Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Nutritional calcium is a vital mineral required for the growth and maintenance of strong bones and teeth. It also plays a crucial role in muscle function, nerve signaling, and blood clotting. Rice is not a significant source of calcium. While it provides carbohydrates and small nutrients it does not contain notable calcium levels. Fortified rice may contain added calcium but regular rice lacks this essential mineral for bone health. Options (b), (c), and (d) are incorrect:

Ragi or finger millet is an excellent plant-based source of calcium. It provides a good amount of calcium which is important for strong bones and teeth. Ragi is highly valued in regions where it is cultivated as a nutritious calcium-rich food. Skimmed milk is a good source of calcium and helps maintain bone health. Despite having reduced fat content skimmed milk retains high calcium levels. Dairy products like skimmed milk are among the best natural calcium sources. Eggs contain small amounts of calcium mainly found in the yolk. However they are not considered a major source of calcium compared to dairy products or fortified foods.

Explanation

Statement 1 is correct: Caffeine, a constituent of tea and coffee is a diuretic. It means it increases urine production by promoting fluid loss from the body. It acts by inhibiting the reabsorption of sodium and water in the kidneys which leads to increased urination.

Statement 2 is correct: Citric acid is a common additive in soft drinks. It is used to add tartness and flavor, and it also helps to preserve the drinks. Citric acid occurs naturally in citrus fruits such as lemons and oranges, and its acidic nature helps balance the sweetness of soft drinks and prolong shelf life.

Statement 3 is correct: Ascorbic acid, commonly known as Vitamin C, plays a crucial role in the synthesis of collagen, a protein that is essential for the structure of bones, teeth, skin, blood vessels, and cartilage. Deficiency in Vitamin C can lead to scurvy, a condition characterized by weakened connective tissue, bleeding gums, and joint pain due to impaired collagen formation.

Statement 4 is incorrect: Citric acid primarily serves as a flavoring agent and preservative. While it has antioxidant properties, it does not provide the essential health benefits of Vitamin C. Ascorbic acid (Vitamin C) is crucial for collagen formation, immune function, and iron absorption, making it irreplaceable by citric acid in these vital bodily processes.

Explanation

ELISA (Enzyme-Linked Immunosorbent Assay) is an immunological assay technique used to detect and quantify the presence of antibodies or antigens in a sample.

Statement 1 is incorrect: ELISA is not typically the first or most basic test for diagnosing cancer. Other tests, including imaging studies (X-rays, CT scans, MRIs), biopsies, and blood tests specific to cancer (e.g., PSA for prostate cancer, CA-125 for ovarian cancer) are usually used first. ELISA is used in a variety of diagnostic settings, such as for detecting infections (e.g., HIV, Hepatitis B) or monitoring immune responses.

Statement 2 is incorrect: Around 85% of humans have Rh+ (Rhesus positive) blood, meaning their red blood cells carry the Rh factor protein. Only 15% of humans have Rh- blood, lacking this protein. The presence or absence of the Rh factor is critical in blood transfusions and pregnancy.

Explanation

Option (d) is correct: The hepatic portal vein is the blood vessel that carries nutrient-rich blood from the stomach and small intestine to the liver. This blood is rich in nutrients absorbed from digested food and it contains waste products that need to be processed by the liver. In the liver, these nutrients are processed, stored, or released into the bloodstream as needed. The liver also detoxifies harmful substances present in the blood before returning it to the general circulation. Options (a), (b), and (c) are incorrect:

Left Hepatic Artery supplies oxygenated blood to the liver but is not responsible for carrying nutrient-rich blood from the digestive system. Hepatic Vein carries deoxygenated blood from the liver to the inferior vena cava, which returns it to the heart. It does not carry blood from the stomach or intestine to the liver. Right Hepatic Artery also supplies oxygenated blood to the liver but does not carry nutrient-rich blood from the digestive system.

