Food Preservation, Nutrition, Medicine, etc.

11. Why is potassium permanganate used for purifying drinking water ?

Why is potassium permanganate used for purifying drinking water ?

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It kills germs
It dissolves the impurities
It is a reducing agent
It is an oxidizing agent
This question was previously asked in
UPSC NDA-2 – 2017
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The correct answer is It is an oxidizing agent.
Potassium permanganate (KMnO₄) is a strong oxidizing agent. Its oxidizing properties are utilized in water purification to kill bacteria and other microorganisms (germs), and to oxidize impurities like dissolved iron and manganese, causing them to precipitate and be easily removed.
While potassium permanganate does kill germs, this action is a result of its oxidizing property. It does not dissolve impurities; rather, it helps in their precipitation after oxidation. It is distinctly an oxidizing agent, not a reducing agent. Therefore, its role as an oxidizing agent is the fundamental reason for its use in purifying drinking water.

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12. Toothpaste prevents tooth decay by :

Toothpaste prevents tooth decay by :

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neutralizing the excess acidity.
means of emulsification.
the action of fluoride.
making a coat of calcium over the teeth surface.
This question was previously asked in
UPSC NDA-1 – 2023
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The correct answer is C) the action of fluoride.
The primary mechanism by which toothpaste prevents tooth decay is through the action of fluoride. Fluoride incorporated into toothpaste strengthens tooth enamel by promoting the formation of fluorapatite, a crystalline structure more resistant to acid dissolution than hydroxyapatite, the main component of enamel.
Fluoride also aids in the remineralization of early enamel lesions and inhibits the ability of plaque bacteria to produce acids. While toothpaste may also contain ingredients that help neutralize acids (Option A), fluoride is the key active ingredient specifically responsible for the significant reduction in dental caries incidence seen with the widespread use of fluoride toothpaste. Option B (emulsification) is unrelated to preventing decay. Option D (making a coat of calcium) is an inaccurate description of how toothpaste ingredients work.

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13. Among the following, which is not the correct method for keeping the

Among the following, which is not the correct method for keeping the curd ?

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Keeping in stainless steel vessel
Keeping in copper vessel
Keeping in plastic vessel
Keeping in glass vessel
This question was previously asked in
UPSC NDA-1 – 2023
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The correct answer is B) Keeping in copper vessel.
Curd is acidic due to the presence of lactic acid produced during fermentation. Acidic substances can react with certain metals, such as copper, to form potentially harmful salts.
Keeping acidic food like curd in copper vessels is not recommended because the acid can react with the copper metal. This reaction can leach copper ions into the food, potentially leading to health issues if consumed regularly in significant amounts. Stainless steel, plastic, and glass are non-reactive materials commonly used for storing acidic food items safely.

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14. Tooth enamel is made up of which one of the following calcium

Tooth enamel is made up of which one of the following calcium compounds?

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Calcium carbonate
Calcium sulphate
Calcium hydroxide
Calcium phosphate
This question was previously asked in
UPSC NDA-1 – 2019
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Tooth enamel is primarily made up of calcium phosphate in the form of crystalline hydroxyapatite.
– Tooth enamel is the outermost protective layer of the tooth.
– It is the hardest substance in the human body, mainly due to its high mineral content.
– The main mineral component is hydroxyapatite, which is a complex form of calcium phosphate with the chemical formula Ca₅(PO₄)₃(OH).
While calcium phosphate is the general type of compound, the specific crystalline structure is hydroxyapatite. Other forms of calcium phosphate exist, but hydroxyapatite is the key mineral in bones and teeth. Acids produced by bacteria in the mouth can dissolve the hydroxyapatite crystals, leading to tooth decay. Fluoride can help strengthen enamel by incorporating into the crystal structure, forming fluoroapatite, which is less soluble in acid.

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15. A patient’s abdomen (alimentary canal) can be examined by X-ray after

A patient’s abdomen (alimentary canal) can be examined by X-ray after administering which one of the following metal salts in the patient’s meal ?

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Barium sulphate
Barium chloride
Strontium sulphate
Magnesium chloride
This question was previously asked in
UPSC CDS-2 – 2022
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Barium sulphate is administered to patients for X-ray examination of the alimentary canal. This procedure is commonly known as a barium swallow, barium meal, or barium enema depending on the part being examined.
– Barium sulphate (BaSO4) is a contrast agent used in radiology.
– It is opaque to X-rays, allowing the structure of the digestive tract to be visualized.
– It is used because it is insoluble in water and is not absorbed by the body, making it relatively safe for ingestion or rectal administration despite barium being toxic.
Other barium salts, like barium chloride, are soluble and toxic, and thus cannot be used for this purpose. Barium sulphate is chemically inert and passes through the digestive system without being absorbed.

