The membrane-bound nucleus is the most prominent feature of the eukaryotic cell.
Schleiden and Schwann, when setting forth the cell doctrine in the 1830s, considered that it had a central role in growth and development. Their belief has been fully supported even though they had only vague notions as to what that role might be, and how the role was to be expressed in some cellular action. The membraneless nuclear area of the prokaryotic cell, with its tangle of fine threads, is now known to play a similar role.
Some cells, like the sieve tubes of vascular plants and the red blood cells of mammals, do not possess nuclei during the greater part of their existence, although they had nuclei when in a less differentiated state. Such cells can no longer divide and their life span is limited. Other cells are regularly multinucleate. Some, like the cells of striated muscles or the latex vessels of higher plants, become so through cell fusion. Some, like the unicellular protozoan paramecium, are normally binucleate, one of the nuclei serving as a source of hereditary information for the next generation, the other governing the day-to-day metabolic activities of the cell. Still other organisms, such as some fungi, are multinucleate because cross walls, dividing the mycelium into specific cells, are absent or irregularly present. The uninucleate situation, however, is typical for the vast minority of cells, and it would appear that this is the most efficient and most economical manner of partitioning living substance into manageable units. This point of view is given credence not only by the prevalence of uninucleate cells, but because for each kind of cell there is a ratio maintained between the volume of the nucleus and that of the cytoplasm. If we think of the nucleus as the control centre of the cell, this would suggest that for a given kind of cell performing a given kind of work, one nucleus can ‘take care of’ a specific volume of cytoplasm and keep it in functioning order. In terms of material and energy, this must mean providing the kind of information needed to keep flow of materials and energy moving at the correct rate and in the proper channels. With the multitude of enzymes in the cell, materials and energy can of course be channelled in a multitude of ways; it is the function of some information molecules to make channels of use more preferred than others at any given time. How this regulatory control is exercised is not entirely clear.
The nucleus is generally a rounded body. In plant cells, however, where the centre of the cell is often occupied by a large vacuole, the nucleus may be pushed against the cell wall, causing it to assume a lens shape. In some white blood cells, such as polymorphonucleated leukocytes, and in cells of the spinning gland of some insects and spiders, the nucleus is very much lobed. The reason for this is not clear, but it may relate to the fact that for a given volume of nucleus, a lobate form provides a much greater surface area for nuclear-cytoplasmic exchanges, possibly affecting both the rate and the amount of metabolic reactions. The nucleus, whatever its shape, is segregated from the cytoplasm by a double membrane, the nuclear envelope, with the two membranes separated from each other by a perinuclear space of varying width. The envelope is absent only during the time of cell division, and then just for a brief period. The outer membrane is often continuous with the membranes of the endoplasmic reticulum, a possible retention of an earlier relationship, since the envelope, at least in part, is formed at the end cell division by coalescing fragments of the endoplasmic reticulum. The cytoplasmic side of the nucleus is frequently coated with ribosomes, another fact that stresses the similarity and relation of the nuclear envelope to the endoplasmic reticulum. The inner membrane seems to possess a crystalline layer where it abuts the nucleoplasm, but its function remains to be determined.
Everything that passes between the cytoplasm and the nucleus in the eukaryotic cell must transverse the nuclear envelope. This includes some fairly large molecules as well as bodies such as ribosomes, which measure about 25 nm in diameter. Some passageway is, therefore, obviously necessary since there is no indication of dissolution of the nuclear envelope in order to make such movement possible. The nuclear pores appear to be reasonable candidates for such passageways. In plant cells these are irregularly, rather sparsely distributed over the surface of the nucleus, but in the amphibian oocyte, for example, the pores are numerous, regularly arranged, and octagonal and are formed by the fusion of the outer and inner membrane
Which of the following kinds of cells never have a nuclei?
Show Hint
- Sieve Tubes
- Red blood cells of mammals
- Prokaryotic cells
- None of these
The Correct Option is C
Solution and Explanation
Sieve tubes and RBCs lose their nuclei during maturity, but once had them.
Thus, (c) is correct.
According to the first paragraph, the contention of Schleiden and Schwann that the nucleus is the most important part of the cell has
Show Hint
- been proved to be true.
- has been true so far but false in the case of the prokaryotic cell.
