Biology

301. Which one of the following microbes causes acidification and curding o

Which one of the following microbes causes acidification and curding of milk ?

[amp_mcq option1=”Lactic Acid Bacillus” option2=”Clostridium botulinum” option3=”Vibrio cholerae” option4=”Saccharomyces cerevisiae” correct=”option1″]

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UPSC NDA-2 – 2017
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Acidification and curding of milk are caused by Lactic Acid Bacillus (or more generally, Lactic Acid Bacteria, LAB). These microbes ferment lactose (milk sugar) into lactic acid, which lowers the pH, causing the milk proteins (casein) to coagulate and curdle.
Lactic Acid Bacteria (LAB), including various species of *Lactobacillus*, *Streptococcus*, and *Lactococcus*, are responsible for the fermentation process that leads to the production of yogurt, cheese, and other fermented milk products.
– *Clostridium botulinum* is a bacterium that produces a potent neurotoxin causing botulism, often associated with improperly canned foods.
– *Vibrio cholerae* is a bacterium that causes cholera, a severe diarrheal disease, typically transmitted through contaminated water.
– *Saccharomyces cerevisiae* is a yeast commonly known as baker’s yeast or brewer’s yeast, used in baking (carbon dioxide production) and alcoholic fermentation.

302. The term ‘Probiotic’ is applied to

The term ‘Probiotic’ is applied to

[amp_mcq option1=”Organic food” option2=”Antacid” option3=”Antibiotic” option4=”Live microbial food supplement” correct=”option4″]

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UPSC NDA-2 – 2017
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The term ‘Probiotic’ is applied to live microbial food supplements. These are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.
Probiotics are beneficial microorganisms, usually bacteria or yeasts, which are consumed to improve the balance of the gut microbiota.
Probiotics are often found in fermented foods like yogurt, kefir, sauerkraut, kimchi, and supplements. They are distinct from prebiotics, which are non-digestible food ingredients that selectively stimulate the growth and activity of beneficial bacteria already in the colon.

303. Which one of the following vitamins has a role in blood clotting ?

Which one of the following vitamins has a role in blood clotting ?

[amp_mcq option1=”Vitamin A” option2=”Vitamin D” option3=”Vitamin E” option4=”Vitamin K” correct=”option4″]

This question was previously asked in
UPSC NDA-2 – 2017
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Vitamin K plays a crucial role in blood clotting. It is essential for the synthesis of several proteins, called coagulation factors, that are necessary for blood to clot properly.
Vitamin K is a fat-soluble vitamin vital for the synthesis of clotting factors (prothrombin, factors VII, IX, and X) in the liver.
– Vitamin A is important for vision, immune function, and cell growth.
– Vitamin D is primarily involved in calcium absorption and bone health.
– Vitamin E is an antioxidant that protects cells from damage.
– A deficiency in Vitamin K can lead to excessive bleeding.

304. Golden rice is a genetically-modified crop plant where the incorporate

Golden rice is a genetically-modified crop plant where the incorporated gene is meant for biosynthesis of

[amp_mcq option1=”Omega-3 fatty acids” option2=”Vitamin A” option3=”Vitamin B” option4=”Vitamin C” correct=”option2″]

This question was previously asked in
UPSC NDA-2 – 2017
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The correct answer is B) Vitamin A.
Golden rice is a genetically modified rice variety designed to synthesize beta-carotene, a precursor of Vitamin A, in the edible part of the grain (endosperm).
The project aimed to address Vitamin A deficiency, a major public health problem in developing countries where rice is a staple food but naturally lacks beta-carotene. The golden color of the rice is due to the accumulation of beta-carotene.

305. Which one of the following statements about microbes is not correct ?

Which one of the following statements about microbes is not correct ?

[amp_mcq option1=”They are used in sewage treatment plants.” option2=”They are used in industrial fermenters for the production of beverages.” option3=”No antibiotic has been obtained from any microbe.” option4=”They are used to get many bioactive molecules for the treatment of diseases.” correct=”option3″]

This question was previously asked in
UPSC NDA-2 – 2017
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The correct answer is C) No antibiotic has been obtained from any microbe.
Statement C is incorrect. Many antibiotics are derived from microbes. For example, Penicillin is obtained from the fungus *Penicillium notatum*, and Streptomycin is obtained from the bacterium *Streptomyces griseus*.
Statements A, B, and D are correct applications of microbes:
A) Microbes (bacteria) are essential in sewage treatment for decomposing organic matter.
B) Microbes like yeast (fungus) are used in fermentation for producing beverages like beer and wine, and bacteria are used for yogurt, cheese, etc.
D) Microbes are genetically engineered or used as sources to produce various bioactive molecules, including insulin, vaccines, enzymes, and certain therapeutic drugs.

306. Intake of which one of the following food components should be minimiz

Intake of which one of the following food components should be minimized by patients having Gouty Arthritis due to elevated serum uric acid level ?

