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General Science and Technology

222 questions

All types222Multiple choice117Multiple select40True / False8Matching44Ordering13
Question 1Question →

Infectious human diseases are caused by various types of pathogens, including bacteria, viruses, and protozoa. Which of the following diseases is caused by a bacterial infection?

Show answer & explanation

Answer: Cholera

Answer

Cholera is the disease caused by a bacterial pathogen (Vibrio cholerae).
The option specifying Cholera is correct because Cholera is caused by Vibrio cholerae, a flagellated bacterium transmitted primarily through water contaminated with human fecal matter.

Step-by-Step Solution

1
Identify the causative agent of Cholera
Cholera is caused by the bacterium Vibrio cholerae.
Vibrio cholerae is a comma-shaped bacterium that causes severe watery diarrhea and dehydration.
2
Analyze the nature of the remaining disease pathogens
Influenza and Measles are caused by viruses, while Sleeping Sickness is caused by a protozoan parasite.
Categorizing each pathogen confirms that only Cholera is bacterial.

Key Concept

Classification of Infectious Human Diseases by Pathogen Type
Estimated Time:45s
Question 2Question →

Consider the following statements regarding statutory cybersecurity agencies and digital authentication frameworks in India:

1. The Indian Computer Emergency Response Team (CERT-In) is designated under Section 70B of the Information Technology Act, 2000 as the national nodal agency for computer security incident response.
2. Under the Information Technology Act, 2000, an Electronic Signature is strictly restricted to asymmetric cryptosystems and hash functions, whereas a Digital Signature is a broader, technology-neutral legal concept.
3. The Cyber Swachhta Kendra (Botnet Cleaning and Malware Analysis Centre) is operated by CERT-In to assist in detecting botnet infections and providing remediation tools to citizens.

Which of the statements given above is/are correct?

Show answer & explanation

Answer: 1 and 3 only

Answer

1 and 3 only
The statement identifying CERT-In's mandate under Section 70B of the IT Act, 2000 is accurate. Furthermore, Cyber Swachhta Kendra is indeed operated by CERT-In to sanitize infected systems. However, the legal definition of Electronic Signature is technology-neutral, while Digital Signature specifically uses asymmetric cryptography, making the second statement incorrect.

Step-by-Step Solution

1
Evaluate Statement 1 regarding CERT-In designation.
Statement 1 is correct.
Section 70B of the Information Technology (IT) Act, 2000 explicitly designates CERT-In as the national nodal agency for cybersecurity incident response, monitoring, and issuing emergency alerts.
2
Evaluate Statement 2 regarding Digital vs Electronic Signatures under the IT Act.
Statement 2 is incorrect.
The IT Act, 2000 defines a Digital Signature as a specific authentication technique based on asymmetric cryptosystems and hash functions (Public Key Infrastructure). The 2008 Amendment introduced 'Electronic Signature' as a broader, technology-neutral term encompassing digital signatures, e-KYC based signatures, and other prescribed electronic authentication methods.
3
Evaluate Statement 3 regarding Cyber Swachhta Kendra.
Statement 3 is correct.
Cyber Swachhta Kendra is the Botnet Cleaning and Malware Analysis Centre operated by CERT-In under the Ministry of Electronics and Information Technology (MeitY) to analyze malware and provide free botnet removal tools.

Key Concept

Statutory Cybersecurity Governance and Digital Authentication Standards
Estimated Time:2m 0s
Question 3Question →

With reference to agricultural chemicals and fertilizers widely used in industrial applications and soil management, consider the following statements:

1. Biuret (C2H5N3O2C_2H_5N_3O_2) is an undesirable byproduct formed during high-temperature thermal condensation of urea, which acts as a potent phytotoxin to germination and seedling roots if present above permissible limits.
2. Single Superphosphate (SSP) is industrially manufactured by treating insoluble fluoroapatite rock phosphate with concentrated nitric acid to produce water-soluble monocalcium phosphate.
3. Calcium Ammonium Nitrate (CAN) is an eco-friendly nitrogenous fertilizer that is chemically neutral, making it safe for continuous application on both acidic and alkaline soils without altering soil pH.

Which of the statements given above are correct?

Show answer & explanation

Answer: 1 and 3 only

Answer

The correct option is the one stating that statements 1 and 3 only are correct.
Biuret is indeed a thermal byproduct of urea that damages crops when excessive, and Calcium Ammonium Nitrate (CAN) is chemically engineered with calcium carbonate to function as a neutral fertilizer without disturbing soil pH. Single Superphosphate requires sulfuric acid rather than nitric acid.

