UPSC CDS-2 Archives

1. ‘Altitude sickness’ is caused at high altitude due to

‘Altitude sickness’ is caused at high altitude due to

high partial pressure of oxygen

low partial pressure of oxygen

low level of haemoglobin

high partial pressure of carbon dioxide

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UPSC CDS-2 – 2016

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Altitude sickness is caused by exposure to low partial pressure of oxygen at high altitudes.

At higher altitudes, the atmospheric pressure is lower. This results in a lower partial pressure of oxygen, which reduces the amount of oxygen that can be taken up by the lungs and delivered to the body’s tissues, leading to hypoxia.

Symptoms of altitude sickness, also known as acute mountain sickness (AMS), can include headache, nausea, dizziness, fatigue, and shortness of breath. Severe forms include High Altitude Pulmonary Edema (HAPE) and High Altitude Cerebral Edema (HACE). Acclimatization is the process by which the body adjusts to the lower oxygen availability.

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2. Biological catalysts are protein molecules which 1. speed up a chemi

Biological catalysts are protein molecules which

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1. speed up a chemical reaction
2. remain unchanged after reaction
3. function optimally at 37 °C
4. do not have an enzymatic activity

Select the correct answer using the code given below.

1 only

1, 2 and 3

2 and 3 only

1, 3 and 4

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This question was previously asked in

UPSC CDS-2 – 2016

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Biological catalysts (enzymes) are protein molecules that speed up chemical reactions, remain unchanged after the reaction, and function optimally at around 37 °C (in the human body).

– Biological catalysts are enzymes, which are indeed protein molecules (with a few exceptions like catalytic RNA).
– Statement 1 is correct: Enzymes are catalysts, meaning they increase the rate of a chemical reaction without being consumed in the process.
– Statement 2 is correct: Like all catalysts, enzymes are not permanently altered or used up during the reaction and can be reused.
– Statement 3 is generally correct in the context of human enzymes: Many enzymes in the human body function optimally at physiological temperature, which is around 37 °C. However, the optimal temperature varies greatly among enzymes from different organisms (e.g., enzymes from thermophilic bacteria function at much higher temperatures). Assuming the question refers to typical biological contexts like the human body, this statement is considered correct.
– Statement 4 is incorrect: Biological catalysts *are* enzymes, and their activity *is* enzymatic activity. This statement directly contradicts the definition.
– Based on the statements, 1 and 2 are universally true for catalysts. Statement 3 is true for a common subset of biological catalysts (human enzymes). Statement 4 is false. The option including 1, 2, and 3 is the most fitting choice.

Enzymes are highly specific for the substrates they act upon and the reactions they catalyze. Their activity is influenced by factors such as temperature, pH, and the presence of inhibitors or activators.

3. Which of the following cells do not contain nucleus? 1. Root hair ce

Which of the following cells do not contain nucleus?

1. Root hair cells
2. Red blood cells
3. Platelets
4. Monocytes

Select the correct answer using the code given below.

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1 only

2 and 3 only

1, 2 and 4

2, 3 and 4

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This question was previously asked in

UPSC CDS-2 – 2016

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Mature red blood cells and platelets are cells/cell fragments in the human body that do not contain a nucleus.

– Statement 1: Root hair cells are specialized epidermal cells of plant roots involved in water and nutrient absorption. They are eukaryotic cells and *do* contain a nucleus, cytoplasm, and other organelles.
– Statement 2: Mature mammalian red blood cells (erythrocytes) are anucleated, meaning they lose their nucleus during maturation. This allows them to maximize the space available for hemoglobin, increasing oxygen-carrying capacity.
– Statement 3: Platelets (thrombocytes) are not complete cells but are small, irregular fragments of cytoplasm derived from megakaryocytes found in bone marrow. They lack a nucleus. They play a crucial role in blood clotting.
– Statement 4: Monocytes are a type of white blood cell (leukocyte) and are part of the immune system. They are large, mononuclear cells, meaning they *do* contain a prominent, often kidney-shaped or lobed nucleus.
– Therefore, among the given options, only red blood cells and platelets lack a nucleus.

The absence of a nucleus in mature red blood cells and platelets is a characteristic feature that distinguishes them from most other cells in the human body. This specialization enhances their specific functions (oxygen transport and blood clotting, respectively).

4. Which one of the following hormones is essential for the uptake of glu

Which one of the following hormones is essential for the uptake of glucose by cells in the human body?

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TSH

Insulin

Cortisol

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This question was previously asked in

UPSC CDS-2 – 2016

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Insulin is the hormone essential for the uptake of glucose by cells in the human body.

