Every Biomolecules question (Unit 1) CSIR-NET Life Sciences has set in its last 11 papers, sorted by topic, with 16 of them solved step by step. Answers follow NTA’s final answer keys.
Unit 1 of the CSIR-NET Life Sciences syllabus, Molecules and their Interaction Relevant to Biology, is biochemistry: chemical bonds and water, the structure of biomolecules, protein and nucleic acid conformation, enzyme kinetics, bioenergetics and metabolism. We went through all 11 papers from February 2022 to June 2025 and pulled out every question from this unit. Many of them are short calculations.
How much of the paper is Biomolecules and Biochemistry?
Across the 11 papers, 111 of the 1,375 Part B and Part C questions (8.1%) came from Unit 1. That ranks it sixth of the 13 units. 65 of the 111 were 4-mark Part C questions.
| Paper | Part B | Part C | Total |
|---|---|---|---|
| June 2025 | 5 | 6 | 11 |
| December 2024, Shift 1 | 4 | 7 | 11 |
| December 2024, Shift 2 | 3 | 6 | 9 |
| June 2024, Shift 1 | 4 | 6 | 10 |
| June 2024, Shift 2 | 4 | 7 | 11 |
| December 2023, Shift 1 | 4 | 7 | 11 |
| December 2023, Shift 2 | 4 | 4 | 8 |
| June 2023, Shift 1 | 4 | 6 | 10 |
| June 2023, Shift 2 | 4 | 6 | 10 |
| February 2022, Shift 1 | 5 | 3 | 8 |
| February 2022, Shift 2 | 5 | 7 | 12 |
| All 11 papers | 46 | 65 | 111 |
Which Biomolecules and Biochemistry topics come up most
Protein Conformation & Stability and Enzymes – Catalysis & Kinetics together account for 37% of the unit’s questions.
16 solved Biomolecules and Biochemistry PYQs
One or two from each major subtopic, from different papers. Try each one before you open the solution.
If 19% of the nucleotides in a genome are “A”, what percent are “C”, “G”, and “T”?
- 1C = 31%, G = 31%, and T = 19%
- 2C = 19%, G = 19%, and T = 31%
- 3C = 31%, G = 19%, and T = 31%
- 4C = 19%, G = 31%, and T = 31%
Show answer and solution
In double-stranded DNA, A pairs with T and G with C, so A = T and G = C (Chargaff’s rules). With A = 19%, T = 19%. That leaves 100 − 38 = 62% for G + C, split equally: G = C = 31%.
The base composition of the genome of a newly identified virus is given below:
Adenine: 25%; Cytosine: 35%; Guanine: 30%; Thymidine: 10%
Based on this information, the genome of this virus is:
- 1double-stranded DNA.
- 2single-stranded DNA.
- 3double-stranded RNA.
- 4single-stranded RNA.
Show answer and solution
In double-stranded DNA, A would equal T and G would equal C. Here A (25%) is not equal to T (10%), and G (30%) is not equal to C (35%), so the strands are not paired. Thymine shows it is DNA, not RNA (RNA has uracil). The genome is single-stranded DNA, as in phage φX174.
The pH of endocytic vesicles is 5.2, and the pH of gastric juice is 2.0. The endocytic vesicle has a [H+] that is
- 115.85 times lower than that of gastric juice.
- 20.1585 times lower than that of gastric juice.
- 3158.5 times lower than that of gastric juice.
- 41585 times lower than that of gastric juice.
Show answer and solution
Answer: (4) 1585 times lower than that of gastric juice.
pH is −log[H+], so a difference of 5.2 − 2.0 = 3.2 pH units is a 103.2-fold difference in [H+]. 103.2 ≈ 1,585. The endocytic vesicle, at the higher pH, has 1,585 times less H+ than gastric juice.
What is the pH of a 10−7 M solution of HCl?