Step-by-Step Solution

1
Analyze Statement 1 regarding Biuret toxicity in Urea manufacturing.
Statement 1 is correct.
During the industrial prilling and granulation of urea (CO(NH2)2CO(NH_2)_2), two molecules of urea combine at elevated temperatures (>130°C) with the loss of ammonia to form biuret (NH2−CO−NH−CO−NH2NH_2-CO-NH-CO-NH_2). High biuret content causes foliar burn and phytotoxicity in plants.
2
Analyze Statement 2 regarding Single Superphosphate (SSP) synthesis.
Statement 2 is incorrect.
Single Superphosphate (SSP) is manufactured by reacting pulverized rock phosphate (Ca3(PO4)2Ca_3(PO_4)_2 or apatite) with concentrated sulfuric acid (H2SO4H_2SO_4). The reaction yields water-soluble monocalcium phosphate [Ca(H2PO4)2Ca(H_2PO_4)_2] and insoluble calcium sulfate (gypsum, CaSO4CaSO_4). Reacting with nitric acid produces nitrophosphate, not SSP.
3
Analyze Statement 3 regarding Calcium Ammonium Nitrate (CAN) properties.
Statement 3 is correct.
Calcium Ammonium Nitrate (CAN) is prepared by mixing ammonium nitrate with powdered limestone/calcium carbonate (CaCO3CaCO_3). Because straight ammonium nitrate is acid-forming, the addition of limestone neutralizes the residual acidity, making CAN a popular neutral fertilizer suitable for diverse soil types.

Key Concept

Industrial Fertilizer Chemistry, Biuret Phytotoxicity, Acidulation of Rock Phosphate, and Soil Neutral Fertilizers
Question 4Question →

With reference to plant physiology, cellular transport mechanisms, and modern agricultural biotechnology, which of the following statements are correct?

Select all that apply

Show answer & explanation

Answer: Agrobacterium tumefaciens utilizes T-DNA transfer via a type IV secretion system to integrate specific genetic material into host plant nuclear genomes, serving as a primary vector in crop genetic engineering.; Abscisic acid (ABA) induces stomatal closure under drought stress by activating efflux anion channels in guard cell membranes, leading to potassium ion loss and reduced turgor pressure.

Answer

The correct statements are the one describing Agrobacterium tumefaciens genetic transformation and the one explaining Abscisic acid-mediated stomatal closure during water stress.
The statements regarding Agrobacterium tumefaciens T-DNA insertion and Abscisic acid (ABA)-induced stomatal closure are correct. Agrobacterium utilizes a bacterial type IV secretion apparatus encoded by Vir proteins to insert recombinant T-DNA into plant nuclei. ABA serves as the key plant stress hormone, opening guard cell anion channels to lose potassium ions and turgor pressure, thereby conserving water.

Step-by-Step Solution

1
Evaluate the statement on Agrobacterium tumefaciens genetic transfer mechanisms.
Agrobacterium tumefaciens transfers T-DNA from its Ti plasmid into host plant chromosomes using a vir-gene encoded type IV secretion system. This statement is scientifically accurate.
Agrobacterium is widely recognized as Nature's genetic engineer for recombinant plant technology.
2
Analyze the nitrogen-fixing bacteria classification statement.
Azotobacter (aerobic) and Clostridium (anaerobic) are free-living bio-fertilizer microbes, not nodule-forming endosymbionts like Rhizobium. This statement is incorrect.
Distinguishing free-living nitrogen fixers from symbiotic bacteroid associations is essential in soil microbiology.
3
Examine the physiological pathway of ABA-induced stomatal regulation.
Abscisic acid binds guard cell receptors, triggering intracellular calcium spikes, activating SLAC1 anion channels, causing mass efflux of K⁺ and osmotic water exit. This statement is scientifically accurate.
ABA is the primary stress phytohormone preventing transpirational water loss.
4
Assess the source, transport direction, and physiological role of cytokinins versus auxins.
Polar basipetal transport and apical dominance suppression of lateral buds are signature characteristics of auxins, not cytokinins. This statement is incorrect.
Cytokinins counteract apical dominance and promote lateral shoot growth.

Key Concept

Plant Hormone Signaling, Bio-fertilizer Microorganisms, and Recombinant Agrobacterium Vector Technology
Estimated Time:1m 30s
Question 5Question →

Match the chemical compounds listed in Column I with their corresponding primary commercial or daily life applications in Column II:

Click a left item, then click its matching right item

Items

Plaster of Paris
Sodium Thiosulfate (Hypo)
Silicon Carbide (Carborundum)
Magnesium Hydroxide

Matches

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Answer

Plaster of Paris matches with orthopedic casts and decorative moldings; Sodium Thiosulfate matches with photographic fixing; Silicon Carbide matches with industrial abrasives; and Magnesium Hydroxide matches with antacid suspension.
The correct pairings match each compound to its specific role: Plaster of Paris is standard for orthopedic casts due to its exothermic hardening; Sodium Thiosulfate complexes silver halides during photographic fixation; Silicon Carbide functions as an abrasive due to extreme hardness; and Magnesium Hydroxide neutralizes excess stomach acid as Milk of Magnesia.