– Insulin is a hormone produced by the beta cells of the pancreas.
– Its primary role is to regulate blood glucose levels by facilitating the uptake of glucose from the bloodstream into most cells of the body, particularly muscle, fat, and liver cells.
– Insulin binds to receptors on cell membranes, triggering the translocation of glucose transporters (like GLUT4) to the cell surface, allowing glucose to enter the cell.
– GH (Growth Hormone) has effects on metabolism, including promoting growth and cell reproduction. It can increase blood glucose levels by stimulating gluconeogenesis and inhibiting glucose uptake.
– TSH (Thyroid Stimulating Hormone) stimulates the thyroid gland to produce thyroid hormones, which regulate metabolism but are not directly involved in glucose uptake by most cells.
– Cortisol is a glucocorticoid hormone produced by the adrenal glands. It also influences glucose metabolism, typically by increasing blood glucose levels (gluconeogenesis) and reducing peripheral glucose uptake.

Diabetes mellitus is a disease characterized by high blood glucose levels resulting from either insufficient insulin production (Type 1) or the body’s cells not responding properly to insulin (Type 2).

5. Which one of the following statements is not correct?

Which one of the following statements is not correct?

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The response of the ear to sound of increasing intensity is approximately logarithmic.

The sensitivity of the human ear does not vary with the frequency of sound.

When two or more waves traverse the same medium, the displacement of any element of the medium is the algebraic sum of the displacements due to each wave.

Longitudinal waves can travel in all media—solids, liquids and gases.

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UPSC CDS-2 – 2016

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The statement that the sensitivity of the human ear does not vary with the frequency of sound is not correct.

– Statement A is correct: The perceived loudness of sound is approximately logarithmic with respect to intensity, which is why the decibel scale (a logarithmic scale) is used.
– Statement B is incorrect: The human ear’s sensitivity is highly dependent on frequency. It is most sensitive to frequencies in the range of 2 kHz to 5 kHz and less sensitive to very low or very high frequencies within the audible range (typically 20 Hz to 20 kHz). This varying sensitivity is represented by equal-loudness contours (Fletcher-Munson curves or ISO 226 curves).
– Statement C is correct: The principle of superposition states that when multiple waves pass through the same medium, the net displacement at any point is the vector sum of the displacements caused by each individual wave. This applies to sound waves.
– Statement D is correct: Longitudinal waves, like sound waves, can travel through solids, liquids, and gases because these media can support compressions and rarefactions. Transverse waves, on the other hand, require a medium that can sustain shear forces, typically solids or the surface of liquids.

The variation in human hearing sensitivity with frequency is important in audio engineering and acoustics. For example, audio equalization is often used to adjust the frequency balance of sound to compensate for the ear’s non-uniform sensitivity.

6. Which one of the following physical quantities has the same dimensions

Which one of the following physical quantities has the same dimensions as that of Planck’s constant h?

Linear momentum

Angular momentum

Force

Potential energy

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This question was previously asked in

UPSC CDS-2 – 2016

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The physical quantity that has the same dimensions as Planck’s constant (h) is angular momentum.

– Planck’s constant (h) relates the energy (E) of a photon to its frequency (ν) by the equation E = hν. The dimensions of E are [ML²T⁻²] and the dimensions of ν are [T⁻¹]. Therefore, the dimensions of h are [E/ν] = [ML²T⁻²] / [T⁻¹] = [ML²T⁻¹].
– Let’s check the dimensions of the given options:
– Linear momentum (p = mv): [M] * [LT⁻¹] = [MLT⁻¹].
– Angular momentum (L = Iω or L = rp): [Moment of inertia * Angular velocity] or [Radius * Linear momentum]. Dimensions are [ML²] * [T⁻¹] or [L] * [MLT⁻¹] = [ML²T⁻¹].
– Force (F = ma): [M] * [LT⁻²] = [MLT⁻²].
– Potential energy (e.g., mgh): [M] * [LT⁻²] * [L] = [ML²T⁻²].
– Comparing the dimensions, angular momentum [ML²T⁻¹] has the same dimensions as Planck’s constant [ML²T⁻¹].

In quantum mechanics, angular momentum is quantized in units of Planck’s reduced constant (ħ = h/2π), which has the same dimensions as h. This dimensional equivalence is not a coincidence but reflects a fundamental connection between energy, frequency, and angular momentum in quantum physics.