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

Consider the following statements about Tincture of Iodine :

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  • 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 ?

1
2
3
None
This question was previously asked in
UPSC CDS-2 – 2022
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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.

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17. Which one of the following acids is also known as Vitamin C ?

Which one of the following acids is also known as Vitamin C ?

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Methanoic acid
Ascorbic acid
Lactic acid
Tartaric acid
This question was previously asked in
UPSC CDS-2 – 2019
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Vitamin C is a well-known water-soluble vitamin essential for various bodily functions, including the synthesis of collagen, acting as an antioxidant, and supporting the immune system. Its chemical name is Ascorbic acid.
The question asks for the acid also known as Vitamin C. Among the options provided, Ascorbic acid is the correct chemical name for Vitamin C.
Methanoic acid is also known as formic acid. Lactic acid is produced in muscles and found in sour milk. Tartaric acid is a naturally occurring acid found in grapes and other fruits.

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18. Tincture of iodine is an antiseptic for fresh wounds. It is a dilute s

Tincture of iodine is an antiseptic for fresh wounds. It is a dilute solution of elemental iodine, which does not contain

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water
acetone
alcohol
potassium iodide
This question was previously asked in
UPSC CDS-2 – 2017
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The correct answer is acetone.
Tincture of iodine is traditionally a solution of elemental iodine (I₂) and an iodide salt (like potassium iodide, KI) dissolved in alcohol (ethanol) and often with some water. The iodide salt helps to increase the solubility of iodine in the solvent. Acetone is a different solvent (a ketone) and is not a standard component of traditional tincture of iodine. While acetone can be used as a solvent in some antiseptic preparations or for cleaning wounds, it is not typically part of the ‘tincture of iodine’ formulation used as an antiseptic.
The elemental iodine is the primary antiseptic agent in tincture of iodine. The alcohol also has antiseptic properties and helps in the penetration of iodine into tissues. Potassium iodide is added to form triiodide ions (I₃⁻), which are more soluble in water and alcohol than diatomic iodine (I₂), thus increasing the concentration of dissolved iodine available for antiseptic action.

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19. When eggs are heated, the transparent liquid portion around yolk turns

When eggs are heated, the transparent liquid portion around yolk turns solid white. This happens due to the thermal denaturation of

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fats
proteins
ribose sugar
carbohydrates
This question was previously asked in
UPSC CDS-1 – 2024
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B) proteins
– The transparent liquid portion of an egg white primarily consists of proteins, particularly albumen.
– When heat is applied, the proteins undergo a process called denaturation, where their complex structures unfold.
– This unfolding causes the proteins to aggregate and coagulate, transforming the liquid egg white into a solid, opaque mass.
– Fats, ribose sugar, and carbohydrates are also present in eggs, but the solidification upon heating is specifically due to the thermal denaturation of proteins.
– Denaturation is the loss of the three-dimensional structure of a protein or nucleic acid due to stress, such as heat, chemicals, or radiation. In the case of egg white, heat disrupts the bonds holding the protein structure together, leading to irreversible solidification.

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20. Vitamin B₁₂ deficiency causes pernicious anemia. Animals cannot synthe

Vitamin B₁₂ deficiency causes pernicious anemia. Animals cannot synthesize vitamin B₁₂. Humans must obtain all their vitamin B₁₂ from their diet. The complexing metal ion in vitamin B₁₂ is :

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Mg²⁺ (Magnesium ion)
Fe²⁺ (Iron ion)
Co³⁺ (Cobalt ion)
Zn²⁺ (Zinc ion)
This question was previously asked in
UPSC CDS-1 – 2016
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Vitamin B₁₂ is also known as cobalamin. Its name is derived from the fact that its structure contains a central cobalt atom coordinated within a corrin ring system. The complexing metal ion in vitamin B₁₂ is Cobalt, typically in the Co³⁺ oxidation state.
Vitamin B₁₂ is named cobalamin because it contains a cobalt ion.
Magnesium (Mg²⁺) is found in chlorophyll. Iron (Fe²⁺/Fe³⁺) is found in hemoglobin and myoglobin. Zinc (Zn²⁺) is a cofactor in many enzymes.

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