Step-by-Step Solution

1
Identify the industrial setting property and use of Plaster of Paris.
Plaster of Paris (CaSO4⋅12H2OCaSO_4 \cdot \frac{1}{2}H_2O) hydrates to form gypsum (CaSO4⋅2H2OCaSO_4 \cdot 2H_2O), expanding slightly and setting into a rigid shape used for bone immobilization and statue casting.
Hydration and rapid recrystallization provide structural rigidity.
2
Determine the chemical function of Sodium Thiosulfate (Hypo).
Sodium thiosulfate removes light-sensitive, unreacted AgBrAgBr from photographic emulsions by complexation: AgBr+2Na2S2O3→Na3[Ag(S2O3)2]+NaBrAgBr + 2Na_2S_2O_3 \rightarrow Na_3[Ag(S_2O_3)_2] + NaBr.
Fixing is necessary to prevent the unexposed film from darkening on subsequent light exposure.
3
Analyze the mechanical and structural application of Silicon Carbide.
Silicon carbide (SiCSiC) is a covalent lattice solid with high thermal conductivity and hardness, making it a standard industrial abrasive for grinding wheels and refractory materials.
Strong directional Si−CSi-C covalent bonds give it hardness approaching diamond.
4
Examine the pharmaceutical application of Magnesium Hydroxide.
Magnesium hydroxide acts as a non-absorbable antacid reacting with gastric acid via Mg(OH)2+2HCl→MgCl2+2H2OMg(OH)_2 + 2HCl \rightarrow MgCl_2 + 2H_2O.
Its low hydroxyl ion concentration in aqueous suspension makes it non-corrosive yet effective for neutralizing acid.

Key Concept

Applications of inorganic compounds in daily life, medicine, photography, and manufacturing
Estimated Time:1m 15s
Question 6Question →

In industrial boiler operations and domestic water treatment, the presence of dissolved calcium and magnesium salts leads to boiler scale formation and reduced detergent efficiency. Which of the following chemical compounds is commercially known as 'Calgon' and softens hard water by forming soluble complex anions with calcium and magnesium ions?

Show answer & explanation

Answer: Sodium hexametaphosphate

Answer

Sodium hexametaphosphate is commercially known as Calgon and removes water hardness by sequestering calcium and magnesium ions into soluble complex anions.
Sodium hexametaphosphate (Na6P6O18Na_6P_6O_{18}) is commercially designated as Calgon. In aqueous solution, it ionizes to release [Na4P6O18]2−[Na_4P_6O_{18}]^{2-} complex anions, which bind Ca2+Ca^{2+} and Mg2+Mg^{2+} ions to form highly soluble complex salts such as [Na2CaP6O18]2−[Na_2CaP_6O_{18}]^{2-} and [Na2MgP6O18]2−[Na_2MgP_6O_{18}]^{2-}, preventing scale deposition in industrial boilers and improving lathering in cleaning applications.

Step-by-Step Solution

1
Identify the trade name and chemical identity
The commercial trade name 'Calgon' stands for 'calcium gone', which chemically corresponds to sodium hexametaphosphate, (NaPO3)6(NaPO_3)_6 or Na6P6O18Na_6P_6O_{18}.
Matching common industrial trade names to precise chemical nomenclature is a standard requirement in applied chemistry.
2
Analyze the chemical mechanism of water softening
When sodium hexametaphosphate is added to hard water, it dissociates as: Na6P6O18→2Na++[Na4P6O18]2−Na_6P_6O_{18} \rightarrow 2Na^+ + [Na_4P_6O_{18}]^{2-}. The complex anion exchanges sodium for calcium or magnesium: [Na4P6O18]2−+Ca2+→[Na2CaP6O18]2−+2Na+[Na_4P_6O_{18}]^{2-} + Ca^{2+} \rightarrow [Na_2CaP_6O_{18}]^{2-} + 2Na^+.
The sequestered calcium ions remain locked inside the soluble complex anion, preventing them from precipitating out as scale or forming insoluble scum with soaps.
3
Differentiate from alternative water treatment chemicals
Washing soda causes precipitation, alum causes coagulation of suspended particles, and bleaching powder is a disinfectant.
Distinguishing between precipitation, coagulation, disinfection, and complex ion sequestration confirms the unique role of Calgon.

Key Concept

Calgon Process and Complex Ion Formation in Water Softening
Estimated Time:1m 0s
Question 7Question →

Consider the following statements regarding the fundamental properties of the genetic code in molecular biology:

1. The genetic code is degenerate, meaning that a single amino acid can be specified by more than one codon.
2. The codon AUG possesses a dual function, coding for the amino acid methionine as well as acting as the initiator codon.
3. The genetic code is ambiguous, meaning that a particular triplet codon can code for several different amino acids depending on cellular conditions.

Which of the statements given above is/are correct?

Show answer & explanation

Answer: 1 and 2 only

Answer

1 and 2 only
The combination '1 and 2 only' is correct because the genetic code exhibits degeneracy (61 sense codons coding for 20 amino acids) and AUG serves a dual role as both an initiator codon and the codon for methionine. In contrast, the genetic code is non-ambiguous because each codon specifies precisely one amino acid.

Step-by-Step Solution

1
Evaluate statement 1 regarding genetic code degeneracy.
Statement 1 is correct.
There are 64 codons and only 20 standard amino acids. Most amino acids are coded by more than one triplet codon (for example, leucine and arginine are specified by six different codons each), which defines the degenerate nature of the genetic code.
2
Evaluate statement 2 regarding the functions of the AUG codon.
Statement 2 is correct.
AUG acts as the universal start codon that initiates translation in polypeptide synthesis, and it also incorporates the amino acid methionine into the growing polypeptide chain.
3
Evaluate statement 3 regarding the specificity and unambiguity of the genetic code.
Statement 3 is incorrect.
The genetic code is unambiguous and specific, meaning that one specific codon codes for one and only one amino acid. It is never ambiguous.
4
Synthesize the evaluations to select the matching statement combination.
Only statements 1 and 2 are correct.
Combining the valid statements yields '1 and 2 only'.