- 16.00
- 26.79
- 37.00
- 47.50
Show answer and solution
Answer: (2) 6.79
At 10−7 M the acid is so dilute that the water’s own H+ cannot be ignored (and the answer cannot be pH 7). Solve [H+]2 − 10−7[H+] − 10−14 = 0, which gives [H+] = 1.62 × 10−7 M and pH = 6.79. Slightly acidic, as an acid should be.
What is the V0/Vmax ratio for an enzymatic reaction when [S] = 3 Km and 9 Km, respectively?
- 10.65 and 0.83
- 20.55 and 1.0
- 30.93 and 1.2
- 40.75 and 0.9
Show answer and solution
Answer: (4) 0.75 and 0.9
From the Michaelis–Menten equation, v/Vmax = [S]/(Km + [S]). At [S] = 3Km: 3/4 = 0.75. At [S] = 9Km: 9/10 = 0.90. Tripling [S] again adds only 15 percentage points, because the enzyme is near saturation.
What is the fold difference between v at [S] = Km and v at [S] = 1000Km, where v is the initial velocity of an enzyme catalyzed reaction, [S] is substrate concentration and Km is the Michaelis constant?
- 11.998
- 21000
- 32.998
- 43.998
Show answer and solution
Answer: (1) 1.998
At [S] = Km, v = Vmax/2. At [S] = 1000Km, v = Vmax × 1000/1001 = 0.999Vmax. The ratio is 0.999 ÷ 0.5 = 1.998. A thousand-fold more substrate only doubles the rate.
How many hydrogen bonds involving the backbone CO and NH can be observed in an α-helix consisting of 15 amino acid residues?
- 110
- 211
- 312
- 413
Show answer and solution
Answer: (2) 11
In an α-helix the C=O of residue i bonds to the N–H of residue i + 4. The first four N–H groups and the last four C=O groups have no partner inside the helix, so an n-residue helix has n − 4 backbone hydrogen bonds: 15 − 4 = 11.
The central rod domain of keratin protein is 300 amino acids in length. What is the approximate length (in Å) of the rod domain if the peptide consists of
(i) distorted α-helix
(ii) true α-helix
(iii) anti-parallel β-sheet
- 1(i) 425 Å; (ii) 450 Å; (iii) 1041 Å
- 2(i) 450 Å; (ii) 450 Å; (iii) 840 Å
- 3(i) 425 Å; (ii) 425 Å; (iii) 1004 Å
- 4(i) 340 Å; (ii) 425 Å; (iii) 104 Å
Show answer and solution
Answer: (1) (i) 425 Å; (ii) 450 Å; (iii) 1041 Å
Each residue adds about 1.5 Å to a true α-helix, so 300 × 1.5 = 450 Å. In a coiled coil the helices wind round each other, which shortens the rise to about 1.42 Å, giving about 425 Å. An antiparallel β-strand is almost fully extended at about 3.47 Å per residue, giving about 1,041 Å.
The standard free energy (kJ mol−1) of hydrolysis of glucose-1-phosphate is:
- 1−40.3
- 2−35.8
- 3−7.7
- 4−20.9
Show answer and solution
Answer: (4) −20.9
Glucose-1-phosphate is a sugar phosphate ester with a fairly low phosphoryl-transfer potential: ΔG°′ of hydrolysis = −20.9 kJ/mol. Compare ATP to ADP (−30.5), phosphocreatine (−43) and PEP (−61.9) above it, and glucose-6-phosphate (−13.8) below it.
Which one of the following bonds support the three intertwined polypeptide strands in the triple helical structure of collagen?
- 1Disulfide bonds
- 2Hydrogen bonds
- 3Co-ordinate bonds
- 4Ionic bonds
Show answer and solution
Answer: (2) Hydrogen bonds
Each collagen chain is a left-handed polyproline II helix with a Gly–X–Y repeat. Three chains wind into a right-handed superhelix held together by interchain hydrogen bonds. The N–H of each glycine bonds to a C=O on a neighbouring chain, and hydroxyproline adds further water-mediated hydrogen bonds. Collagen has essentially no disulfides in the helix. Its cross-links are lysine-derived covalent bonds formed later.
