Ribosomes are the centre for : ?->(Show Answer!)

1. Ribosomes are the centre for :

Answer: Protein Synthesis

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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-> Study the following information carefully and answer the questions given below:Eight friends P, Q, R, S, W, X, Y and Z are sitting around a circular table but not necessarily in the same order. Some of them are facing the centre and some others are facing outside (i.e. in a direction opposite to the centre.) Note :(i) Facing the same direction means if one person faces the centre then the other also faces the centre and vice-versa. (ii) Facing the opposite directions means if one person faces the centre then the other faces outside and vice-versa. (iii) Immediate neighbours facing the same direction means if one person faces the centre then the other also faces the centre and vice-versa. (iv) Immediate neighbours facing the opposite directions means if one person faces the centre then the other faces outside and vice-versa. • R sits second to the right of Y. Only two persons sit between R and W. • P sits to the immediate right of W. W faces outside. • Only one person sits between P and Z. Immediate neighbours of P face opposite directions. • Q sits third to the left of Z. Q is not an immediate neighbour of P. • X faces a direction opposite to that of Y. X is an immediate neighbour of neither Y nor P. • Immediate neighbours of S face same direction. P does not face outside. • R and Q face a direction opposite to that of S.Four of the following five are alike in a certain way based on the direction they are facing and so form a group. Which is the one that does not belong to that group?
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MCQ-> Study the following information carefully and answer the questions given below: Eight friends — J, K, L, M, N, 0, P and Q — are sitting around a circular table but not necessarily in the same order. Some of them are facing the centre and some of them are facing outside. (i.e. in a direction opposite to the centre.) Facing the same direction means if one person faces the centre then the other also faces the centre and vice-versa. Facing the opposite direction means if one person faces the centre then the other faces outside and vice-versa. Immediate neighbours facing the same direction means if one neighbour faces the centre then the other also faces the centre and vice-versa. Immediate neighbours facing the opposite direction means if one neighbour faces the centre then the other faces outside and vice-versa. • Only one person sits between K and 0. Q sits third to the right of 0. • M sits to the immediate right of Q. Q faces outside. • L sits second to the left of P. P is not an immediate neighbour of 0. • L faces a direction opposite to that of 0. Immediate neighbours of L face opposite directions. • J sits third to the left of N. J is not an immediate neighbour of P nor K. • M and J face a direction same as that of N.Four of the following five are alike in a certain way based on the directions they are forming and so form a group. Which is the one that does not belong to that group?
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MCQ->Consider the following statements relating to the stability of floating as well as submerged bodies :1. A submerged body is stable when the centre of gravity is below the centre of buoyancy.2. A floating body is stable when the centre of gravity is above the centre of buoyancy.3. A floating body is stable when the centre of gravity is below the metacentre.4. A submerged body is in stable equilibrium when the centre of gravity coincides with the centre of buoyancy.Of these statements :...

MCQ-> Eight persons — E, F, G, H, I, J, K and L — are sitting around a circle at equidistance but not necessarily in the same order. Some of them are facing towards the centre while some others are facing outside the centre. L is sitting third to the left of K. Both K and L are facing towards the outside. H is not an immediate neighbour of K or L. J faces the just opposite direction of H. (It implies that if H is facing towards the centre, J would face outside the centre). J is sitting second to the left of H. Both the immediate neighbours of G face just opposite direction of G. E is an immediate neighbour of K. Both the immediate neighbours of H face just opposite direction of H. E faces towards the centre and he is an immediate neighbour of both K and I. I faces towards the centre.Who amongst the following are not facing towards the centre ?
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