Key Concept

Properties of the Genetic Code: Degeneracy, Unambiguity, and Initiation Codons
Question 8Question →

Match the genetic phenomena listed in List-I with their correct biological descriptions in List-II:

Click a left item, then click its matching right item

Items

Pleiotropy
Epistasis
Polygenic Inheritance
Codominance

Matches

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Answer

Pleiotropy corresponds to a single gene influencing multiple phenotypic traits; Epistasis corresponds to one gene masking or altering the expression of another gene; Polygenic Inheritance corresponds to a quantitative trait controlled by multiple additive genes; Codominance corresponds to equal and simultaneous expression of both alleles in a heterozygote.
Each genetic phenomenon is accurately matched to its definition: Pleiotropy denotes a single gene governing multiple phenotypic features; Epistasis describes masking interactions between different gene loci; Polygenic inheritance describes multiple genes combining additively for a single trait; and Codominance describes the distinct, unblended expression of both heterozygous alleles.

Step-by-Step Solution

1
Define Pleiotropy and connect to its mechanism
Matched with the description of a single gene controlling multiple phenotypic effects
Pleiotropy represents the multi-trait manifestation of a single mutation or gene locus.
2
Differentiate Epistasis from standard allelic dominance
Matched with the description where one gene modifies or masks the expression of another independent gene
Epistasis involves non-allelic gene interaction across different loci.
3
Analyze Polygenic Inheritance
Matched with the cumulative additive effect of multiple genes creating continuous variation
Polygenic traits are metric traits governed by numerous loci.
4
Identify Codominance
Matched with equal and simultaneous phenotypic expression of both alleles in a heterozygote
Codominance differs from incomplete dominance because neither allele is recessive or blended.

Key Concept

Non-Mendelian Genetic Interactions and Inheritance Patterns
Estimated Time:1m 15s
Question 9Question →

During gametogenesis in a diploid organism, non-disjunction of a homologous chromosome pair occurs during Anaphase I of meiosis. Assuming normal segregation in Meiosis II, which of the following chromosome distributions will be observed in the four resulting gametes?

Show answer & explanation

Answer: Two gametes with n+1n + 1 chromosomes and two gametes with n−1n - 1 chromosomes

Answer

Two gametes with n+1n + 1 chromosomes and two gametes with n−1n - 1 chromosomes
When non-disjunction takes place in Anaphase I of meiosis, the failure of homologous chromosomes to segregate properly yields one daughter cell with an extra chromosome and another daughter cell missing that chromosome. When these cells undergo normal Meiosis II, the resulting four gametes consist of two (n+1)(n + 1) gametes and two (n−1)(n - 1) gametes, leading to complete aneuploidy among all four products.

Step-by-Step Solution

1
Analyze the meiotic stage and event specified in the scenario
Non-disjunction occurs at Anaphase I, meaning a homologous chromosome pair fails to separate to opposite poles.
Meiosis I is the reductional division where homologous pairs segregate.
2
Determine the chromosomal content of the two intermediate secondary gametocytes after Meiosis I
One secondary cell receives both homologous chromosomes (an extra chromosome, n+1n + 1), while the other cell receives neither (lacking a chromosome, n−1n - 1).
The entire pair moves to one daughter cell instead of dividing equally.
3
Trace the chromosome distribution through normal Meiosis II equational division
The (n+1)(n + 1) cell divides sister chromatids into two (n+1)(n + 1) gametes, and the (n−1)(n - 1) cell divides into two (n−1)(n - 1) gametes.
Meiosis II separates sister chromatids normally, generating two (n+1)(n + 1) and two (n−1)(n - 1) gametes from the four total products.

Key Concept

Meiotic Non-Disjunction and Aneuploidy Formation
Estimated Time:1m 0s
Question 10Question →

Chemical substances are extensively utilized in water purification, industrial refrigeration, and safety equipment. Which of the following statements regarding the applications and behaviors of these chemical compounds are correct?

Select all that apply

Show answer & explanation

Answer: Bleaching powder (CaOCl2\text{CaOCl}_2) acts as an effective disinfectant in municipal water treatment through the liberation of available chlorine.; Solid carbon dioxide (CO2\text{CO}_2), known as dry ice, sublimes directly from solid to gas at atmospheric pressure, making it a coolant that leaves no liquid residue.

Answer

The statements confirming that bleaching powder acts as a disinfectant through the release of active chlorine and that solid carbon dioxide functions as a residue-free coolant via sublimation are correct.
Bleaching powder serves as an established germicidal disinfectant by generating active hypochlorite and chlorine species in aqueous solution, while solid carbon dioxide (dry ice) sublimes cleanly into vapor under standard conditions, providing cryogenic cooling without liquid byproduct.

