino acid sequence, the first amino acid is N-terminal, and the last is C-terminal. Option 4 is the exception: it is the TERTIARY structure, not the primary structure, that gives a protein its three-dimensional view.

    The trap assigns a higher structural level's defining feature (3-D shape) to the lowest level; primary structure is only a flat, ordered list of amino acids with no shape information of its own.

    NCERT Class 11 Biology, page 112

27. Q27 Sequence / ordering

    Correct order of a metabolic pathway in yeast during fermentation:

    1. 1.ethanol → pyruvic acid → glucose
    2. 2.pyruvic acid → glucose → ethanol
    3. 3.ethanol → glucose → pyruvic acid
    4. 4.glucose → pyruvic acid → ethanolCorrect answer

    Why option 4 is the answer

    The trap: Glucose → pyruvic acid → ethanol in fermentation.

    What this is testing: the correct order of the fermentation pathway in yeast.

    The correct order is option 4: glucose → pyruvic acid → ethanol. Yeast breaks glucose down to pyruvic acid through the same ten-step glycolysis used elsewhere, then converts that pyruvic acid to ethanol under fermentation. Options 1 to 3 all scramble this order, for instance placing ethanol before glucose.

    Every breakdown pathway in this chapter starts from glucose and ends at a specific product depending on the organism and oxygen conditions — for yeast under fermentation, that end product is ethanol.

    NCERT Class 11 Biology, page 114

28. Q28 Sequence / ordering

    Correct order in the classification of enzymes:

    1. 1.oxidoreductases → transferases → hydrolases → lyases → isomerases → ligasesCorrect answer
    2. 2.ligases → isomerases → lyases → hydrolases → transferases → oxidoreductases
    3. 3.hydrolases → oxidoreductases → ligases → lyases → transferases → isomerases
    4. 4.transferases → hydrolases → oxidoreductases → isomerases → ligases → lyases

    Why option 1 is the answer

    The trap: The six classes are listed in this order in NCERT.

    What this is testing: recall of the fixed order in which the six enzyme classes are listed.

    The correct order is option 1: oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases — the exact sequence NCERT uses. Options 2 to 4 all scramble this order in different ways, for instance starting from ligases and working backwards.

    This is the order used to number enzymes internationally (class 1 through class 6), so treat it as a fixed list to memorise in sequence rather than six independent facts to recall in any order.

    NCERT Class 11 Biology, page 117

29. Q29 NEET 2024 (Re-Exam)

    Which of the following are NOT fatty acids: (A) Glutamic acid (B) Arachidonic acid (C) Palmitic acid (D) Lecithin (E) Aspartic acid? How many of the above are NOT fatty acids?

    1. 1.Two
    2. 2.ThreeCorrect answer
    3. 3.Four
    4. 4.Five

    Why option 2 is the answer

    The trap: (A) glutamic acid and (E) aspartic acid are amino acids and (D) lecithin is a phospholipid, none of them fatty acids; only (B) arachidonic acid and (C) palmitic acid are fatty acids — three are NOT fatty acids.

    What this is testing: sorting five named compounds correctly into fatty acids and non-fatty-acids.

    (A) glutamic acid and (E) aspartic acid are both amino acids, not fatty acids, and (D) lecithin is a phospholipid, also not a fatty acid - three compounds that are NOT fatty acids, giving option 2.

    (B) arachidonic acid and (C) palmitic acid are the genuine fatty acids in this list, and are the ones the question is NOT asking about.

    NCERT Class 11 Biology, page 109

30. Q30 NEET 2017

    Choose the correct statement about enzymes:

    1. 1.Holoenzyme = Apoenzyme + CoenzymeCorrect answer
    2. 2.Holoenzyme = Coenzyme + Cofactor
    3. 3.Apoenzyme = Holoenzyme + Coenzyme
    4. 4.Coenzyme = Apoenzyme + Holoenzyme

    Why option 1 is the answer

    The trap: A holoenzyme is the catalytically active apoenzyme-coenzyme complex.

    What this is testing: recall of the correct relationship between holoenzyme, apoenzyme and coenzyme.

    A holoenzyme is formed by combining the apoenzyme (protein portion) with its coenzyme (non-protein helper), so holoenzyme equals apoenzyme plus coenzyme, matching option 1.

    Option 2 is the trap that leaves the protein portion out entirely, wrongly defining the holoenzyme from coenzyme and cofactor alone. Option 3 flips the equation around, wrongly making apoenzyme the sum of the other two. Option 4 flips it again in a different direction, making coenzyme the combined total.

    NCERT Class 11 Biology, page 118