Life Sciences (XL) PYQs Feb 2020

Physiology Ecology and Evolution

An orange juice flowing at 0.80 kg s' enters a counter current double pipe heat exchanger at 20 °C and leaves at 72 °C.

This outcome reflects core biological organization, where structure-function relationships govern cellular processes. Option NAT captures this correctly because it integrates fundamental life science principles, consistent with textbook descriptions and experimental observations in general biology.

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

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Physiology Ecology and Evolution

The initial population of a bacterial strain increases from 1x10 ⁴ cells per mL to 1x10 ⁶ cells per mL in 120 minutes. T

This outcome reflects membrane organization, where lipid bilayer and protein trafficking maintain compartmentalization. Option NAT captures this correctly because it aligns with organelle function and transport, consistent with textbook descriptions and experimental observations in cell biology.

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

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Physiology Ecology and Evolution

The velocity of 2.2 gm diameter fat particles inside a centrifuge, running at 6000 rpm and 20 °C, is 0.25 mm s ⁻¹ . The

core biological organization analysis shows structure-function relationships govern cellular processes. Consequently Option NAT emerges as the valid choice since it integrates fundamental life science principles, aligning with established principles in general biology literature.

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

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Physiology Ecology and Evolution

In Drosophila, the red eye phenotype (W) is dominant over the recessive white eye mutant (w). In a mixed population of r

Evidence for Mendelian segregation indicates allele distribution and recombination generate phenotypic variation. Option NAT aligns with this, as it follows segregation and linkage principles, reflecting standard interpretations in genetics. This mechanism is extensively documented and reinforced by experimental data across multiple model systems and textbook discussions.

Ref: Griffiths et al., Introduction to Genetic Analysis, 11th Edition, Chapter 5, Linkage and Recombination, explains chromosomal mapping, crossing over, genetic distance and recombination frequencies underlying inheritance and variation.

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Microbiology Immunology and Biotechnology

continuous bacterial culture carried out in a chemostat is set to a flow rate of 40 ml/hr. The culture volume is equival

Evidence for microbial physiology indicates growth regulation and phage life cycles follow molecular programs. Option NAT aligns with this, as it corresponds to prokaryotic replication strategies, reflecting standard interpretations in microbiology.

Ref: Madigan et al., Brock Biology of Microorganisms, 15th Edition, Chapter 13, Virology and Bacteriophage Biology, explains viral replication, lytic and lysogenic cycles, virus-host interactions and molecular mechanisms of infection.

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Microbiology Immunology and Biotechnology

A 100 microl aliquot (10 ⁴ dilution) of the bacterial culture plated on the nutrient agar gave 4 colonies. The bacterial

Understanding membrane organization reveals lipid bilayer and protein trafficking maintain compartmentalization. Therefore Option NAT is correct because it aligns with organelle function and transport, which underpins key processes in cell biology.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 10, Membrane Structure and Transport, discusses lipid bilayer organization, membrane proteins, transporters and selective permeability providing foundation for cellular compartmentalization and signaling.

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Microbiology Immunology and Biotechnology

A bacterial culture has a generation time of 34 minutes. The time taken (in minutes, rounded off to two decimal places)

Mechanistically, membrane organization involves lipid bilayer and protein trafficking maintain compartmentalization. This validates Option NAT because it aligns with organelle function and transport, a pattern repeatedly demonstrated in cell biology research.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 10, Membrane Structure and Transport, discusses lipid bilayer organization, membrane proteins, transporters and selective permeability providing foundation for cellular compartmentalization and signaling.

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Microbiology Immunology and Biotechnology

A bacterial culture containing 3 x 10 ⁵ live cells was exposed to a newly developed sterilizing agent. After 30 minutes

The principle of membrane organization explains that lipid bilayer and protein trafficking maintain compartmentalization. Hence Option NAT fits best because it aligns with organelle function and transport, as documented in authoritative sources on cell biology.

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

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Cell Biology and Genetics

A 250 microl of bacteriophage stock containing 8x10 ⁸ phages/ml is added to 500111 of E. coli culture containing 4x10 ⁸

This outcome reflects microbial physiology, where growth regulation and phage life cycles follow molecular programs. Option NAT captures this correctly because it corresponds to prokaryotic replication strategies, consistent with textbook descriptions and experimental observations in microbiology.

Ref: Madigan et al., Brock Biology of Microorganisms, 15th Edition, Chapter 13, Virology and Bacteriophage Biology, explains viral replication, lytic and lysogenic cycles, virus-host interactions and molecular mechanisms of infection.

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Cell Biology and Genetics

A double homozygous mutant develops green and wrinkled seeds. When it was crossed with a true-breeding plant having yell

Understanding photosynthetic regulation reveals light harvesting and carbon fixation coordinate energy flow. Therefore Option NAT is correct because it supports efficient energy conversion, which underpins key processes in plant biology.

Ref: Taiz et al., Plant Physiology and Development, 6th Edition, Chapter 7, Photosynthesis and Carbon Assimilation, discusses light reactions, Calvin cycle, photorespiration and carbon fixation providing mechanistic insight into plant energy metabolism.

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Cell Biology and Genetics

An mRNA of a nuclear encoded plant gene, DSH ₂ O has an ORF of 1353 nucleotides. Provided that average molecular weight

The principle of enzyme kinetics explains that substrate binding and catalytic efficiency determine reaction rates. Hence Option NAT fits best because it reflects active-site specificity and regulation, as documented in authoritative sources on biochemistry.

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 of cellular energy metabolism.

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Biochemistry and Molecular Biology

The enzyme glucose isomerase catalyzes the inter-conversion of glucose and fructose as shown. Glucose Fructose The Δ G ᵒ

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: 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 of cellular energy metabolism.

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