Step-by-Step Solution

1
Evaluate the mechanism of bleaching powder in water treatment
Bleaching powder (CaOCl2\text{CaOCl}_2) reacts in water to release active chlorine, which oxidizes organic matter and sterilizes water supplies.
Chlorine chemistry is fundamental to municipal disinfection protocols.
2
Examine the role of potash alum versus water softening methods
Potash alum (K2SO4⋅Al2(SO4)3⋅24H2O\text{K}_2\text{SO}_4\cdot\text{Al}_2(\text{SO}_4)_3\cdot 24\text{H}_2\text{O}) provides Al3+\text{Al}^{3+} cations that destabilize colloidal suspensions (coagulation/flocculation), but it does not remove dissolved permanent hardness ions like zeolites or ion-exchange resins do.
Distinguishing water clarification from chemical softening prevents functional misattribution.
3
Assess the physical behavior and utility of dry ice
Solid CO2\text{CO}_2 undergoes direct sublimation into gaseous carbon dioxide at atmospheric pressure without melting, preserving packaging integrity during perishable transport.
Thermodynamic phase change properties determine its industrial refrigeration use.
4
Analyze the gas composition in fire extinguishing equipment
Carbon monoxide (CO\text{CO}) is a toxic, flammable gas (2CO+O2→2CO2\text{2CO} + \text{O}_2 \rightarrow \text{2CO}_2) and cannot suppress fires; carbon dioxide (CO2\text{CO}_2) or dry chemical agents are used instead.
Safety compounds must be non-combustible and non-toxic during deployment.

Key Concept

Chemical principles and industrial applications of disinfectants, coagulants, sublimating refrigerants, and non-combustible gases
Estimated Time:1m 0s
Question 11Question →

Match the clean and renewable energy technologies in List-I with their corresponding fundamental operational principles or key structural features in List-II:

Click a left item, then click its matching right item

Items

Pyrolysis (Thermochemical Conversion)
Solar Power Tower (CSP)
Proton Exchange Membrane Fuel Cell (PEMFC)
Oscillating Water Column (OWC)

Matches

Show answer & explanation

Answer

Pyrolysis matches thermal decomposition of biomass without oxygen; Solar Power Tower matches heliostats focusing sunlight onto a central molten salt receiver; Proton Exchange Membrane Fuel Cell matches electrochemical reaction across a solid polymer membrane at low temperature; Oscillating Water Column matches trapped air driving a bidirectional Wells turbine.
Each clean energy technology is correctly paired with its defining operational principle: Pyrolysis corresponds to anaerobic thermal decomposition of organic biomass; Solar Power Tower corresponds to heliostat sun-tracking concentrating solar rays onto a central molten salt receiver; PEMFC corresponds to low-temperature electrochemical conversion across a solid polymer membrane; and Oscillating Water Column corresponds to ocean wave pneumatic pressure driving a Wells turbine.

Step-by-Step Solution

1
Analyze Pyrolysis (Thermochemical Conversion)
Pyrolysis is defined by high-heat biomass breakdown under oxygen-deprived conditions to generate bio-char, bio-oil, and combustible gas mixtures.
Differentiates thermochemical pyrolysis from gasification (partial oxidation) or anaerobic digestion (biological breakdown).
2
Analyze Solar Power Tower (Concentrated Solar Power)
Solar towers utilize fields of dual-axis tracking mirrors called heliostats to concentrate sunlight onto an elevated central thermal receiver.
Distinguishes point-focus power towers from line-focus parabolic trough solar collector systems.
3
Analyze Proton Exchange Membrane Fuel Cell (PEMFC)
PEMFC technology utilizes a solid polymer membrane electrolyte operating under low-temperature conditions (60∘C−80∘C60^\circ\text{C}-80^\circ\text{C}) to convert hydrogen and oxygen into electricity.
Distinguishes polymer membrane cells from high-temperature Solid Oxide Fuel Cells (SOFC) or Molten Carbonate Fuel Cells (MCFC).
4
Analyze Oscillating Water Column (OWC)
OWC devices capture wave energy by compressing an enclosed air column to rotate a self-rectifying Wells turbine.
Distinguishes wave-action OWC devices from tidal barrages or ocean thermal energy conversion (OTEC) systems.

Key Concept

Working principles and technological classifications of renewable energy systems and clean technology devices
Question 12Question →

In evolutionary cell biology, mitochondria and chloroplasts are classified as semi-autonomous organelles that originated through endosymbiotic events. Which of the following statements correctly describe the structural and genetic characteristics supporting their endosymbiotic evolutionary origin? (Select all correct options)

Select all that apply

Show answer & explanation

Answer: Both organelles contain their own circular, double-stranded DNA molecules that are naked and devoid of extensive histone protein complexes, resembling bacterial genomes.; Both organelles contain 70S ribosomes within their internal compartments that are sensitive to antibacterial antibiotics such as chloramphenicol.

Answer

The statements highlighting circular histone-free DNA genomes and bacterial-type 70S ribosomes sensitive to antibiotics are correct.
The correct statements correctly identify the core molecular evidence supporting the Endosymbiotic Theory: mitochondria and chloroplasts maintain circular, histone-free DNA genomes analogous to prokaryotes, and possess 70S ribosomes whose protein synthesis is susceptible to bacterial antibiotic inhibitors.