Which one of the following properties of grooves is a hallmark of the Z-form of DNA?
- 1Narrow and deep major groove
- 2Wide and deep major groove
- 3Narrow and shallow major groove
- 4Flat major groove
Show answer and solution
Answer: (4) Flat major groove
Z-DNA is a left-handed zig-zag helix with alternating syn and anti bases. Its “major groove” is pushed out to the surface until it is essentially flat, while the minor groove is narrow and deep. B-DNA has a wide, deep major groove, and A-DNA a narrow, deep one.
What is the net charge of the peptide Tyr-Val-Arg at pH 5.0? The pKas of alpha amino and carboxyl groups are 9.6 and 2.3, respectively. The pKas of Tyr and Arg side chains are 10.46 and 12.48, respectively.
- 11.0
- 25
- 32.5
- 411
Show answer and solution
Answer: (1) 1.0
At pH 5.0 the α-amino group (pKa 9.6) is protonated: +1. The α-carboxyl (pKa 2.3) is ionised: −1. The Arg side chain (12.48) is protonated: +1. The Tyr phenol (10.46) is neutral: 0. Net charge = +1.
An enzyme “X” converts a L-amino acid to a racemic mixture of D- and L- forms. Which one of the following coenzymes is utilized by enzyme X for this conversion?
- 1Pyridoxal phosphate
- 2Thiamine pyrophosphate
- 3Flavin adenine dinucleotide
- 4Tetrahydrofolate
Show answer and solution
Answer: (1) Pyridoxal phosphate
Amino acid racemases (for example alanine racemase, which makes D-Ala for the bacterial cell wall) use pyridoxal phosphate. The amino acid forms a Schiff base with PLP, and PLP stabilises the carbanion left when the α-hydrogen is removed. The proton can then return from either face, giving D and L. TPP, FAD and THF carry out other kinds of chemistry.
Following are the pKa’s of the ionizable groups in lysine
pKa1 = 2.16 (α – carboxylic group)
pKa2 = 9.06 (α – amino group)
pKa3 = 10.54 (ε – amino group)
Which one of the following options represents the pI of lysine?
- 17.25
- 25.61
- 36.35
- 49.8
Show answer and solution
Answer: (4) 9.8
For lysine the pI lies between the two pKas that flank the neutral (zwitterionic) form, which are the α-amino and ε-amino groups. pI = (9.06 + 10.54)/2 = 9.8. Lysine is basic, so its pI is well above 7.
The solubility of NaCl is greater in water than ethanol. What physical property of the solvent governs this difference?
- 1Surface tension
- 2Viscosity
- 3Dielectric constant
- 4Boiling point
Show answer and solution
Answer: (3) Dielectric constant
Water’s dielectric constant (about 80) is much higher than ethanol’s (about 24). By Coulomb’s law the attraction between Na+ and Cl− is inversely proportional to the dielectric constant, so water screens the ions from each other far better and holds them apart in solution.
Phosphofructokinase catalyses one of the regulatory steps in glycolysis. Which one of the following metabolic changes leads to the activation of phosphofructokinase?
- 1Increased ATP concentration
- 2Decreased AMP concentration
- 3High citrate levels
- 4Increased fructose 2, 6 bisphosphate concentration
Show answer and solution
Answer: (4) Increased fructose 2, 6 bisphosphate concentration
Fructose 2,6-bisphosphate, made by PFK-2 when insulin and glucose are high, is the most potent allosteric activator of PFK-1. It raises the enzyme’s affinity for fructose-6-phosphate and overrides ATP inhibition. Rising ATP, falling AMP and high citrate all signal plenty of energy and inhibit PFK-1.
All 111 Biomolecules and Biochemistry questions, by subtopic
Each link opens the question on its full paper page. Press Show answer and solution there to see NTA’s final key and a worked solution.
