UPSC CDS-2 Archives

1. Which one of the following statements about starch and glycogen is cor

Which one of the following statements about starch and glycogen is correct ?

Both starch and glycogen are found in plant cells.

Both starch and glycogen are found in animal cells.

Starch is present in plant cells and glycogen is present in animal cells.

Both starch and glycogen are present in plant cells as well as animal cells.

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Starch and glycogen are polysaccharides that serve as energy storage molecules in living organisms. Their occurrence differs between plant and animal cells.

– Starch is the primary storage carbohydrate in plants. It is stored in plastids (like chloroplasts and amyloplasts) and is the main form of carbohydrate consumed by humans from plant sources (e.g., grains, potatoes).
– Glycogen is the primary storage carbohydrate in animals and fungi. In animals, it is primarily stored in the liver and muscles, where it can be quickly mobilized to provide glucose for energy.
Therefore, starch is characteristic of plant cells, while glycogen is characteristic of animal cells.

Both starch and glycogen are polymers of glucose. Starch is a mixture of amylose (unbranched) and amylopectin (branched), while glycogen is more highly branched than amylopectin, allowing for rapid glucose release.

2. In plant cells

In plant cells

Nucleus does not need a membrane but chloroplasts are surrounded by their own membrane.

Nucleus and chloroplasts are surrounded separately by their own membrane.

Nucleus is surrounded by membrane but chloroplasts do not need membrane.

Both nucleus and chloroplasts are not surrounded by any membrane.

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Plant cells, like most eukaryotic cells, contain various membrane-bound organelles. The question asks about the membranes surrounding the nucleus and chloroplasts.

– The nucleus in plant cells is a prominent organelle enclosed by a double membrane known as the nuclear envelope.
– Chloroplasts, the sites of photosynthesis in plant cells, are also enclosed by a double membrane.
Therefore, both the nucleus and chloroplasts are surrounded separately by their own membranes.

Other double-membraned organelles in eukaryotic cells include mitochondria. Single-membraned organelles include the endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles. Ribosomes are not membrane-bound organelles.

3. Cl$^{-}$ is not isoelectronic with

Cl$^{-}$ is not isoelectronic with

K$^{+}$

Mg$^{2+}$

S$^{2-}$

P$^{3-}$

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Isoelectronic species are atoms or ions that have the same number of electrons. Cl$^{-}$ has an atomic number of 17, so Cl has 17 electrons. Cl$^{-}$ has gained one electron, giving it 17 + 1 = 18 electrons. We need to find the species among the options that does not have 18 electrons.

– K$^{+}$: Atomic number of K is 19. K$^{+}$ has lost one electron, so it has 19 – 1 = 18 electrons.
– Mg$^{2+}$: Atomic number of Mg is 12. Mg$^{2+}$ has lost two electrons, so it has 12 – 2 = 10 electrons.
– S$^{2-}$: Atomic number of S is 16. S$^{2-}$ has gained two electrons, so it has 16 + 2 = 18 electrons.
– P$^{3-}$: Atomic number of P is 15. P$^{3-}$ has gained three electrons, so it has 15 + 3 = 18 electrons.
Thus, Cl$^{-}$ (18 electrons) is not isoelectronic with Mg$^{2+}$ (10 electrons).

Other common isoelectronic series with 18 electrons include Ar, Ca$^{2+}$, Sc$^{3+}$. The electronic configuration for all species with 18 electrons is 1s²2s²2p⁶3s²3p⁶, which is the electron configuration of the noble gas Argon.

4. Consider the following statements about Tincture of Iodine : 1. It i

Consider the following statements about Tincture of Iodine :

1. It is an antiseptic solution.
2. Iodine is kept in alcohol-water mixture.
3. Concentration of iodine is very low.

How many of the above statements is/are correct ?

None

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All three statements about Tincture of Iodine are correct.
1. It is widely used as an antiseptic solution to disinfect wounds and the skin surface before surgery or injections.
2. Tincture of iodine is traditionally prepared by dissolving iodine (often with potassium iodide or sodium iodide to increase solubility) in a mixture of alcohol (ethanol) and water.
3. The concentration of iodine in tincture of iodine preparations is typically low, ranging from about 2% to 7%. This low concentration is sufficient for its antiseptic effect and minimizes skin irritation.

Tincture of Iodine is an antiseptic solution of iodine in alcohol and water with a low concentration of iodine.

Different concentrations and preparations of iodine solutions exist, including Lugol’s iodine (aqueous solution) and povidone-iodine (an iodophor, where iodine is complexed with a polymer), which are also used as antiseptics or disinfectants. Tincture of iodine is known for its dark brown color.

5. School bells are made of metals because metals are

School bells are made of metals because metals are

Malleable

Sonorous

Ductile

Lustrous

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School bells, and bells in general, are made of metals because metals possess the property of sonority. Sonority is the ability of a material to produce a clear, deep, resonant ringing sound when struck. This property is characteristic of many metals and alloys, especially when shaped appropriately into a bell. Malleability, ductility, and lustrousness are other properties of metals but are not the reason they are used for making bells that produce sound.

Metals are used for making bells because they are sonorous.

Bronze, a metal alloy (primarily copper and tin), is a historically common material for making high-quality bells due to its excellent sonorous properties.