Step-by-Step Solution

1
Analyze genomic organization of semi-autonomous organelles
Mitochondria and chloroplasts harbor prokaryotic-like circular DNA without histone proteins.
Endosymbiotic origin from ancestral alpha-proteobacteria and cyanobacteria preserved circular genome topology.
2
Evaluate translational machinery characteristics
Organellar ribosomes are 70S (composed of 50S and 30S subunits), inhibited by prokaryotic translation inhibitors like chloramphenicol.
Eukaryotic cytosolic ribosomes are 80S, demonstrating the distinct bacterial lineage of organellar translation systems.
3
Assess degree of genetic autonomy and division mechanism
Both organelles depend on imported nuclear proteins and divide independently by binary fission rather than mitotic spindle partitioning.
Endosymbiotic gene transfer to the host nucleus rendered these organelles semi-autonomous rather than completely autonomous.

Key Concept

Endosymbiotic Theory and Characteristics of Semi-Autonomous Organelles
Estimated Time:1m 15s
Question 13Question →

Consider the following statements regarding biological nitrogen fixation in legume root nodules:

1. The enzyme nitrogenase, which reduces atmospheric nitrogen (N2N_2) to ammonia (NH3NH_3), is irreversibly inactivated in the presence of molecular oxygen.
2. Leghaemoglobin acts as an oxygen scavenger that regulates free oxygen concentration inside root nodules to protect nitrogenase while sustaining bacteroid cellular respiration.

Which of the statements given above is/are correct?

Show answer & explanation

Answer: Both 1 and 2

Answer

Both statements 1 and 2 are correct.
Both statements are correct. The nitrogenase enzyme requires strictly microaerophilic or anaerobic conditions because molecular oxygen causes irreversible damage to its iron-sulfur clusters. To solve this oxygen paradox, legumes synthesize leghaemoglobin (the globin protein produced by the plant host and heme group by the bacterial symbiont), which buffers free oxygen concentrations at extremely low levels while maintaining a steady flux to bacteroid mitochondria.

Step-by-Step Solution

1
Analyze Statement 1 regarding Nitrogenase enzyme sensitivity.
Nitrogenase contains iron-molybdenum protein complexes that undergo rapid denaturation when exposed to free molecular oxygen (O2O_2), making anaerobic conditions mandatory for its activity.
Verify biochemical properties of the nitrogen-fixing enzyme.
2
Analyze Statement 2 regarding Leghaemoglobin functionality.
Leghaemoglobin has a very high affinity for oxygen. It binds free oxygen in the nodule cytoplasm, keeping oxygen partial pressure extremely low to safeguard nitrogenase, while efficiently delivering bound oxygen to Rhizobium bacteroids for ATP generation via oxidative phosphorylation.
Verify physiological mechanism of the oxygen carrier protein in root nodules.
3
Synthesize the correctness of both statements.
Both Statement 1 and Statement 2 accurately describe essential requirements and adaptations for symbiotic nitrogen fixation.
Select the option that confirms both statements.

Key Concept

Symbiotic Nitrogen Fixation and Oxygen Paradox in Root Nodules
Question 14Question →

In eukaryotic cells, proteins destined for secretion follow a strictly coordinated endomembrane pathway from their initial synthesis to extracellular release. Arrange the following stages of the secretory pathway in the correct chronological order from start to finish.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological order begins with translation and translocation into the rough endoplasmic reticulum, followed by vesicular transfer to the cis-Golgi, modification across the Golgi cisternae, packaging into secretory vesicles at the trans-Golgi network, and ends with exocytosis at the plasma membrane.
In eukaryotic cells, the secretory pathway operates in a strict unidirectional sequence: nascent proteins are translocated into the rough endoplasmic reticulum lumen, exported in transport vesicles to the cis-Golgi network, processed through the Golgi cisternae to the trans-Golgi network, pinched off into secretory vesicles, and released externally via plasma membrane exocytosis.

Step-by-Step Solution

1
Identify the primary site of entry into the endomembrane system
The polypeptide chain is synthesized by ribosomes and translocated into the lumen of the rough endoplasmic reticulum.
Secretory proteins contain an N-terminal signal sequence directing them to the rough endoplasmic reticulum before any downstream transport can occur.
2
Trace vesicular transfer to the first receiving compartment of the Golgi complex
Transport vesicles bud from the endoplasmic reticulum and fuse with the cis-Golgi network.
The endoplasmic reticulum serves as the initial quality-control station before cargo moves anterograde to the cis-face of the Golgi.
3
Track maturation and biochemical modification through the Golgi stack
Proteins undergo sequential post-translational modifications as they traverse from cis- to trans-Golgi cisternae.
Enzymes in successive Golgi cisternae modify oligosaccharide chains and tag molecules for proper sorting.
4
Identify post-Golgi vesicle formation
Secretory vesicles bud off from the trans-Golgi network.
The trans-Golgi network acts as the major dispatch center packaging proteins into dedicated post-Golgi transport vesicles.
5
Identify the terminal export event at the cell boundary
Secretory vesicles fuse with the plasma membrane during exocytosis to discharge their cargo.
Exocytosis delivers the mature protein into the extracellular fluid while incorporating vesicle lipids into the plasma membrane.

