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100+ Free NSEB Practice Questions

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2026 Statistics

Key Facts: NSEB Exam

60

Total Questions

IAPT

120 min

Exam Duration

IAPT

₹300

Registration Fee

IAPT

+3 / -1

Section A1 Marking

IAPT

Stage 1

Olympiad Level

HBCSE

Late Nov

Exam Date

IAPT

NSEB consists of 60 questions (48 single-correct, 12 multiple-correct) in 120 minutes. Scoring: +3/-1 (Section A1) and +6/0 (Section B1). Topics cover Cell Biology, Genetics, Human & Plant Physiology, Ecology, and Ethology. Registration fee is ₹300.

Sample NSEB Practice Questions

Try these sample questions to test your NSEB exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which of the following bonds stabilizes the primary structure of proteins?
A.Hydrogen bonds
B.Peptide bonds
C.Disulfide bonds
D.Ionic bonds
Explanation: The primary structure of a protein is the linear sequence of amino acids linked together. This sequence is stabilized solely by covalent peptide bonds formed between the carboxyl group of one amino acid and the amino group of another.
2A spherical cell has a radius of 2 micrometers. If its radius increases to 4 micrometers, how does its surface-area-to-volume ratio change?
A.It doubles
B.It remains unchanged
C.It is halved
D.It increases fourfold
Explanation: For a sphere, the surface area is 4*pi*r^2 and volume is (4/3)*pi*r^3, making the surface-area-to-volume (SA/V) ratio equal to 3/r. If the radius r increases from 2 micrometers to 4 micrometers, the ratio changes from 1.5 to 0.75, which is exactly halved.
3In an enzyme-catalyzed reaction, what is the effect of a competitive inhibitor on the Michaelis constant (Km) and the maximum velocity (Vmax)?
A.Km increases and Vmax decreases
B.Km increases and Vmax remains unchanged
C.Km remains unchanged and Vmax decreases
D.Km decreases and Vmax remains unchanged
Explanation: A competitive inhibitor binds to the active site of the enzyme, competing directly with the substrate. This increases the apparent Km because more substrate is needed to achieve half-maximum velocity, but Vmax remains unchanged because high substrate concentrations can outcompete the inhibitor.
4Which of the following cellular structures is responsible for the synthesis of lipids and the detoxification of drugs and poisons?
A.Rough endoplasmic reticulum
B.Smooth endoplasmic reticulum
C.Golgi apparatus
D.Lysosomes
Explanation: The smooth endoplasmic reticulum (SER) is lack of ribosomes and specializes in metabolic processes, including the synthesis of lipids (phospholipids and steroids), metabolism of carbohydrates, and detoxification of drugs and poisons, especially in liver cells.
5During glycolysis, which enzyme catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate?
A.Hexokinase
B.Phosphofructokinase-1
C.Aldolase
D.Pyruvate kinase
Explanation: Phosphofructokinase-1 (PFK-1) is the enzyme that transfers a phosphate group from ATP to fructose-6-phosphate, producing fructose-1,6-bisphosphate. This is a key rate-limiting and committed step of glycolysis that is highly regulated.
6Under anaerobic conditions, yeast cells regenerate NAD+ by converting pyruvate into which of the following compounds?
A.Lactate
B.Ethanol and carbon dioxide
C.Acetyl-CoA
D.Oxaloacetate
Explanation: In yeast, anaerobic respiration occurs via alcohol fermentation. Pyruvate is first decarboxylated to acetaldehyde (releasing CO2), which is then reduced to ethanol by alcohol dehydrogenase, oxidizing NADH back to NAD+ to allow glycolysis to continue.
7During the light reactions of photosynthesis, what is the primary function of photosystem II (PSII)?
A.To generate NADPH
B.To split water molecules and generate oxygen
C.To synthesize ATP directly via photophosphorylation
D.To fix carbon dioxide into sugars
Explanation: Photosystem II contains the reaction center P680. When it absorbs light, electrons are excited and transferred down an electron transport chain. The lost electrons are replaced by splitting water molecules (photolysis) at the oxygen-evolving complex, releasing protons and oxygen gas.
8Which of the following best describes the role of the Calvin cycle in C3 plants?
A.It uses ATP and NADPH to convert carbon dioxide into G3P
B.It splits water to release oxygen using solar energy
C.It converts pyruvate into acetyl-CoA under aerobic conditions
D.It generates ATP by moving protons down an electrochemical gradient
Explanation: The Calvin cycle takes place in the stroma of chloroplasts. It uses the chemical energy of ATP and the reducing power of NADPH (both produced during the light reactions) to fix atmospheric carbon dioxide into glyceraldehyde-3-phosphate (G3P), a three-carbon sugar.
9What is the thermodynamic significance of coupling endergonic reactions to ATP hydrolysis in biological systems?
A.It increases the activation energy of the endergonic reaction
B.It makes the overall free energy change (delta G) of the coupled reaction negative
C.It prevents the cells from reaching thermal equilibrium
D.It decreases the rate of the coupled reaction to maintain stability
Explanation: ATP hydrolysis is highly exergonic, with a negative change in Gibbs free energy (delta G). When coupled with an endergonic reaction (positive delta G), the sum of the free energy changes is negative, allowing the overall reaction to proceed spontaneously.
10Which of the following organelles contains its own DNA and ribosomally translates some of its own proteins?
A.Golgi apparatus
B.Lysosome
C.Mitochondrion
D.Peroxisome
Explanation: Mitochondria and chloroplasts contain circular DNA molecules, tRNA, and ribosomes that resemble prokaryotic machinery (endosymbiotic theory). They transcribe and translate a subset of their own structural proteins.

