Biology

291. The oxygen evolved during photosynthesis comes from splitting of

The oxygen evolved during photosynthesis comes from splitting of

[amp_mcq option1=”water” option2=”carbon dioxide” option3=”oxygen” option4=”light” correct=”option1″]

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During photosynthesis, the oxygen gas evolved as a byproduct comes from the splitting of water molecules (photolysis).
– The overall equation for photosynthesis is 6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂.
– Experiments using isotopic tracing (specifically, using water labeled with the heavy oxygen isotope ¹⁸O) demonstrated that the ¹⁸O appeared in the evolved oxygen gas, while using carbon dioxide labeled with ¹⁸O resulted in the ¹⁸O appearing in the glucose product, not the oxygen gas.
Water splitting occurs during the light-dependent reactions of photosynthesis, providing electrons for the electron transport chain, protons for the proton gradient used in ATP synthesis, and oxygen as a waste product. The oxygen atoms in glucose are derived from carbon dioxide.

292. The oxygenated blood from the lungs is received by the

The oxygenated blood from the lungs is received by the

[amp_mcq option1=”left auricle” option2=”left ventricle” option3=”right auricle” option4=”right ventricle” correct=”option1″]

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Oxygenated blood from the lungs returns to the heart through the pulmonary veins and is received by the left atrium (also known as the left auricle).
– The circulatory system involves the heart pumping blood to the lungs for oxygenation and then distributing the oxygenated blood to the rest of the body.
– Deoxygenated blood from the body enters the right atrium, goes to the right ventricle, and is pumped to the lungs via the pulmonary artery.
– Oxygenated blood from the lungs enters the left atrium, goes to the left ventricle, and is pumped to the body via the aorta.
The heart has four chambers: the right atrium and right ventricle (handling deoxygenated blood) and the left atrium and left ventricle (handling oxygenated blood). The atria (auricles) are the receiving chambers, and the ventricles are the pumping chambers.

293. The acidic semidigested food coming out of the stomach is neutralized

The acidic semidigested food coming out of the stomach is neutralized by

[amp_mcq option1=”pancreatic juice” option2=”duodenal secretion” option3=”large intestine secretion” option4=”bile juice” correct=”option1″]

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The acidic semidigested food (chyme) coming out of the stomach into the duodenum is neutralized primarily by the bicarbonate ions present in pancreatic juice. Bile juice and duodenal secretions also contribute bicarbonate.
– Stomach contents are highly acidic (pH 1.5-3.5) due to hydrochloric acid.
– Enzymes in the small intestine, particularly pancreatic enzymes, function optimally in a slightly alkaline environment (pH 7-8).
– Pancreatic juice is rich in bicarbonate ions (HCO₃⁻), which effectively neutralize the acidity of the chyme entering the duodenum, raising the pH to the optimal range for enzyme activity.
Bile juice, produced by the liver, is also alkaline (pH 7.6-8.6) due to bicarbonate ions absorbed from the blood and secreted by bile duct cells, and it also helps in neutralization, in addition to its primary role in fat emulsification. Duodenal glands (Brunner’s glands) also secrete alkaline mucus containing bicarbonate, providing protection and lubrication. However, pancreatic juice is generally considered the main source of bicarbonate for bulk neutralization in the duodenum.

294. Which one of the following is a waterborne disease?

Which one of the following is a waterborne disease?

[amp_mcq option1=”Jaundice” option2=”Tuberculosis” option3=”Rabies” option4=”Arthritis” correct=”option1″]

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Jaundice, when caused by Hepatitis A or Hepatitis E, is a symptom related to waterborne transmission.
– Waterborne diseases are caused by pathogens transmitted through contaminated water.
– Hepatitis A and Hepatitis E viruses, which cause liver inflammation leading to jaundice (yellowing of skin/eyes), are typically spread through the faecal-oral route, often via contaminated water or food.
– Tuberculosis is airborne.
– Rabies is spread through animal bites.
– Arthritis is joint inflammation with various causes, not typically infectious or waterborne.
While jaundice is a symptom and not a disease itself, among the given options, it is the only condition directly linked to waterborne pathogens (specifically, the viruses causing Hepatitis A and E). Therefore, in the context of potential UPSC-style options, Jaundice (as a manifestation of waterborne Hepatitis) is the intended answer.

295. Which of the following kingdoms has/have only unicellular organisms?

Which of the following kingdoms has/have only unicellular organisms?

[amp_mcq option1=”Monera only” option2=”Protista only” option3=”Monera and Protista both” option4=”Protista and Fungi both” correct=”option1″]

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The kingdom Monera consists only of unicellular organisms.
– In the five-kingdom classification system, Monera includes all prokaryotic organisms, such as bacteria and cyanobacteria, which are exclusively unicellular.
– Protista primarily consists of unicellular eukaryotic organisms, but some simple multicellular or colonial forms are also classified under Protista depending on the system.
– Fungi includes both unicellular (like yeast) and multicellular organisms.
– Plantae and Animalia consist entirely of multicellular organisms.
The question asks which kingdom *only* has unicellular organisms. While Protista is predominantly unicellular, Monera is strictly unicellular. Thus, Monera is the most accurate answer meeting the condition of having *only* unicellular organisms.