Key Concept

Eukaryotic Endomembrane Secretory Pathway
Estimated Time:1m 15s
Question 15Question →

During semi-conservative DNA replication in living cells, the progressive unwinding of the double helix produces significant positive supercoiling and torsional strain ahead of the advancing replication fork. Which of the following enzymes is primarily responsible for relieving this torsional tension by making transient cuts in the DNA backbone?

Show answer & explanation

Answer: DNA Topoisomerase

Answer

DNA Topoisomerase is the enzyme responsible for relieving torsional strain and supercoiling ahead of the replication fork.
DNA Topoisomerases are critical isomerase enzymes that regulate the overwinding or underwinding of DNA. During replication, as DNA helicase separates the twin strands, torsional tension builds up ahead of the fork. Topoisomerase cuts the phosphate backbone of either one strand (Type I) or both strands (Type II), allows the strained helix to swivel and release tension, and then religates the severed bonds.

Step-by-Step Solution

1
Identify the cellular problem described at the replication fork
As the DNA duplex unwinds rapidly during replication, severe topological overwinding (positive supercoiling) accumulates in the DNA helix ahead of the replication fork.
Understanding the physical mechanics of double-helical separation helps identify which specific enzymatic activity is required.
2
Distinguish the specific functions of the enzymes involved in DNA replication
DNA Helicase unwinds the double helix, RNA Primase synthesizes starting primers, DNA Polymerase elongates daughter strands, DNA Ligase seals fragments, and DNA Topoisomerase manages helical topological strain.
Each replication enzyme possesses distinct catalytic specificity.
3
Select the enzyme that specifically alters DNA topology
DNA Topoisomerase introduces transient single-strand or double-strand cuts to release rotational stress and subsequently religates the phosphodiester backbone.
Topoisomerase activity prevents replication fork stalling caused by excessive twisting forces.

Key Concept

Enzymatic machinery of DNA replication and regulation of DNA topology
Estimated Time:1m 0s
Question 16Question →

Match List-I (Everyday Physical Phenomenon) with List-II (Underlying Physics Principle) and select the correct match:

Click a left item, then click its matching right item

Items

Formation of mirage in hot deserts
Spherical shape of small falling raindrops
Blue appearance of the clear daytime sky
Operation of hydraulic brakes in automobiles

Matches

Show answer & explanation

Answer

Formation of mirage matches with Total Internal Reflection; Spherical shape of raindrops matches with Surface Tension; Blue sky appearance matches with Rayleigh Scattering; Hydraulic brakes operation matches with Pascal's Law.
Each everyday phenomenon directly corresponds to its core physical law: mirages result from total internal reflection in stratified air temperatures, raindrops assume a minimal surface area sphere due to surface tension, the blue sky is produced by Rayleigh scattering of shorter light wavelengths, and hydraulic brakes transmit force via Pascal's law of fluid pressure.

Step-by-Step Solution

1
Identify the cause of desert mirages
Total Internal Reflection
Superheated air near the ground creates a steep refractive index gradient, causing light to undergo total internal reflection.
2
Identify why raindrops are spherical
Surface Tension
Surface tension forces liquid surfaces to contract into the minimal surface area configuration, which is a sphere.
3
Identify the mechanism behind the sky's blue color
Rayleigh Scattering
Rayleigh scattering intensity is inversely proportional to the fourth power of wavelength, causing shorter blue wavelengths to scatter widely.
4
Identify the principle governing hydraulic brakes
Pascal's Law
Pascal's law governs fluid pressure transmission in confined systems, allowing force amplification in hydraulic brakes.

Key Concept

Everyday Applications of Optics, Surface Phenomena, and Fluid Mechanics
Question 17Question →

The apparent twinkling of stars when observed from the surface of the Earth during nighttime is primarily caused by which of the following optical phenomena?

Show answer & explanation

Answer: Atmospheric refraction of starlight due to varying refractive indices of air layers

Answer

Atmospheric refraction of starlight due to varying refractive indices of air layers
As starlight passes through the Earth's atmosphere, it encounters continuously changing air temperatures and densities, causing the light rays to continuously refract (bend). Because stars act as point sources of light from immense distances, these rapid fluctuations in light paths cause the apparent position and brightness of the star to fluctuate, creating the twinkling effect.

Step-by-Step Solution

1
Identify the cause of density variations in the Earth's atmosphere
Air temperature and density fluctuate continuously across different atmospheric layers, leading to fluctuating refractive indices.
Light travels at slightly different speeds through air of varying density and temperature.
2
Analyze how starlight behaves as it enters and travels through these fluctuating layers
The path of starlight undergoes continuous refractive bending as it travels toward the observer.
Continuous change in refractive index causes atmospheric refraction.
3
Relate the refractive bending to the visual observation from Earth
The apparent position and brightness of the point-source star fluctuate rapidly, producing the twinkling effect.
Because stars are distant point sources, small variations in light path noticeably shift light intensity reaching the eye.

