When plated only in nutrient medium, how much time is required for the protoplast to synthesize new cell wall? ?->(Show Answer!)

1. When plated only in nutrient medium, how much time is required for the protoplast to synthesize new cell wall?

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MCQ-> 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 majority 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 posses 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 mm 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?
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MCQ->When plated only in nutrient medium, how much time is required for the protoplast to synthesize new cell wall?....

MCQ-> Cells are the ultimate multi-taskers: they can switch on genes and carry out their orders, talk to each other, divide in two, and much more, all at the same time. But they couldn’t do any of these tricks without a power source to generate movement. The inside of a cell bustles with more traffic than Delhi roads, and, like all vehicles, the cell’s moving parts need engines. Physicists and biologists have looked ‘under the hood’ of the cell and laid out the nuts and bolts of molecular engines.The ability of such engines to convert chemical energy into motion is the envy nanotechnology researchers looking for ways to power molecule-sized devices. Medical researchers also want to understand how these engines work. Because these molecules are essential for cell division, scientists hope to shut down the rampant growth of cancer cells by deactivating certain motors. Improving motor-driven transport in nerve cells may also be helpful for treating diseases such as Alzheimer’s, Parkinson’s or ALS, also known as Lou Gehrig’s disease.We wouldn’t make it far in life without motor proteins. Our muscles wouldn’t contract. We couldn’t grow, because the growth process requires cells to duplicate their machinery and pull the copies apart. And our genes would be silent without the services of messenger RNA, which carries genetic instructions over to the cell’s protein-making factories. The movements that make these cellular activities possible occur along a complex network of threadlike fibers, or polymers, along which bundles of molecules travel like trams. The engines that power the cell’s freight are three families of proteins, called myosin, kinesin and dynein. For fuel, these proteins burn molecules of ATP, which cells make when they break down the carbohydrates and fats from the foods we eat. The energy from burning ATP causes changes in the proteins’ shape that allow them to heave themselves along the polymer track. The results are impressive: In one second, these molecules can travel between 50 and 100 times their own diameter. If a car with a five-foot-wide engine were as efficient, it would travel 170 to 340 kilometres per hour.Ronald Vale, a researcher at the Howard Hughes Medical Institute and the University of California at San Francisco, and Ronald Milligan of the Scripps Research Institute have realized a long-awaited goal by reconstructing the process by which myosin and kinesin move, almost down to the atom. The dynein motor, on the other hand, is still poorly understood. Myosin molecules, best known for their role in muscle contraction, form chains that lie between filaments of another protein called actin. Each myosin molecule has a tiny head that pokes out from the chain like oars from a canoe. Just as rowers propel their boat by stroking their oars through the water, the myosin molecules stick their heads into the actin and hoist themselves forward along the filament. While myosin moves along in short strokes, its cousin kinesin walks steadily along a different type of filament called a microtubule. Instead of using a projecting head as a lever, kinesin walks on two ‘legs’. Based on these differences, researchers used to think that myosin and kinesin were virtually unrelated. But newly discovered similarities in the motors’ ATP-processing machinery now suggest that they share a common ancestor — molecule. At this point, scientists can only speculate as to what type of primitive cell-like structure this ancestor occupied as it learned to burn ATP and use the energy to change shape. “We’ll never really know, because we can’t dig up the remains of ancient proteins, but that was probably a big evolutionary leap,” says Vale.On a slightly larger scale, loner cells like sperm or infectious bacteria are prime movers that resolutely push their way through to other cells. As L. Mahadevan and Paul Matsudaira of the Massachusetts Institute of Technology explain, the engines in this case are springs or ratchets that are clusters of molecules, rather than single proteins like myosin and kinesin. Researchers don’t yet fully understand these engines’ fueling process or the details of how they move, but the result is a force to be reckoned with. For example, one such engine is a spring-like stalk connecting a single-celled organism called a vorticellid to the leaf fragment it calls home. When exposed to calcium, the spring contracts, yanking the vorticellid down at speeds approaching three inches (eight centimetres) per second.Springs like this are coiled bundles of filaments that expand or contract in response to chemical cues. A wave of positively charged calcium ions, for example, neutralizes the negative charges that keep the filaments extended. Some sperm use spring-like engines made of actin filaments to shoot out a barb that penetrates the layers that surround an egg. And certain viruses use a similar apparatus to shoot their DNA into the host’s cell. Ratchets are also useful for moving whole cells, including some other sperm and pathogens. These engines are filaments that simply grow at one end, attracting chemical building blocks from nearby. Because the other end is anchored in place, the growing end pushes against any barrier that gets in its way.Both springs and ratchets are made up of small units that each move just slightly, but collectively produce a powerful movement. Ultimately, Mahadevan and Matsudaira hope to better understand just how these particles create an effect that seems to be so much more than the sum of its parts. Might such an understanding provide inspiration for ways to power artificial nano-sized devices in the future? “The short answer is absolutely,” says Mahadevan. “Biology has had a lot more time to evolve enormous richness in design for different organisms. Hopefully, studying these structures will not only improve our understanding of the biological world, it will also enable us to copy them, take apart their components and recreate them for other purpose.”According to the author, research on the power source of movement in cells can contribute to