Protein Conformation & Stability (22 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q65 | B | Which one of the following is the correct arrangement of amino acid dipeptides in increasing order of the area of allowed regions in the… |
| Jun 2025, Q129 | C | Given below are thermal melting curves for proteins A, P, Q and R. The X-axis denotes temperature, while the Y-axis indicates the… |
| Jun 2025, Q134 | C | An alpha helix formed by 30 residues is stabilized by 25 backbone hydrogen bonds in its folded state. Assume that the average energy of a… |
| Dec 2024 S1, Q73 | C | A cytoplasmic monomeric protein containing a single non-surface exposed cysteine residue precipitates upon mutation of the Cys to ‘Ile’… |
| Dec 2024 S1, Q106 | C | Three strands of a beta-sheet of 4 peptides are hydrogen bonded with the orientation of the strands (parallel or antiparallel denoted by… |
| Jun 2024 S1, Q41 | B | In the representation of the di-peptide shown below, the superscript ‘-1’ denotes the atom of the previous amino acid while ‘+1’ denotes… |
| Jun 2024 S1, Q51 | B | Given below are Ramachandran plots for four different proteins. Choose the correct pair of proteins, both of which are predominantly alpha… |
| Jun 2024 S1, Q102 | C | Given below are four topology diagrams corresponding to different proteins. N and C denote the N- and C-terminal ends of the protein… |
| Jun 2024 S1, Q136 | C | In a protein stability study, three solutions, MolA (10 kDa) at 0.5 mM, MolB (20 kDa) at 0.5 mM, and MolC (20 kDa) at 1 mM, were subjected… |
| Jun 2024 S2, Q138 | C | Given below is a PONDR (Predictor of Natural Disordered Regions) score-plot versus the protein sequence. Based on the above figure, which… |
| Jun 2024 S2, Q141 | C | A decapeptide composed of MFTGPYCPRW was dissolved in 20 mM HEPES (pH 7.0), 50 mM NaCl, 50 mM Na2SO4, 5 mM DTT, and 4 mM EDTA. Which one of… |
| Dec 2023 S1, Q71 | C | The central rod domain of keratin protein is 300 amino acids in length. What is the approximate length (in Å) of the rod domain if the… |
| Dec 2023 S1, Q73 | C | The amino acid sequence of tetrapeptides (P, Q, R) is shown below. P) Asp-Gly-Asp-Ser Q) Gly-Ser-Arg-Gly R) Gly-Lys-Arg-Ala… |
| Dec 2023 S2, Q71 | C | If the length of a single continuous α-helical polypeptide is 108 Å, which one of the following statements is true? |
| Jun 2023 S2, Q72 | C | How long should it take the polypeptide backbone of a 6-residue, 10-residue, 15-residue and 20-residue folding nucleus to explore all its… |
| Jun 2023 S2, Q74 | C | The plot below has two curves (A, B) that show the fractional occupancy of hemoglobin and myoglobin by oxygen as a function of the amount… |
| Feb 2022 S1, Q24 | B | How many hydrogen bonds involving the backbone CO and NH can be observed in an α-helix consisting of 15 amino acid residues? |
| Feb 2022 S2, Q22 | B | What is the net charge of the peptide Tyr-Val-Arg at pH 5.0? The pKas of alpha amino and carboxyl groups are 9.6 and 2.3, respectively. The… |
| Feb 2022 S2, Q23 | B | Protein X is an all helical protein with 100 amino acids including 2 cysteines and a pI of 7.0. Which one of the following graphs best… |
| Feb 2022 S2, Q71 | C | Two experiments were performed on a peptide sample ‘X’. In experiment 1, treatment of ‘X’ with dithiothreitol (DTT), followed by blocking… |
| Feb 2022 S2, Q72 | C | The Ramachandran plot graphically shows which combination of torsional angles phi (φ) and psi (ψ) of amino acid residues contained in a… |
| Feb 2022 S2, Q74 | C | The pKa of the ionizable groups in the tripeptide shown below are indicated in the structure. The isoelectric point (pI) of this peptide is |