Explanation

Pair (b) is incorrectly matched: The first human embryo cloning was achieved in the United States. In 2001, scientists at Advanced Cell Technology in Massachusetts (USA) successfully cloned a human embryo. The cloned embryo only developed to the 6-cell stage before it stopped dividing and was destroyed. This was far from a fully developed embryo, and the experiment was not considered a complete success. The first verified and successful cloning of a human embryo to produce stem cells was achieved in 2013 by scientists at the Oregon Health & Science University, led by Shoukhrat Mitalipov. They used somatic cell nuclear transfer (SCNT) to create a cloned embryo that developed to the blastocyst stage, from which stem cells were derived. Germany has strict regulations against human cloning and it is not the country where the first human embryo cloning took place. Pairs (a), (c), and (d) are correctly matched:

In 1997, scientists in the U.K. created the world’s first genetically modified mouse with a full human chromosome, specifically the human chromosome 21. In 2005, NASA’s Deep Impact mission successfully guided a spacecraft to collide with comet Tempel 1. This was the first mission in history to deliberately crash a spacecraft into a comet to study its composition. Japan’s JAXA (Japan Aerospace Exploration Agency) successfully landed the Hayabusa spacecraft on the asteroid Itokawa in 2005. The mission was designed to collect samples from the asteroid and return them to Earth.

Explanation

Meningococcal meningitis is a severe bacterial infection caused by Neisseria meningitidis. It inflames the protective membranes (meninges) surrounding the brain and spinal cord. It spreads through respiratory droplets and can lead to life-threatening complications like sepsis, brain damage, or death if untreated.

Statement 1 is incorrect: Meningococcal meningitis is not transmitted by mosquito bites. It spreads through respiratory droplets when an infected person coughs, sneezes, or talks. It can also spread through close contact, such as kissing or sharing items like utensils or drinks.

Statement 2 is correct: Vomiting and neck pain are common symptoms of meningococcal meningitis. Individuals may also experience fever, headache, sensitivity to light, confusion, and seizures.

Explanation

Dr. V. Mohan Reddy is renowned for performing a successful open-heart procedure called the arterial switch operation on an infant. This operation is a complex cardiac surgery used to correct transposition of the great arteries, a congenital heart defect where the major arteries are reversed. This breakthrough surgery provided new hope for treating congenital heart diseases in infants and gained recognition as a landmark achievement in pediatric cardiac surgery.

Explanation

NASA’s THEMIS mission (launched in 2007) investigates the origin and mechanisms of auroras, the colorful lights in high-latitude skies caused by interactions between Earth’s magnetosphere and solar wind. The mission studies substorms--sudden energy releases in the magnetosphere--and processes like magnetic reconnection and plasma waves. that magnetotail reconnection triggers substorms, improving understanding of space weather and its impacts on satellites, communication systems. The mission contributes to heliophysics by exploring Earth’s magnetosphere dynamics. Its primary goal was to study auroras and their connection to energy releases in the magnetosphere.

Explanation

Statement 1 is incorrect: A geostationary satellite orbits the Earth at an altitude of approximately 35,786 km(not 10,000 km) above the equator. This altitude ensures that the satellite’s orbital period matches the Earth’s rotational period, making it appear stationary from the ground.

Statement 2 is correct: FM (Frequency Modulation) is less affected by noise because noise primarily affects amplitude, not frequency. This makes FM transmission superior in quality compared to AM (Amplitude Modulation).

Explanation

LNG is natural gas that has been cooled to a liquid form, making it easier to transport across long distances where pipelines are not feasible. Liquefied Natural Gas (LNG) and Natural Gas Liquids (NGL) play crucial roles in the global energy market, facilitating the storage, transportation, and consumption of natural gas.

Statement 1 is correct: LNG is natural gas cooled to approximately -162°C at normal atmospheric pressure, making it a liquid for ease of storage and transportation in specialized cryogenic tanks.

Statement 2 is incorrect: The first LNG terminal in India was built at Dahej, Gujarat, not Hassan.

Statement 3 is correct: Natural Gas Liquids (NGLs), such as ethane, propane, butane, and natural gasoline, are extracted from natural gas and can be separated from LPG.