- is only partially true.
- has been proved to be completely false.
The Correct Option is A
Solution and Explanation
Thus, (a) is correct.
It may be inferred from the passage that the vast majority of cells are
Show Hint
- multinucleate.
- binucleate.
- uninucleate.
- anunucleate.
The Correct Option is C
Solution and Explanation
Hence, (c) is correct.
What is definitely a function of the nuclei of the normally binucleate cell?
Show Hint
- To arrange for the growth and nourishment of the cell.
- To hold hereditary information for the next generation.
- To make up the basic physical structure of the organism.
- To fight the various foreign diseases attacking the body.
The Correct Option is B
Solution and Explanation
Thus, (b) is correct.
The function of the crystalline layer of the inner membrane of the nucleus is
Show Hint
- generation of nourishment of the cell.
- holding together the disparate structures of the endoplasmic reticulum.
- helping in transversal of the nuclear envelope.
- Cannot be determined from the passage.
The Correct Option is D
Solution and Explanation
Thus, (d) is correct.
Why, according to the passage, is the polymorphonucleated leukocyte probably lobed?
Show Hint
- Because it is quite convoluted in its functions.
- Because it is the red blood cell which is the most important cell in the body.
- Because it provides a greater area for metabolism reactions.
- Because it provides greater strength to the spider web due to greater area.
The Correct Option is C
Solution and Explanation
Thus, (c) is correct.
Why, according to the passage, are fungi multinucleate?
Show Hint
- Because they need more food to survive.
- Because they frequently lack walls dividing the mycelium.
- Because the mycelium is area wise much bigger than other cells.
- Cannot be determined from the passage.
The Correct Option is B
Solution and Explanation
Thus, (b) is correct.
Top Questions on Reading Comprehension
- ”In recent years, technological advancements in AI and machine learning have fundamentally altered how we approach daily tasks. The growing reliance on these systems brings both challenges and opportunities, especially in areas like automation, healthcare, and customer service.”
What is the primary concern regarding the increased use of AI in daily tasks as mentioned in the passage?
- NMAT - 2025
- English Language Comprehension
- Reading Comprehension
Meta is recalibrating content on its social media platforms as the political tide has turned in Washington, with Mark Zuckerberg announcing last week that his company plans to fire its US fact-checkers. Fact-checking evolved in response to allegations of misinformation and is being watered down in response to accusations of censorship. Social media does not have solutions to either. Community review — introduced by Elon Musk at X and planned by Zuckerberg for Facebook and Instagram — is not a significant improvement over fact-checking. Having Washington lean on foreign governments over content moderation does not benefit free speech. Yet, that is the nature of the social media beast, designed to amplify bias.
Information and misinformation continue to jostle on social media at the mercy of user discretion. Social media now has enough control over all other forms of media to broaden its reach. It is the connective tissue for mass consumption of entertainment, and alternative platforms are reworking their engagement with social media. Technologies are shaping up to drive this advantage further through synthetic content targeted precisely at its intended audience. Meta’s algorithm will now play up politics because it is the flavour of the season.
The Achilles’ Heel of social media is informed choice which could turn against misinformation. Its move away from content moderation is driven by the need to be more inclusive, yet unfiltered content can push users away from social media towards legacy forms that have better moderation systems in place. Lawmakers across the world are unlikely to give social media a free run, even if Donald Trump is working on their case. Protections have already been put in place across jurisdictions over misinformation. These may be difficult to dismantle, even if the Republicans pull US-owned social media companies further to the right.
Media consumption is, in essence, evidence-based judgement that mediums must adapt to. Content moderation, not free speech, is the adaptation mechanism. Musk and Zuckerberg are not exempt- IPMAT - 2025
- Verbal and Logical Ability
- Reading Comprehension
According to the French philosopher Jean Baudrillard, commodities available for consumption are not inherently negative things. Baudrillard tried to interpret consumption in modern societies by engaging with the ’cargo myth’ prevalent among the indigenous Melanesian people living in the South Pacific. The Melanesians did not know what aeroplanes were. However,they saw that these winged entities descended from the air for white people and appeared to make them happy. They also noted that aeroplanes never descended for the Melanesian people. The Melanesian natives noted that the white people had placed objects similar to the aeroplane on the ground. They concluded that these objects were attracting the aeroplanes in the air and bringing them to the ground. Through a magical process, the aeroplanes were bringing plenty to the white people and making them happy. The Melanesian people concluded that they would need to place objects that simulated the aeroplane on the ground and attract them from the air. Baudrillard believes that the cargo myth holds an important analogy for the ways in which consumers engage with objects of consumption.
