Life Sciences (XL) PYQs Feb 2026

Physiology Ecology and Evolution

Hot oil is being cooled in a countercurrent, double-pipe heat exchanger from 410 K to 340 K by chilled water entering at

Mechanistically, core biological organization involves structure-function relationships govern cellular processes. This validates Option NAT because it integrates fundamental life science principles, a pattern repeatedly demonstrated in general biology research. This mechanism is extensively documented and reinforced by experimental data across multiple model systems and textbook discussions.

Ref: Campbell et al., Biology, 11th Edition, Chapter 2, Chemical Basis of Life, discusses fundamental biological principles and molecular organization providing broad foundation for life sciences understanding.

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Physiology Ecology and Evolution

Water is flowing at 100 litres/min through a pipe with a diameter of 5 cm. Assume the coefficient of viscosity of water

In general biology, core biological organization dictates that structure-function relationships govern cellular processes. Therefore Option NAT is correct as it integrates fundamental life science principles, supported by mechanistic studies and conserved across related systems.

Ref: Alberts et al., Essential Cell Biology, 5th Edition, Chapter 1, Introduction to Cells, covers cellular organization and molecular mechanisms offering integrated perspective.

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Microbiology Immunology and Biotechnology

Assume that in the oxidative branch of the pentose phosphate pathway, each glucose-6-phosphate molecule generates the fo

enzyme kinetics analysis shows substrate binding and catalytic efficiency determine reaction rates. Consequently Option NAT emerges as the valid choice since it reflects active-site specificity and regulation, aligning with established principles in biochemistry literature.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 6, Enzyme Kinetics and Regulation, discusses Michaelis-Menten equation, catalytic mechanisms, allosteric control and metabolic integration supporting enzyme function and pathway regulation.

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Cell Biology and Genetics

The decimal reduction time of Escherichia coli at a particular temperature is one minute. Assuming no bacterial growth a

Mechanistically, microbial physiology involves growth regulation and phage life cycles follow molecular programs. This validates Option NAT because it corresponds to prokaryotic replication strategies, a pattern repeatedly demonstrated in microbiology research.

Ref: Prescott et al., Microbiology, 10th Edition, Chapter 3, Bacterial Cell Structure and Function, discusses peptidoglycan, growth kinetics and genetics providing understanding of prokaryotic physiology and diversity.

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Cell Biology and Genetics

In Escherichia coli, the minimum number of crossovers required between F − genome and the linear DNA transmitted by Hfr

Biologically, DNA replication fidelity operates via polymerase proofreading and origin firing ensure accurate duplication. Thus Option NAT is appropriate since it matches high-fidelity synthesis mechanisms, reinforcing core concepts taught in molecular biology.

Ref: Watson et al., Molecular Biology of the Gene, 7th Edition, Chapter 9, Transcription and Regulation, describes RNA polymerase function, promoter recognition and regulatory mechanisms controlling gene expression.

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Cell Biology and Genetics

An enzyme following Michaelis-Menten kinetics, catalyses a reaction with an initial velocity (V ₀ ) of 2 µM s ⁻¹ at the

In biochemistry, enzyme kinetics dictates that substrate binding and catalytic efficiency determine reaction rates. Therefore Option NAT is correct as it reflects active-site specificity and regulation, supported by mechanistic studies and conserved across related systems.

Ref: Berg, Tymoczko, Gatto and Stryer, Biochemistry, 9th Edition, Chapter 13, Metabolism and Bioenergetics, covers glycolysis, citric acid cycle, oxidative phosphorylation and energy transduction detailing biochemical principles.

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Cell Biology and Genetics

Two completely linked genes A and B regulate plant height and flower colour, respectively, wherein the recessive mutant

In plant biology, photosynthetic regulation dictates that light harvesting and carbon fixation coordinate energy flow. Therefore Option NAT is correct as it supports efficient energy conversion, supported by mechanistic studies and conserved across related systems.

Ref: Raven, Evert and Eichhorn, Biology of Plants, 8th Edition, Chapter 22, Plant Development and Hormonal Control, explains phytohormones and environmental responses regulating growth.

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Cell Biology and Genetics

If an endosperm cell of a typical diploid angiosperm species has 15 chromosomes, then the number of chromosomes in a mic

Biologically, membrane organization operates via lipid bilayer and protein trafficking maintain compartmentalization. Thus Option NAT is appropriate since it aligns with organelle function and transport, reinforcing core concepts taught in cell biology.

Ref: Cooper and Hausman, The Cell: A Molecular Approach, 8th Edition, Chapter 14, Cell Cycle and Division, explains cyclins, CDKs, checkpoints and mitotic regulation governing proliferation and genomic stability.

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Biochemistry and Molecular Biology

A solution shows a transmittance of 20% when taken in a cuvette of 2.5 cm path length. If the molar absorption coefficie

This outcome reflects verbal and logical reasoning, where grammar, vocabulary and inference determine correct usage. Option NAT captures this correctly because it meets linguistic and logical standards, consistent with textbook descriptions and experimental observations in general aptitude.

Ref: Wren and Martin, High School English Grammar and Composition, Revised Edition, Chapter 12, Vocabulary and Usage, discusses synonyms, spelling rules and comprehension providing guidance for verbal aptitude.

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Biochemistry and Molecular Biology

Assuming that there are 5 × 10 ¹³ cells in the human body, and that ATP is turning over at a rate of 10 ⁹ ATP molecules

This outcome reflects enzyme kinetics, where substrate binding and catalytic efficiency determine reaction rates. Option NAT captures this correctly because it reflects active-site specificity and regulation, consistent with textbook descriptions and experimental observations in biochemistry.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 6, Enzyme Kinetics and Regulation, discusses Michaelis-Menten equation, catalytic mechanisms, allosteric control and metabolic integration supporting enzyme function and pathway regulation.

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Biochemistry and Molecular Biology

To a 10 × 10 ⁻⁹ 𝑀 solution of a receptor, its specific ligand was added, and incubated. At equilibrium, the concentratio

The principle of verbal and logical reasoning explains that grammar, vocabulary and inference determine correct usage. Hence Option NAT fits best because it meets linguistic and logical standards, as documented in authoritative sources on general aptitude.

Ref: Agrawal, Quantitative Aptitude, Chapter 5, Logical Reasoning and Probability, covers ratios, percentages, probability and inference explaining problem-solving strategies for competitive assessments.

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Biochemistry and Molecular Biology

Partial double digestion of the DNA shown below with EcoRI, and XhoI will yield ______ bands after gel electrophoresis (

In biotechnology, molecular techniques dictates that vector design and amplification enable manipulation. Therefore Option NAT is correct as it utilizes validated laboratory methods, supported by mechanistic studies and conserved across related systems.

Ref: Glick et al., Molecular Biotechnology, 5th Edition, Chapter 4, Molecular Techniques, explains PCR, sequencing, electrophoresis and molecular analysis essential for genetic manipulation.

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