296. Damage to the apical meristem of a growing young plant will affect the

Damage to the apical meristem of a growing young plant will affect the

[amp_mcq option1=”length of the plant” option2=”colour of the flower” option3=”colour of the leaves” option4=”taste of the fruits” correct=”option1″]

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Damage to the apical meristem of a growing young plant will primarily affect its length.
– Apical meristems are located at the tips of shoots and roots.
– They are responsible for primary growth, which results in an increase in the length of the plant.
– Damage to these meristems inhibits or stops this primary growth.
Other types of meristems include lateral meristems (like cambium), responsible for secondary growth (increase in girth or diameter), and intercalary meristems (found at the base of leaves or internodes), responsible for increasing the length of internodes. The colour of flowers or leaves is related to pigments, and the taste of fruits is related to metabolic products, none of which are directly and immediately affected by damage to the apical meristem as significantly as the plant’s length.

297. One of the additional functions of Smooth Endoplasmic Reticulum (SER)

One of the additional functions of Smooth Endoplasmic Reticulum (SER) is

[amp_mcq option1=”protein synthesis” option2=”lipid synthesis” option3=”storage of biomolecules” option4=”detoxification of toxic substances” correct=”option4″]

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The Smooth Endoplasmic Reticulum (SER) performs several key functions distinct from the Rough Endoplasmic Reticulum (RER), which is primarily involved in protein synthesis. These functions of SER include lipid synthesis (phospholipids, steroids), detoxification of drugs and poisons (especially in liver cells), metabolism of carbohydrates, and storage of calcium ions (critical for muscle contraction). Among the given options, detoxification of toxic substances is a well-established function of SER.
– RER has ribosomes on its surface and is involved in synthesizing and modifying proteins destined for secretion or insertion into membranes.
– SER lacks ribosomes and is involved in metabolic processes.
– Key functions of SER include lipid synthesis, detoxification, carbohydrate metabolism, and calcium storage.
For example, in hepatocytes (liver cells), the SER contains enzymes that catalyze reactions to detoxify lipid-soluble drugs and harmful metabolic products by making them more water-soluble for excretion from the body. SER is also extensive in cells that synthesize steroids (like hormone-producing cells).

298. Which one of the following groups of cellular organelles contains DNA?

Which one of the following groups of cellular organelles contains DNA?

[amp_mcq option1=”Mitochondria, nucleus, chloroplast” option2=”Mitochondria, Golgi bodies, nucleus” option3=”Mitochondria, plasma membrane, nucleus” option4=”Chloroplast, nucleus, ribosomes” correct=”option1″]

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In eukaryotic cells, DNA is primarily located in the nucleus. Additionally, mitochondria (in both plant and animal cells) and chloroplasts (in plant cells and algae) possess their own circular DNA (mtDNA and cpDNA, respectively), which contains genes essential for their function and reproduction.
– Nucleus: Contains the majority of the cell’s genetic material in the form of linear chromosomes.
– Mitochondria: Contain a small, circular genome (mtDNA) involved in cellular respiration.
– Chloroplasts: Contain a small, circular genome (cpDNA) involved in photosynthesis.
The endosymbiotic theory suggests that mitochondria and chloroplasts originated from free-living bacteria that were engulfed by early eukaryotic cells, retaining their own genetic material and ribosomes. Golgi bodies, plasma membrane (cellular membrane), and ribosomes do not contain DNA.

299. Bats detect obstacles in their path by receiving the reflected

Bats detect obstacles in their path by receiving the reflected

[amp_mcq option1=”Infrasonic waves” option2=”Ultrasonic waves” option3=”Radio waves” option4=”Microwaves” correct=”option2″]

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The correct answer is Ultrasonic waves.
Bats use a process called echolocation to navigate and find prey in the dark. They emit high-frequency sound waves, which are beyond the range of human hearing (ultrasonic waves). These waves reflect off objects in their path, and the bat detects the returning echoes, interpreting them to build a ‘sound map’ of their surroundings, thus detecting obstacles and prey.
Infrasonic waves are sound waves with frequencies below the human hearing range. Radio waves and microwaves are types of electromagnetic radiation, not sound waves, and are not used by bats for echolocation.

300. Who among the following shared the Nobel Prize in 1962 along with Fran

Who among the following shared the Nobel Prize in 1962 along with Francis Crick and James Watson for their discoveries concerning the molecular structure of nucleic acids ?

[amp_mcq option1=”Erwin Chargaff” option2=”Maurice Hugh Frederick Wilkins” option3=”Rosalind Franklin” option4=”Phoebus Levene” correct=”option2″]

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The Nobel Prize in Physiology or Medicine in 1962 was awarded jointly to James Watson, Francis Crick, and Maurice Hugh Frederick Wilkins for their discoveries concerning the molecular structure of nucleic acids (specifically DNA).
The discovery of the double helix structure of DNA by Watson, Crick, and Wilkins, significantly aided by the X-ray diffraction work of Rosalind Franklin (who was not awarded as the prize is not posthumous), was a landmark achievement in molecular biology.
– Erwin Chargaff is known for Chargaff’s rules, which state that in DNA, the amount of adenine (A) is approximately equal to the amount of thymine (T), and the amount of guanine (G) is approximately equal to the amount of cytosine (C). His work was important for Watson and Crick but he did not share the Nobel Prize for this discovery.
– Rosalind Franklin’s X-ray diffraction images (particularly Photo 51) were critical evidence used by Watson and Crick to determine the structure of DNA.
– Phoebus Levene is known for his work on the structure of nucleotides and nucleic acids in the early 20th century, including identifying the components of DNA (phosphate, sugar, base).
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