According to Baudrillard, the modern consumer ”sets in place a whole array of sham objects, of characteristic signs of happiness, and then waits for happiness to alight”. For instance, modern consumers believe that they will get happiness if they buy the latest available version of a mobile phone or automobile. However, consumption does not usually lead to happiness. While consumers should ideally be blaming their heightened expectations for their lack of happiness, they blame the commodity instead.
They feel that they should have waited for the next version of a mobile phone or automobile before buying the one they did. The version they bought is somehow inferior and therefore cannot make them happy. Baudrillard argues that consumers have replaced ’real’ happiness with ’signs’ of happiness. This results in the endless deferment of the arrival of total happiness. In Baudrillard’s words, ”in everyday practice, the blessings of consumption are not experienced as resulting from work or from a production process; they are experienced as a miracle”. Modern consumers view consumption in the same magical way as the Melanesian people viewed the aeroplanes in the cargo myth. Television commercials also present objects of consumption as miracles. As a result, commodities appear to be distanced from the social processes which lead to their production. In effect, objects of consumption are divorced from the reality which produces them.- IPMAT - 2025
- Verbal and Logical Ability
- Reading Comprehension
CONVERSATION ANALYSIS: Read the following transcript and choose the answer that is closest to each of the questions that are based on the transcript.
Lucia Rahilly (Global Editorial Director, The McKinsey Podcast): Today we’re talking about the next big arenas of competition, about the industries that will matter most in the global business landscape, which you describe as arenas of competition. What do we mean when we use this term?
Chris Bradley (Director, McKinsey Global Institute): If I go back and look at the top ten companies in 2005, they were in traditional industries such as oil and gas, retail, industrials, and pharmaceuticals. The average company was worth about $250 billion. If I advance the clock forward to 2020, nine in ten of those companies have been replaced, and by companies that are eight times bigger than the old guards.
And this new batch of companies comes from these new arenas or competitive sectors. In fact, they’re so different that we have a nickname for them. If you’re a fan of Harry Potter, it’s wizards versus muggles.
Arena industries are wizardish; we found that there’s a set of industries that play by very different set of economic rules and get very different results, while the rest, the muggles (even though they run the world, finance the world, and energize the world), play by a more traditional set of economic rules.
Lucia Rahilly: Could we put a finer point on what is novel or different about the lens that you applied to determine what’s a wizard and what’s a muggle?
Chris Bradley: Wizards are defined by growth and dynamism. We looked at where value is flowing and the places where value is moving. And where is the value flowing? What we see is that this set of wizards, which represent about ten percent of industries, hog 45 percent of the growth in market cap. But there’s another dimension or axis too, which is dynamism. That is measured by a new metric we’ve come up with called the ”shuffle rate.” How much does the bottom move to the top? It turns out that in this set of wizardish industries, or arenas, the shuffle rate is much higher than it is in the traditional industry.
Lucia Rahilly: So, where are we seeing the most profit?
Chris Bradley: The economic profit, which is the profit you make minus the cost for the capital you employ is in the wizard industries. It’s where R&D happens; they’re two times more R&D intensive. They’re big stars, the nebulae, where new business is born.- IPMAT - 2025
- Verbal and Logical Ability
- Reading Comprehension
- On the first day of January 2025, the Indian Meteorological Department [IMD] announced that 2024 was the hottest year on record. A study by the Council on Energy, Environment and Water shows that nearly eight out of ten Indians live in districts that are at risk of either a flood, a cyclone, or a drought. Nearly twenty three States in India are heatwave-prone. In the summer of 2024, India recorded more than 44,000 cases of heatstroke and over 300 heat-related mortalities, as per the bulletin of the Ministry of Health and Family Welfare. Water reservoirs and the energy demand that keeps India powered are impacted too. During a ten-day long heatwave in Delhi, peak power demand was 16% higher than the previous year.