Enzymes – Catalysis & Kinetics (19 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q47 | B | In the catalytic triad of trypsin protease, serine forms a hydrogen bond with the histidine side chain. What will be the effect of this… |
| Jun 2025, Q139 | C | If 10 μg of pure carbonic anhydrase catalyzes the hydration of 0.30 g of CO2 in 1 min at 37°C at Vmax, what is the turnover number (kcat)… |
| Dec 2024 S1, Q72 | C | At what range of substrate concentration will an enzyme with a kcat of 30 s−1 and a Km of 0.005 M show one-quarter of its maximum rate? |
| Dec 2024 S1, Q83 | C | An enzyme has been found to efficiently catalyse the following reaction: Which one of the following parameters will be increased over the… |
| Dec 2024 S2, Q72 | C | The graph below shows the plot of 1/v vs 1/[S] for an enzymatic reaction, with the solid and dashed lines representing the reactions… |
| Jun 2024 S1, Q70 | B | Which one of the following pairs correctly matches the enzyme with its allosteric activator? |
| Jun 2024 S1, Q118 | C | A propionate kinase enzyme utilizes two substrates, propionate and acetate, with Km for propionate being half that of acetate. Which one of… |
| Jun 2024 S2, Q144 | C | An enzyme has a Km of 1 mM. Addition of different inhibitors changes Km and/or Vmax given as Kmapp and Vmaxapp (app for apparent)… |
| Dec 2023 S1, Q21 | B | Which one of the following enzymes does NOT catalyze the oxidation of substrate by reducing the electron acceptor, NAD+? |
| Dec 2023 S1, Q76 | C | What is the V0/Vmax ratio for an enzymatic reaction when [S] = 3 Km and 9 Km, respectively? |
| Dec 2023 S2, Q24 | B | An enzyme “X” converts a L-amino acid to a racemic mixture of D- and L- forms. Which one of the following coenzymes is utilized by enzyme X… |
| Jun 2023 S1, Q76 | C | Some properties of enzymes are listed in column X, and their kinetic expressions are listed in column Y. Which one of the following options… |
| Jun 2023 S2, Q73 | C | The enzyme-catalysed reaction shown below follows Michaelis-Menten kinetics. k1 = 1 × 108 M−1 s−1, k−1 = 4 × 104 s−1, k2 = 8 × 102 s−1 From… |
| Feb 2022 S1, Q21 | B | Following statements are made about uncompetitive inhibition of an enzyme: Which one of the following option represents the correct… |
| Feb 2022 S1, Q23 | B | The enzyme alkaline phosphatase was tested for its catalytic activity using the substrate para-nitrophenylphosphate. The KM obtained was 10… |
| Feb 2022 S1, Q71 | C | A schematic of a metabolic pathway is shown below. Under which of the following conditions would stoichiometric amounts of end products K… |
| Feb 2022 S1, Q72 | C | The following statements are being made to define the Michaelis constant (KM). It is: Which one of the following combination of statements is correct? |
| Feb 2022 S2, Q73 | C | Consider the following statements: Which one of the following options represents all correct statements? |
| Feb 2022 S2, Q75 | C | What is the fold difference between v at [S] = Km and v at [S] = 1000Km, where v is the initial velocity of an enzyme catalyzed reaction… |
Metabolism – Carbohydrates, Lipids, Amino Acids & Nucleotides (16 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q64 | B | The reactions of the urea cycle occur in two different cellular compartments and generate the following intermediates. Which… |
| Dec 2024 S1, Q29 | B | Which one of the following statements with regard to glyoxylate cycle is INCORRECT? |
| Dec 2024 S1, Q67 | B | Which one of the following statements is true regarding β-oxidation of fatty acids? |
| Dec 2024 S2, Q37 | B | Skeletal muscle cells need to convert pyruvate to lactate while sustaining anaerobic respiration to |