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MCQ-> In the annals of investing, Warren Buffett stands alone. Starting from scratch, simply by picking stocks and companies for investment, Buffett amassed one of the epochal fortunes of the twentieth century. Over a period of four decades more than enough to iron out the effects of fortuitous rolls of the dice, Buffett outperformed the stock market, by a stunning margin and without taking undue risks or suffering a single losing year. Buffett did this in markets bullish and bearish and through economies fat and lean, from the Eisenhower years to Bill Clinton, from the l950s to the l990s, from saddle shoes and Vietnam to junk bonds and the information age. Over the broad sweep of postwar America, as the major stock averages advanced by 11 percent or so a year, Buffett racked up a compounded annual gain of 29.2 percent. The uniqueness of this achievement is more significant in that it was the fruit of old-fashioned, long-term investing. Wall Street’s modern financiers got rich by exploiting their control of the public's money: their essential trick was to take in and sell out the public at opportune moments. Buffett shunned this game, as well as the more venal excesses for which Wall Street is deservedly famous. In effect, he rediscovered the art of pure capitalism, a cold-blooded sport, but a fair one. Buffett began his career, working out his study in Omaha in 1956. His grasp of simple verities gave rise to a drama that would recur throughout his life. Long before those pilgrimages to Omaha, long before Buffett had a record, he would stand in a comer at college parties, baby-faced and bright-eyed, holding forth on the universe as a dozen or two of his older, drunken fraternity brothers crowded around. A few years later, when these friends had metamorphosed into young associates starting out on Wall Street, the ritual was the same. Buffett, the youngest of the group, would plop himself in a big, broad club chair and expound on finance while the others sat at his feet. On Wall Street, his homespun manner made him a cult figure. Where finance was so forbiddingly complex, Buffett could explain it like a general-store clerk discussing the weather. He never forgot that underneath each stock and bond, no matter how arcane, there lay a tangible, ordinary business. Beneath the jargon of Wall Street, he seemed to unearth a street from small-town America. In such a complex age, what was stunning about Buffett was his applicability. Most of what Buffett did was imitable by the average person (this is why the multitudes flocked to Omaha). It is curious irony that as more Americans acquired an interest in investing, Wall Street became more complex and more forbidding than ever. Buffett was born in the midst of depression. The depression cast a long shadow on Americans, but the post war prosperity eclipsed it. Unlike the modern portfolio manager, whose mind- set is that of a trader, Buffett risked his capital on the long term growth of a few select businesses. In this, he resembled the magnates of a previous age, such as J P Morgan Sr.As Jack Newfield wrote of Robert Kennedy, Buffett was not a hero, only a hope; not a myth, only a man. Despite his broad wit, he was strangely stunted. When he went to Paris, his only reaction was that he had no interest in sight-seeing and that the food was better in Omaha. His talent sprang from his unrivaled independence of mind and ability to focus on his work and shut out the world, yet those same qualities exacted a toll. Once, when Buffett was visiting the publisher Katharine Graham on Martha’s Vineyard, a friend remarked on the beauty of the sunset. Buffett replied that he hadn't focused on it, as though it were necessary for him to exert a deliberate act of concentration to "focus" on a sunset. Even at his California beachfront vacation home, Buffett would work every day for weeks and not go near the water. Like other prodigies, he paid a price. Having been raised in a home with more than its share of demons, he lived within an emotional fortress. The few people who shared his office had no knowledge of the inner man, even after decades. Even his children could scarcely recall a time when he broke through his surface calm and showed some feeling. Though part of him is a showman or preacher, he is essentially a private person. Peter Lynch, the mutual-fund wizard, visited Buffett in the 1980s and was struck by the tranquility in his inner sanctum. His archives, neatly alphabetized in metal filing cabinets, looked as files had in another era. He had no armies of traders, no rows of electronic screens, as Lynch did. Buffett had no price charts, no computer - only a newspaper clipping from 1929 and an antique ticker under a glass dome. The two of them paced the floor, recounting their storied histories, what they had bought, what they had sold. Where Lynch had kicked out his losers every few weeks, Buffett had owned mostly the same few stocks for years and years. Lynch felt a pang, as though he had traveled back in time. Buffett’s one concession to modernity is a private jet. Otherwise, he derives little pleasure from spending his fabulous wealth. He has no art collection or snazzy car, and he has never lost his taste for hamburgers. He lives in a commonplace house on a tree-lined block, on the same street where he works. His consuming passion - and pleasure - is his work, or, as he calls it, his canvas. It is there that he revealed the secrets of his trade, and left a self-portrait.“Saddle shoes and Vietnam”, as expressed in the passage, refers to: I. Denier cri and Vietnam war II. Growth of leather footwear industry and Vietnam shoe controversy III. Modern U.S. population and traditional expatriates IV. 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