UPSC CAPF Archives

21. Which one of the following statements is correct ?

Which one of the following statements is correct ?

Glucose breaks down to CO₂, H₂O and energy in all organisms

Glucose breaks down into ethanol, CO₂ and energy in our muscle cells

Glucose breaks down into CO₂, H₂O and energy in all aerobic tissues

Glucose breaks down into lactate and energy in yeast

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In aerobic respiration, which occurs in the presence of oxygen, glucose is completely broken down into carbon dioxide (CO₂), water (H₂O), and a large amount of energy (ATP). This process occurs in aerobic tissues of organisms, including humans. Option A is incorrect because not all organisms perform aerobic respiration (e.g., anaerobic bacteria, yeast under anaerobic conditions). Option B is incorrect because muscle cells produce lactate during anaerobic conditions, not ethanol and CO₂. Option D is incorrect because yeast produces ethanol and CO₂ during alcoholic fermentation, not lactate.

Aerobic respiration yields the maximum amount of energy from glucose and results in CO₂ and H₂O as final products. Anaerobic respiration (fermentation) yields less energy and produces different products like lactate or ethanol.

The overall equation for aerobic respiration is C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP). This process involves glycolysis (cytoplasm), the Krebs cycle (mitochondrial matrix), and the electron transport chain (inner mitochondrial membrane).

22. After fertilization, the ovule and ovary subsequently develop to form

After fertilization, the ovule and ovary subsequently develop to form

seed and fruit respectively

fruit and seed respectively

seed and flower respectively

degenerated ovule and seedless fruit respectively

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In flowering plants, following fertilization, the ovule develops into the seed, which contains the embryo and stored food. The ovary, which encloses the ovules, develops into the fruit, protecting the seed(s) and often aiding in their dispersal.

Fertilization triggers the post-fertilization changes in the flower, leading to the development of the fruit from the ovary and the seed(s) from the ovule(s).

The fruit wall is derived from the ovary wall and is called the pericarp. Different parts of the flower, such as the petals, sepals, and stamens, usually wither and fall off after fertilization.

23. In which part of the cell, the glucose is converted into pyruvate ?

In which part of the cell, the glucose is converted into pyruvate ?

Mitochondria

Nucleus

Cytoplasm

Endoplasmic reticulum

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The metabolic pathway in which glucose is converted into pyruvate is called glycolysis. This process occurs in the cytoplasm (cytosol) of the cell, both in prokaryotes and eukaryotes.

Glycolysis is the first stage of cellular respiration and occurs in the cytoplasm. It breaks down a molecule of glucose (a 6-carbon sugar) into two molecules of pyruvate (a 3-carbon molecule), producing a net gain of ATP and NADH.

Pyruvate then enters the mitochondria (in aerobic respiration) for further oxidation via the Krebs cycle and electron transport chain, or is converted to lactate or ethanol in anaerobic conditions (fermentation), also in the cytoplasm.

24. Which one of the following minerals is NOT a naturally occurring silic

Which one of the following minerals is NOT a naturally occurring silicate ?

Feldspar

Zeolite

Mica

Bauxite

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Bauxite is the principal ore of aluminium and is primarily composed of hydrated aluminium oxides and hydroxides, such as gibbsite, boehmite, and diaspore, often mixed with iron oxides, clay minerals, and quartz. It does not have the silicon-oxygen tetrahedral structure characteristic of silicate minerals. Feldspar, Zeolite, and Mica are all well-known families of naturally occurring silicate minerals.

Silicate minerals are composed of silicon and oxygen, often with other metals, forming structures based on the SiO₄⁴⁻ tetrahedron unit. Non-silicate minerals lack this fundamental structure.

Feldspars are tectosilicates, zeolites are porous tectosilicates, and micas are phyllosilicates (sheet silicates). Bauxite is classified as an oxide mineral.

25. Which one of the following is NOT a heterocyclic aromatic compound ?

Which one of the following is NOT a heterocyclic aromatic compound ?

Tropolone

Furan

Thiophene

Pyridine

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Tropolone is a seven-membered carbocyclic compound containing a ketone and a hydroxyl group. Its aromaticity arises from the cyclic conjugated system within the carbon ring, but the ring itself is made entirely of carbon atoms. Furan, Thiophene, and Pyridine are all five- or six-membered rings containing heteroatoms (Oxygen in Furan, Sulfur in Thiophene, Nitrogen in Pyridine) within the ring structure, along with conjugated pi systems that satisfy Hückel’s rule, making them heterocyclic aromatic compounds.