| Dec 2024 S2, Q83 | C | Given below are four metabolic intermediates (i-iv) listed against amino acids (A-E): Which one of the following options correctly pairs… |
| Jun 2024 S1, Q75 | C | Given below are a few statements regarding the rate of glycolysis, gluconeogenesis and glycogen metabolism. Which one of the following… |
| Jun 2024 S2, Q33 | B | Which one of the following compounds can serve as a direct acceptor of an additional amino group derived from amino acid catabolism? |
| Jun 2024 S2, Q89 | C | Following are the different critical reaction steps involved in the oxidation of lipids in many organisms. Choose the correct sequence of… |
| Dec 2023 S1, Q24 | B | Which one of the following pairs of metabolic intermediates does NOT provide a backbone carbon skeleton for the synthesis of amino acids? |
| Dec 2023 S1, Q74 | C | In a mammalian cell undergoing active glycolysis, what would be the effect of a sudden increase in the concentration of metabolites, AMP… |
| Jun 2023 S1, Q23 | B | In mature erythrocytes, the end-product of glycolysis that contains the carbons of glucose is: |
| Jun 2023 S1, Q74 | C | Aspartate (Asp) is an amino acid with the structure NH2-CH(CH2-COOH)-COOH. Given below are biosynthetic processes occurring in cells: Which… |
| Jun 2023 S1, Q75 | C | The following statements are made regarding conversion of pyruvate to acetyl-CoA going from glycolysis to citric acid cycle: Which one of… |
| Jun 2023 S2, Q76 | C | In yeast, under anaerobic conditions, pyruvate is fermented to ethanol through two steps: decarboxylation of pyruvate to acetaldehyde and… |
| Feb 2022 S2, Q21 | B | Phosphofructokinase catalyses one of the regulatory steps in glycolysis. Which one of the following metabolic changes leads to the… |
| Feb 2022 S2, Q76 | C | Purine and pyrimidine nucleotides serve as monomeric units of the nucleic acid polymers DNA and RNA. Mentioned below are some of the… |
Composition & Structure of Biomolecules (16 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q29 | B | Which one of the following statements about glycosaminoglycans (GAGs) is INCORRECT? |
| Jun 2025, Q89 | C | Given below are a few biological lipids (Column X) and their chemical nature (Column Y). Which one of the following options correctly… |
| Dec 2024 S1, Q139 | C | Cells have both reversible and non-reversible post-translational modifications. The following statements were made regarding the… |
| Dec 2024 S2, Q24 | B | Which one of the following bonds support the three intertwined polypeptide strands in the triple helical structure of collagen? |
| Dec 2024 S2, Q65 | B | The pKa of an amino acid side chain was measured in aqueous solution. Which one of the following is the correct arrangement of the amino… |
| Dec 2024 S2, Q142 | C | Below is a table with the list of post-translational modifications on proteins and amino acid residues that are correspondingly modified… |
| Jun 2024 S2, Q54 | B | Which one of the following statements regarding the stereoisomers of D-glucose is INCORRECT? |
| Jun 2024 S2, Q113 | C | A tree grows at 0.5 meter per day under optimal tropical conditions. Assuming the stem consists entirely of cellulose fibers, how many… |
| Dec 2023 S1, Q88 | C | The table below represents some protein modifications in Column X and their functions in Column Y. Which one of the following options… |
| Dec 2023 S1, Q145 | C | An oligopeptide is subjected to amino acid analysis and found to have the following composition. Tyr, Phe, Asp, Val, Arg, Met The following… |
| Dec 2023 S2, Q73 | C | Which one of the following options correctly depicts the stereo-conformation of the dipeptide derivative of Aspartic acid and Phenylalanine? |