[amp_mcq option1=”Food fibres” option2=”Nucleic acids” option3=”Lipids” option4=”Carbohydrates” correct=”option2″]

This question was previously asked in
UPSC NDA-2 – 2017
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The correct answer is B) Nucleic acids.
Gouty arthritis is caused by elevated levels of uric acid in the blood, which leads to the formation of uric acid crystals in the joints. Uric acid is a metabolic breakdown product of purines. Purines are building blocks of nucleic acids (DNA and RNA).
Foods high in purines (e.g., red meat, organ meats, seafood, certain vegetables like asparagus and spinach, and alcohol) contribute to higher uric acid levels. Therefore, minimizing the intake of foods rich in purines, which are directly linked to the metabolism of nucleic acids, is a key dietary recommendation for patients with gout. While overall diet balance is important, purine restriction is specifically targeted at the root cause of hyperuricemia related to diet.

307. Melanin is the natural pigment that gives colour to human skin, hair a

Melanin is the natural pigment that gives colour to human skin, hair and the iris. It provides protection against

[amp_mcq option1=”Ultraviolet radiation” option2=”Infrared radiation” option3=”X-ray radiation” option4=”Short wave radio radiation” correct=”option1″]

This question was previously asked in
UPSC NDA-2 – 2017
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The correct answer is A) Ultraviolet radiation.
Melanin is a pigment produced by melanocytes in the skin, hair, and eyes. Its primary function is to absorb harmful ultraviolet (UV) radiation from sunlight, thereby protecting the cells from DNA damage and reducing the risk of skin cancer.
The amount and type of melanin produced influence skin, hair, and eye color. More melanin provides greater protection against UV radiation. While skin provides some protection against other forms of radiation, melanin’s specific role as a pigment is most directly linked to absorption of UV radiation.

308. Which one of the following is the scientific name of the causal organi

Which one of the following is the scientific name of the causal organism of elephantiasis ?

[amp_mcq option1=”Ascaris lumbricoides” option2=”Culex pipiens” option3=”Wuchereria bancrofti” option4=”Fasciola hepatica” correct=”option3″]

This question was previously asked in
UPSC NDA-2 – 2017
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The correct answer is C) Wuchereria bancrofti.
Elephantiasis, or Lymphatic Filariasis, is a parasitic disease caused by nematode worms, primarily *Wuchereria bancrofti*, *Brugia malayi*, and *Brugia timori*. These worms block the lymphatic system, leading to swelling.
The infection is transmitted through the bites of infected mosquitoes, mainly Culex, Anopheles, and Aedes species, which serve as vectors. *Ascaris lumbricoides* causes ascariasis. *Fasciola hepatica* is a liver fluke that causes fascioliasis. *Culex pipiens* is a mosquito species, which can be a vector for the disease but is not the causal organism itself.

309. Tendons through which muscles are connected to bones are tightly compa

Tendons through which muscles are connected to bones are tightly compacted bundles of which one of the following long fibrous protein ?

[amp_mcq option1=”Fibrin” option2=”Collagen” option3=”Elastin” option4=”Cellulose” correct=”option2″]

This question was previously asked in
UPSC NDA-2 – 2017
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The correct answer is B) Collagen.
Tendons are tough bands of fibrous connective tissue that connect muscles to bones. They are primarily composed of tightly compacted bundles of collagen fibers.
Collagen is the most abundant protein in the human body and a key structural component of connective tissues, including tendons, ligaments, cartilage, bone, and skin. Elastin is another fibrous protein found in elastic tissues like blood vessels and skin, allowing them to stretch and recoil. Fibrin is a protein involved in blood clotting. Cellulose is a complex carbohydrate that forms the cell walls of plants.

310. Fluoride toothpaste is sometimes recommended because fluoride

Fluoride toothpaste is sometimes recommended because fluoride

[amp_mcq option1=”prevents plaque formation” option2=”hardens the enamel of the tooth” option3=”kills pathogenic bacteria” option4=”prevents tooth ache” correct=”option2″]

This question was previously asked in
UPSC NDA-2 – 2016
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Fluoride toothpaste is sometimes recommended because fluoride hardens the enamel of the tooth.
Fluoride works by strengthening the tooth enamel through a process called remineralization. When fluoride is present in the mouth, it is incorporated into the crystalline structure of the enamel, forming fluorapatite. Fluorapatite is more resistant to acid dissolution than hydroxyapatite, the original mineral in enamel. This increased resistance helps protect teeth from decay caused by acids produced by bacteria in plaque, effectively hardening the enamel and making it more resilient to cavities.
While fluoride can have some antibacterial effects at higher concentrations, its primary mechanism for preventing cavities in toothpaste is by enhancing enamel remineralization and increasing its acid resistance. Brushing action and other ingredients help remove plaque, but fluoride itself doesn’t primarily prevent plaque formation. It helps prevent tooth decay, which is a common cause of toothache, but it is not a direct pain reliever.
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