A heterocyclic compound contains at least one atom other than carbon (such as O, N, S) in its ring structure. An aromatic compound is cyclic, planar, conjugated, and obeys Hückel’s rule (4n+2 pi electrons).

Tropolone is a carbocyclic aromatic compound. Common examples of heterocyclic aromatic compounds include pyridine, furan, thiophene, pyrrole, and imidazole.

26. Which one of the following is the average atomic mass of chlorine atom

Which one of the following is the average atomic mass of chlorine atom ?

35.9 u

35.5 u

35.0 u

37.0 u

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The average atomic mass of chlorine atom is approximately 35.5 u.

Chlorine occurs naturally as a mixture of two main isotopes: chlorine-35 (³⁵Cl) and chlorine-37 (³⁷Cl). Their approximate natural abundances are about 75% for ³⁵Cl (mass ≈ 34.97 u) and 25% for ³⁷Cl (mass ≈ 36.97 u). The average atomic mass is a weighted average of the masses of its isotopes based on their natural abundance.

Average atomic mass = (0.75 × 34.97 u) + (0.25 × 36.97 u) ≈ 26.23 u + 9.24 u ≈ 35.47 u, which is rounded to 35.5 u.

27. Which one of the following statements on photoelectric effect is NOT c

Which one of the following statements on photoelectric effect is NOT correct ?

”Albert

”For

”At

”The

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The statement “At a frequency v > v₀, the kinetic energy of ejected electrons does not change on increasing the frequency of incident light” is NOT correct.

According to Einstein’s explanation of the photoelectric effect, the maximum kinetic energy (KE_max) of the ejected electrons is given by KE_max = h(v – v₀), where h is Planck’s constant, v is the frequency of incident light, and v₀ is the threshold frequency. This equation shows that for v > v₀, the maximum kinetic energy is directly proportional to the frequency of the incident light; increasing v leads to increased KE_max.

Statement A is correct; Einstein received the Nobel Prize in Physics in 1921 for his explanation of the photoelectric effect. Statement B is correct; a minimum frequency (threshold frequency) is required for electron emission. Statement D is correct; the number of emitted electrons is proportional to the intensity of the incident light (for v > v₀), as higher intensity means more photons striking the surface.

28. Latent heat corresponds to the change in heat at constant

Latent heat corresponds to the change in heat at constant

temperature only

volume only

pressure only

temperature, volume and pressure

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Latent heat corresponds to the change in heat required for a substance to undergo a phase transition (like melting, boiling, or condensation) at a constant temperature.

During a phase change at constant pressure, the temperature remains constant while heat energy is absorbed (for melting/boiling/sublimation) or released (for freezing/condensation/deposition). This energy is used to change the state (break or form intermolecular bonds) rather than increase the kinetic energy of the molecules, which would result in a temperature change.

For typical phase transitions under standard conditions, pressure is also constant. However, the defining characteristic of latent heat is that it is the energy involved in a phase change *without* a change in temperature. Volume typically changes during a phase transition.

29. At triple point the substance co-exists in 1. Liquid phase 2. Solid

At triple point the substance co-exists in

1. Liquid phase
2. Solid phase
3. Vapour phase

Select the correct answer using the code given below :

1 only

1 and 2 only

2 and 3 only

1, 2 and 3

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At the triple point of a substance, the solid, liquid, and vapour (gaseous) phases of that substance coexist in thermodynamic equilibrium.

The triple point is a unique specific temperature and pressure for a substance, distinct from the melting point (solid-liquid equilibrium) or boiling point (liquid-vapour equilibrium) which vary with pressure.

For water, the triple point is at 0.01°C (273.16 K) and 611.657 pascals (about 0.006 atm). This specific point is used to define the Kelvin temperature scale.

30. Oil and water do NOT mix because of the property of

Oil and water do NOT mix because of the property of

bulk modulus

shear strain

volume effect

surface tension

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Oil and water do not mix due to the property of surface tension (more specifically, interfacial tension between the two liquids).

Water is a polar molecule with strong hydrogen bonds, giving it high surface tension. Oil is nonpolar with weaker intermolecular forces. They have different cohesive forces and weak adhesive forces between them, causing them to minimize contact area. This tendency to minimize interfacial area is a manifestation of interfacial tension, which is related to the surface tensions of the individual liquids and their interactions.

Bulk modulus is a measure of resistance to uniform compression. Shear strain is a measure of deformation under shear stress. Volume effect is not a standard term in this context.