| Jun 2023 S1, Q21 | B | Which one of the following sugars will not reduce Tollen’s reagent? |
| Jun 2023 S1, Q72 | C | A polypeptide was subjected to the following treatments with the indicated results. I. Acid hydrolysis: (1) (Ala, Arg, Cys, Glx, Gly, Lys… |
| Jun 2023 S1, Q73 | C | Consumption of untreated corn as the staple food causes the disease, pellagra. Pre-treatment of corn with Ca(OH)2 prevents this disease… |
| Jun 2023 S2, Q23 | B | Several proteins are modified by phosphorylation at specific amino acid residues to alter their activities. Which one of the following… |
| Jun 2023 S2, Q71 | C | The following statements are made with regard to the optical activity of amino acids derived from natural proteins: Which one of the… |
Nucleic Acid Conformation & Stability (13 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q53 | B | If 19% of the nucleotides in a genome are “A”, what percent are “C”, “G”, and “T”? |
| Dec 2024 S1, Q131 | C | Given below are two columns depicting structural features (Column X) and the DNA/RNA conformation (Column Y). Which one of the following… |
| Dec 2024 S2, Q128 | C | Match the following ribose sugar pucker in nucleic acids (labeled A, B, C, D) with their corresponding conformational states. The black… |
| Jun 2024 S1, Q83 | C | Which one of the following options represents a classical Hoogsteen base pairing? |
| Jun 2024 S2, Q40 | B | Which one of the following properties of grooves is a hallmark of the Z-form of DNA? |
| Jun 2024 S2, Q88 | C | The following four DNA oligos are mixed in equimolar concentration, heated to 95°C, and slowly annealed in a microcentrifuge tube. 5’ GCG… |
| Dec 2023 S1, Q23 | B | One strand of a palindromic dsDNA is composed of 5′-CCGCGGCGG-3′. Which one of the following forms of nucleic acid structures will be… |
| Dec 2023 S1, Q72 | C | Which one of the following nucleic acids with same concentrations in water, will form a stable stem-loop structure upon annealing by… |
| Dec 2023 S2, Q21 | B | The base composition of the genome of a newly identified virus is given below: Adenine: 25%; Cytosine: 35%; Guanine: 30%; Thymidine: 10%… |
| Dec 2023 S2, Q76 | C | The melting curves shown below are of two double-stranded DNA molecules of the same length. Which one of the following statements about… |
| Jun 2023 S2, Q21 | B | Which one of the following statements is TRUE? |
| Feb 2022 S2, Q24 | B | A. 5′- AGTAGTATCAACTATCATGA-3′ 3′- TCATCATAGTTGATAGTACT-5′ B. 5′- GACGTGCCAGGTGCGAGGTC-3′ 3′- CTGCACGGTCCACGCTCCAG-5′ C. 5′-… |
| Feb 2022 S2, Q29 | B | Heating of some nucleic acids shows an increase in the absorbance at 260 nm (A260) typified by the plot shown above. The sharp transition… |
Bioenergetics & Oxidative Phosphorylation (12 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q72 | C | Gastric juice (pH 1.5) is produced by pumping HCl from blood plasma (pH 7.4) into the stomach. Calculate the amount of free energy required… |
| Dec 2024 S1, Q56 | B | The citric acid cycle (TCA) operates only in the presence of molecular oxygen (O2). This is because |
| Dec 2024 S1, Q96 | C | If a 0.1 M solution of glucose 1-phosphate is incubated with a catalytic amount of phosphoglucomutase, the glucose 1-phosphate is… |
| Dec 2024 S2, Q75 | C | ΔG0 of a reaction shows the following temperature dependence. What is the expected dependence of Keq of the reaction on the temperature… |
| Jun 2024 S1, Q142 | C | For the coupled reaction given below, the equilibrium constants (K′eq) for equation [1] and equation [2] are 270 and 890, respectively… |
| Jun 2024 S2, Q24 | B | In which one the following, the proton motive force generated in mitochondrial electron transport is NOT used? |