6. Which one of the following pairs of metals are very good conductors of

Which one of the following pairs of metals are very good conductors of heat ?

Silver and Copper

Silver and Lead

Copper and Mercury

Lead and Mercury

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Heat conductivity is the ability of a material to conduct heat. Metals are generally good conductors of heat. Among common metals, silver is the best conductor of heat, followed closely by copper. Both silver and copper are widely used in applications where high thermal conductivity is required. Lead and mercury, while metals, are significantly poorer conductors of heat compared to silver and copper. Therefore, the pair of metals that are very good conductors of heat is Silver and Copper.

Silver and Copper are excellent conductors of heat.

Thermal conductivity values (approximate, W/(m·K) at room temperature): Silver (~429), Copper (~401), Aluminum (~205), Iron (~80), Lead (~35), Mercury (~8.3). This data confirms that Silver and Copper are indeed among the best heat conductors.

7. Milk of Magnesia is used when people suffer from indigestion of food.

Milk of Magnesia is used when people suffer from indigestion of food. It is a

Strong base

Mild base

Strong acid

Mild acid

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Milk of Magnesia is a common name for a suspension of magnesium hydroxide (Mg(OH)₂). Magnesium hydroxide is a base. It is used as an antacid to neutralize excess hydrochloric acid (HCl) in the stomach, which causes indigestion. While it is a base, it is not highly soluble in water, and its reaction with acid is not as vigorous or complete as that of a strong base like sodium hydroxide (NaOH). Therefore, it is considered a mild base, suitable for internal consumption as an antacid or laxative without causing severe side effects associated with strong bases.

Milk of Magnesia is magnesium hydroxide, which acts as a mild base to neutralize stomach acid.

The neutralization reaction in the stomach is: Mg(OH)₂(s) + 2HCl(aq) → MgCl₂(aq) + 2H₂O(l). By consuming a base like magnesium hydroxide, the acidity in the stomach is reduced, providing relief from indigestion and heartburn.

8. Stinging hair of nettle leaves inject fluid in the human body causing

Stinging hair of nettle leaves inject fluid in the human body causing burning pain. The fluid is

Methanoic acid

Tartaric acid

Hydrochloric acid

Sulphuric acid

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The stinging sensation and burning pain caused by contact with nettle leaves (like *Urtica dioica*) are due to fine, brittle hairs (trichomes) on the plant surface that break off and inject chemicals into the skin. The fluid injected contains several irritants, including histamine, acetylcholine, serotonin, and notably, formic acid, which is also known as methanoic acid. Methanoic acid is a simple carboxylic acid that contributes significantly to the burning and stinging sensation.

Nettle stings inject chemicals including methanoic acid (formic acid).

Other acids like tartaric acid are found in fruits like grapes and tamarind. Hydrochloric acid and Sulphuric acid are strong mineral acids not typically found in biological tissues in this manner.

9. Consider the following statements about the Micro, Small and Medium En

Consider the following statements about the Micro, Small and Medium Enterprises (MSMEs) :

1. The MSMEs comprise a dynamic sector of the Indian economy providing large employment opportunities.
2. MSMEs require low capital cost and help industrialization of backward regions.
3. MSMEs contribute enormously to socio-economic development.

How many of the above statements is/are correct ?

None

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All three statements about Micro, Small and Medium Enterprises (MSMEs) are correct.
1. MSMEs are indeed a dynamic sector and are crucial for employment generation in India, providing a large number of jobs.
2. MSMEs generally require lower capital investment compared to large industries and are instrumental in promoting industrialization in backward and rural regions, contributing to balanced regional development.
3. MSMEs make significant contributions to the Indian economy in terms of GDP, exports, employment, and fostering entrepreneurship, thus contributing enormously to socio-economic development.

MSMEs are vital for employment, use lower capital, help regional industrialization, and contribute significantly to the economy.

The MSME sector is a significant contributor to India’s GDP and exports. The government provides various schemes and policies to support and promote the growth of MSMEs. The definition of MSMEs in India is based on investment in plant & machinery or equipment and annual turnover.

10. The Department for Promotion of Industry and Internal Trade (DPIIT) ha

The Department for Promotion of Industry and Internal Trade (DPIIT) has revised the base year index of Eight Core Industries having a combined weight of about 40.27 percent in the Index of Industrial Production. Which one of the following is not one of the Eight Core Industries ?

Coal

Refinery products

Rubber products

Cement

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The Index of Eight Core Industries measures the collective and individual production performance of eight major sectors considered to be the backbone of the Indian economy. These eight industries are Coal, Crude Oil, Natural Gas, Refinery Products, Fertilizers, Steel, Cement, and Electricity. These sectors have a significant weight (about 40.27%) in the overall Index of Industrial Production (IIP). Among the given options, Coal, Refinery products, and Cement are part of the Eight Core Industries. Rubber products are not included in this list.

The Eight Core Industries are Coal, Crude Oil, Natural Gas, Refinery Products, Fertilizers, Steel, Cement, and Electricity.

The Eight Core Industries index is compiled and released by the Office of the Economic Adviser (OEA), Department for Promotion of Industry and Internal Trade (DPIIT), Ministry of Commerce & Industry. The base year for the index was revised from 2004-05 to 2011-12.