About the NSEB Exam

The National Standard Examination in Biology (NSEB) is the first stage of the selection process for the Indian National Biology Olympiad (INBO) and eventually the International Biology Olympiad (IBO). It is organized by the Indian Association of Physics Teachers (IAPT) in collaboration with the Association of Teachers in Biological Sciences (ATBS) and Homi Bhabha Centre for Science Education (HBCSE). The exam syllabus matches the CBSE senior secondary level (Class 11 & 12) biology curriculum, but the questions are designed to test deep conceptual comprehension, analytical skills, and experimental data interpretation rather than rote learning.

Questions

60 scored questions

Time Limit

120 minutes

Passing Score

MAS (50% of top 10 average)

Exam Fee

₹300 (Indian Association of Physics Teachers (IAPT))

NSEB Exam Content Outline

15-20%

Cell Biology & Biochemistry

Cell organelles, cellular membrane systems, cell cycle and division, biochemistry of proteins, lipids, carbohydrates, enzyme kinetics, and cellular metabolic respiration.

12-15%

Plant Anatomy and Physiology

Plant water relations, mineral nutrition, photosystems, light and dark reactions, respiration pathways, and the action of plant growth hormones.

20-25%

Animal Anatomy and Physiology

Mammalian physiological systems including digestion, cardiovascular dynamics, gas exchange mechanisms, osmoregulation, nerve impulse transmission, and endocrine control loops.

15-20%

Genetics, Molecular Biology & Evolution

Mendelian inheritance, non-Mendelian alleles, linkage maps, DNA structure, transcription, translation, prokaryotic and eukaryotic gene regulation, and mechanisms of evolutionary change.

10-12%

Ecology & Environment

Population dynamics, logistic and exponential growth, ecosystem thermodynamics, biogeochemical loops, community ecology, trophic interactions, and conservation biology.

10-15%

Biosystematics & Ethology

Taxonomy principles, character states, phylogenetic reconstruction, innate and learned animal behaviors, behavioral ecology, and social hierarchies.

How to Pass the NSEB Exam

What You Need to Know

  • Passing score: MAS (50% of top 10 average)
  • Exam length: 60 questions
  • Time limit: 120 minutes
  • Exam fee: ₹300

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

NSEB Study Tips from Top Performers

1Focus heavily on Campbell Biology to bridge the gap between standard NCERT facts and the analytical style of NSEB questions.
2Understand the mechanics of enzyme kinetics, cellular respiration, and biochemical pathways rather than just memorizing intermediate molecules.
3Practice inheritance problems, linkage calculations, and population genetics calculations (Hardy-Weinberg equilibrium) as they are common.
4Pay attention to Section B1 style questions, where checking multiple options requires complete clarity of the concepts.
5Solve previous years' NSEB papers under timed conditions to get used to the negative marking strategy in Section A1.

Frequently Asked Questions

What is the role of NSEB in the Biology Olympiad process?

NSEB is the first-stage (Stage 1) examination. Roughly the top 300 to 450 students nationwide qualify to write the Indian National Biology Olympiad (INBO) in Stage 2, which then narrows the pool further.

How is the passing score (MAS) determined?

The Minimum Admissible Score (MAS) is defined as 50% of the average score of the top 10 scoring candidates in the nation. To qualify for INBO, a student must meet the MAS, and then qualify based on proportional state quotas or nationwide merit.

What is the fee and scheduling for NSEB 2026?

The exam registration fee is ₹300 INR. Registrations are usually processed through recognized school centers between August and September, and the offline examination is scheduled for late November.

Are there negative marks in all sections of the NSEB exam?

No. In Section A1 (48 questions, single option correct), a wrong answer results in a deduction of 1 mark (+3 for correct). In Section B1 (12 questions, multiple options correct), there are no negative marks, but students only score the 6 marks if they identify all correct options.

Which books are recommended for preparing for the NSEB?

While NCERT textbooks for Class 11 and 12 Biology provide the framework, advanced books like 'Campbell Biology' (Reece et al.) and 'Genetics' (Snustad or Klug) are highly recommended to tackle Olympiad-level analytical questions.