| Dec 2023 S2, Q27 | B | Which one of the following statements about ATP generating mitochondria is TRUE? |
| Dec 2023 S2, Q74 | C | Given below are inhibitors of electron transport (Column X) and their target enzymes (Column Y) Which one of the following options… |
| Jun 2023 S1, Q24 | B | The standard free energy (kJ mol−1) of hydrolysis of glucose-1-phosphate is: |
| Jun 2023 S2, Q75 | C | Pyruvate generated by glycolysis, is converted to acetyl-coenzyme A, which is metabolized by the citric acid cycle generating energy-rich… |
| Feb 2022 S1, Q28 | B | Iron-sulphur clusters [Fe-S] are the key prosthetic groups that carry electrons in all of the below EXCEPT: |
| Feb 2022 S2, Q79 | C | Cyanide, a chemical warfare agent, is toxic because it: Choose the combination with all correct statements. |
Structure of Atoms, Molecules & Chemical Bonds (7 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q109 | C | A canonical Watson-Crick G:C base pair is stabilized by three hydrogen bonds formed between a donor (+0.25e) and acceptor (−0.35e) atom… |
| Dec 2024 S1, Q66 | B | Which one of the following types of interactions will be predominantly contributing to the stability of a nucleosome? |
| Jun 2024 S1, Q50 | B | Which one of the following statements regarding the structure of water molecule is correct? |
| Jun 2024 S2, Q110 | C | The surface electrostatic potential map of an 18 kDa protein is shown below. Shades of blue and red on the surface denote positively and… |
| Dec 2023 S2, Q22 | B | The amount of energy required to break a single covalent bond is: |
| Jun 2023 S1, Q22 | B | The solubility of NaCl is greater in water than ethanol. What physical property of the solvent governs this difference? |
| Jun 2023 S2, Q22 | B | In a hydrogen bond of the type D-H…A, where D-H is a weakly acidic donor group and A is a lone-pair-bearing acceptor atom, the D…A distance is |
Biophysical Chemistry – pH, Buffers & Equilibria (6 questions)
| Paper and question | Part | Question |
|---|---|---|
| Dec 2024 S2, Q104 | C | In a typical experiment, 15 mL of an aqueous solution containing an unknown quantity of acetylcholine had a pH of 7.65. When the solution… |
| Dec 2023 S1, Q22 | B | The pH of endocytic vesicles is 5.2, and the pH of gastric juice is 2.0. The endocytic vesicle has a [H+] that is |
| Jun 2023 S1, Q71 | C | What is the pH of a 10−7 M solution of HCl? |
| Jun 2023 S2, Q24 | B | One gram of a polysaccharide composed of 1000 glucose units has the same effect on osmolarity as that of |
| Feb 2022 S1, Q22 | B | Following are the pKa’s of the ionizable groups in lysine pKa1 = 2.16 (α – carboxylic group) pKa2 = 9.06 (α – amino group) pKa3 = 10.54 (ε… |
| Feb 2022 S1, Q75 | C | The pI of four proteins (A, B, C, D) are shown in the table below: To purify ‘D’ from a mixture of these four proteins in a single step… |
PYQs for every CSIR-NET unit
How to revise Biomolecules and Biochemistry with these questions
- Start with the two biggest subtopicsProtein Conformation & Stability and Enzymes – Catalysis & Kinetics are where most of the marks have been. Revise them first.
- Attempt before you readWork through a subtopic’s questions on paper, then check them against the answer keys.
- Find the repeatsThe same ideas keep coming back in new wording. When you get one wrong, look for its earlier version in the list above.
- Finish with a full paperTake a whole paper in live exam mode to practise choosing which Part C questions to attempt.
Keep going
<
p class=”lbq-src”>Source: CSIR-NET Life Sciences question papers and final answer keys, National Testing Agency, February 2022 to June 2025. Subtopic tags, difficulty ratings and solutions: Lesson Basket.