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7. The pressure exerted by a 760 mm column of mercury at 0 °C is known a

The pressure exerted by a 760 mm column of mercury at 0 °C is known as

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1 pascal

1 atmosphere

1 bar

1 poise

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UPSC CDS-2 – 2016

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The pressure exerted by a 760 mm column of mercury at 0 °C under standard gravity is known as 1 atmosphere.

– Standard atmospheric pressure is defined as the pressure that supports a column of mercury exactly 760 millimeters (or 76 cm or 29.92 inches) high at 0 °C at sea level and standard gravitational acceleration.
– This pressure is internationally defined as 1 standard atmosphere (atm).
– 1 atm is equivalent to 101,325 Pascals (Pa), which is the SI unit of pressure.
– 1 bar is another unit of pressure, equal to 100,000 Pa, which is slightly less than 1 atm.
– Pascal is the SI unit of pressure (N/m²).
– Poise is a unit of dynamic viscosity.

The height of the mercury column is directly proportional to the atmospheric pressure, as demonstrated by Torricelli’s experiment. This measurement is used in barometers to indicate atmospheric pressure.

8. In a bipolar junction transistor

In a bipolar junction transistor

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all the three regions (the emitter, the base and the collector) have equal concentrations of impurity

the emitter has the least concentration of impurity

the collector has the least concentration of impurity

the base has the least concentration of impurity

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UPSC CDS-2 – 2016

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In a bipolar junction transistor (BJT), the base region has the least concentration of impurity.

– A BJT consists of three semiconductor regions: the emitter, the base, and the collector, separated by two p-n junctions.
– These regions are doped with impurities (donors or acceptors) to create n-type and p-type semiconductors.
– The doping levels are designed specifically for the transistor’s operation:
– Emitter: Heavily doped (high concentration) to efficiently inject charge carriers (electrons or holes) into the base.
– Base: Lightly doped (low concentration) and made very thin to allow most injected carriers from the emitter to reach the collector and to minimize recombination within the base.
– Collector: Moderately doped (intermediate concentration, less than emitter but more than base) and typically larger in size to collect the carriers from the base and dissipate heat.

The doping profile and physical geometry of the emitter, base, and collector regions are crucial for the performance of a bipolar junction transistor, determining its gain, operating speed, and power handling capabilities.

9. In the gamma decay of a nucleus

In the gamma decay of a nucleus

the mass number of the nucleus changes whereas its atomic number does not change

the mass number of the nucleus does not change whereas its atomic number changes

both the mass number and the atomic number of the nucleus change

neither the mass number nor the atomic number of the nucleus changes

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UPSC CDS-2 – 2016

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In the gamma decay of a nucleus, neither the mass number nor the atomic number of the nucleus changes.

– Gamma decay is a type of radioactive decay where an atomic nucleus in an excited state emits a gamma ray photon.
– A gamma ray is high-energy electromagnetic radiation and has no mass or charge.
– The emission of a gamma ray allows the nucleus to transition from a higher energy level to a lower energy level.
– Since no particles (protons or neutrons) are emitted or transformed, the number of protons (atomic number, Z) and the total number of nucleons (mass number, A) in the nucleus remains unchanged.
– Alpha decay decreases A by 4 and Z by 2. Beta decay increases Z by 1 (β⁻ decay) or decreases Z by 1 (β⁺ decay) while A remains unchanged.

Gamma decay often occurs after alpha or beta decay, when the daughter nucleus is left in an excited state. The excited nucleus de-excites by emitting one or more gamma rays.

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10. The spring constant of a spring depends on its

The spring constant of a spring depends on its

length only

material only

length and its diameter

thickness, its diameter and its material

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This question was previously asked in

UPSC CDS-2 – 2016

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The spring constant of a spring depends on its physical and material properties including its thickness, diameter, and material.

– The spring constant (k) quantifies the stiffness of a spring.
– For a helical spring, the spring constant is given by the formula k = (G * d⁴) / (8 * D³ * n), where G is the shear modulus of the material, d is the wire diameter (thickness), D is the coil diameter, and n is the number of active turns (related to length).
– Therefore, k depends on the material (shear modulus G), the wire thickness (d), the coil diameter (D), and the number of turns (n, which determines the overall length for a given coil diameter and pitch).
– Option D includes thickness (wire diameter), diameter (coil diameter), and material, which are the key determinants of the spring constant.

The spring constant is an intrinsic property of a specific spring configuration. Changing any of these physical parameters will change the spring constant. For example, a thicker wire makes the spring stiffer (higher k), a larger coil diameter or more turns make it less stiff (lower k), and using a material with a higher shear modulus makes it stiffer.

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