Key Concept

Atmospheric Refraction
Question 18Question →

Match the endocrine glands listed in List-I with their primary secreted hormones listed in List-II:

Click a left item, then click its matching right item

Items

Pancreas
Thyroid Gland
Adrenal Gland
Pituitary Gland

Matches

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Answer

Pancreas matches with Insulin, Thyroid Gland matches with Thyroxine, Adrenal Gland matches with Adrenaline, and Pituitary Gland matches with Growth Hormone.
The correct mapping pairs each gland with its principal endocrine secretion: Pancreas pairs with Insulin, Thyroid Gland pairs with Thyroxine, Adrenal Gland pairs with Adrenaline, and Pituitary Gland pairs with Growth Hormone.

Step-by-Step Solution

1
Identify the primary hormone secreted by the Pancreas.
The Pancreas secretes Insulin.
Insulin is produced by pancreatic beta cells to manage blood sugar.
2
Identify the primary hormone secreted by the Thyroid Gland.
The Thyroid Gland secretes Thyroxine.
Thyroxine regulates body metabolism.
3
Identify the primary hormone secreted by the Adrenal Gland.
The Adrenal Gland secretes Adrenaline.
Adrenaline is responsible for emergency stress reactions.
4
Identify the primary hormone secreted by the Pituitary Gland.
The Pituitary Gland secretes Growth Hormone.
Growth Hormone targets tissues across the body to promote growth.

Key Concept

Human Endocrine System and Hormonal Functions
Question 19Question →

Match the physical applications and everyday observations in List-I with their underlying governing physics principles in List-II, and select the correct matching order.

Click a left item, then click its matching right item

Items

Curved trajectory of a rapidly spinning ball through air during flight
Accelerated rate of cooling of hot liquid when poured into a wide saucer
Voltage transformation between isolated electrical circuits in a power transformer
High-frequency ultrasonic acoustic wave emission from a driven quartz crystal

Matches

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Answer

The curved flight of a spinning ball matches the pressure gradient from velocity variation (Magnus Effect); the accelerated cooling of liquid in a saucer matches enhanced heat loss via increased evaporative surface area; voltage step in a transformer matches EMF generation from varying magnetic flux (Faraday's Law); and ultrasonic wave emission from quartz matches lattice deformation under electrical fields (Piezoelectric Effect).
Each everyday observation maps precisely to its fundamental physical principle: spinning ball motion maps to fluid pressure gradients (Magnus Effect), liquid cooling in saucers maps to surface area dependence of evaporation, transformer operation maps to magnetic flux induction (Faraday's Law), and quartz ultrasonic generation maps to electromechanical crystal lattice distortion (Piezoelectric Effect).

Step-by-Step Solution

1
Analyze fluid dynamics of spinning bodies in motion
The air velocity relative to the ball surface is higher on one side than the other, yielding a pressure differential perpendicular to the motion axis (Magnus Effect).
Explains why spinning sports balls curve in flight.
2
Analyze thermodynamic energy transfer across phase boundaries
Evaporation rate scales directly with exposed surface area, increasing latent heat loss.
Explains why spreading a liquid over a broader area accelerates cooling.
3
Analyze electromagnetic energy transfer mechanisms
Time-varying current induces time-varying magnetic flux, which induces electromotive force in nearby coils via Faraday's Law.
Underpins contactless voltage stepping in electrical power transformers.
4
Analyze electromechanical transduction in crystalline materials
Electric potential applied across non-centrosymmetric crystals generates cyclic physical strains producing ultrasonic vibrations.
Underpins ultrasonic pulse generation using quartz transducers.

Key Concept

Interdisciplinary principles of fluid dynamics, thermodynamics, electromagnetism, and solid-state acoustics in daily technology and natural phenomena
Question 20Question →

Surface tension is an important property of liquids observed in daily life. Which of the following everyday phenomena are directly caused by surface tension? Select all the correct statements.

Select all that apply

Show answer & explanation

Answer: Raindrops acquiring a spherical shape as they fall; Small insects like water striders walking across the surface of a pond

Answer

Raindrops forming spherical shapes and water striders walking on water surfaces are both direct manifestations of liquid surface tension.
Raindrops acquiring a spherical shape and small insects walking on water are both direct manifestations of surface tension. Cohesive forces draw surface liquid molecules inward, giving droplets a minimal surface area shape (a sphere) and creating a tensile film strong enough to support small insects.

Step-by-Step Solution

1
Define surface tension and identify its physical characteristics.
Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible owing to cohesive forces among molecules.
Understanding the fundamental cause of surface tension helps evaluate its everyday effects.
2
Evaluate the choices related to fluid behavior.
A sphere has the minimum surface area for a given volume, so falling raindrops become spherical. Cohesive forces also create a surface layer that supports light objects such as water striders.
Both behaviors minimize surface energy and demonstrate surface tension.
3
Evaluate optical choices.
The apparent bending of objects in water and road mirages are optical phenomena driven by light refraction and total internal reflection.
These effects depend on light propagation speeds through different media, not cohesive liquid forces.

Key Concept

Surface tension in liquids due to intermolecular cohesive forces
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