- IPMAT - 2025
- Verbal and Logical Ability
- Reading Comprehension
Questions Asked in CAT exam
- There is a sentence that is missing in the paragraph below. Look at the paragraph and decide where (option 1, 2, 3, or 4) the following sentence would best fit.
Sentence: Understanding central Asia’s role helps developments make more sense not only across Asia but in Europe, the Americas and Africa.
Paragraph: The nations of the Silk Roads are sometimes called ‘developing countries’, but they are actually some of the world’s most highly developed countries, the very crossroads of civilization, in advanced states of disrepair. ___(1)___. These countries lie at the centre of global affairs: they have since the beginning of history. Running across the spine of Asia, they form a web of connections fanning out in every direction, routes along which pilgrims and warriors, nomads and merchants have travelled, goods and produce have been bought and sold, and ideas exchanged, adapted and refined. ___(2)___ .They have carried not only prosperity, but also death and violence, disease and disaster. ___(3)___. The Silk Roads are the world’s central nervous system, connecting otherwise far-flung peoples and places…. ___(4)___. It allows us to see patterns and links, causes and effects that remain invisible if one looks only at Europe, or North America.- CAT - 2024
- Para Completion
- Let $x$, $y$, and $z$ be real numbers satisfying
\(4(x^2 + y^2 + z^2) = a,\)
\(4(x - y - z) = 3 + a.\)
Then $a$ equals ?- CAT - 2024
- Algebra
- The passage given below is followed by four alternate summaries. Choose the option that best captures the essence of the passage.
Certain codes may, of course, be so widely distributed in a specific language community or culture, and be learned at so early an age, that they appear not to be constructed – the effect of an articulation between sign and referent – but to be ‘naturally’ given. Simple visual signs appear to have achieved a ‘near-universality’ in this sense: though evidence remains that even apparently ‘natural’ visual codes are culture specific. However, this does not mean that no codes have intervened; rather, that the codes have been profoundly naturalized. The operation of naturalized codes reveals not the transparency and ‘naturalness’ of language but the depth, the habituation and the near-universality of the codes in use. They produce apparently ‘natural’ recognitions. This has the (ideological) effect of concealing the practices of coding which are present.- CAT - 2024
- Para Summary
- There is a sentence that is missing in the paragraph below. Look at the paragraph and decide where (option 1, 2, 3, or 4) the following sentence would best fit.
Sentence: Comprehending a wide range of emotions, Renaissance music nevertheless portrayed all emotions in a balanced and moderate fashion.
Paragraph: A volume of translated Italian madrigals were published in London during the year of 1588. This sudden public interest facilitated a surge of English Madrigal writing as well as a spurt of other secular music writing and publication. ___(1)___. This music boom lasted for thirty years and was as much a golden age of music as British literature was with Shakespeare and Queen Elizabeth I. ___(2)___. The rebirth in both literature and music originated in Italy and migrated to England; the English madrigal became more humorous and lighter in England as compared to Italy. Renaissance music was mostly polyphonic in texture. ___(3)___. Extreme use of and contrasts in dynamics, rhythm, and tone colour do not occur. ___(4)___. The rhythms in Renaissance music tend to have a smooth, soft flow instead of a sharp, well-defined pulse of accents.- CAT - 2024
- Para Completion
- There is a sentence that is missing in the paragraph below. Look at the paragraph and decide where (option 1, 2, 3, or 4) the following sentence would best fit.
Sentence: [T]he Europeans did not invent globalization.
Paragraph: The first phase of globalization occurred long before the introduction of either steam or electric power…Chinese consumers at all social levels consumed vast quantities of spices, fragrant woods and unusual plants. The peoples of Southeast Asia who lived in forests gave up their traditional livelihoods and completely reoriented their economies to supply Chinese consumers….___(1)___. These exchanges of the year 1000 opened some of the routes through which goods and peoples continued to travel after Columbus traversed the mid-Atlantic. ___(2)___. Yet the world of 1000 differed from that of 1492 in important ways….the travellers who encountered one another in the year 1000 were much closer technologically. ___(3)___. They changed and augmented what was already there since 1000. ___(4)___. If globalization hadn’t yet begun, Europeans wouldn’t have been able to penetrate the markets in so many places as quickly as they did after 1492.- CAT - 2024
- Para Completion