protein)ie activated, cells will divide. A dom too ightly to GDP, You introduce
ID: 258122 • Letter: P
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protein)ie activated, cells will divide. A dom too ightly to GDP, You introduce the mutant form o 26. When Ras (Small O normal cells in cells. Which of A The cells ular signals that typically activate Ras. activate Ras will divide more frequently compared to extracellular signals that typically activate Ras you create will nan out of the GTP necessary to B. The cells C. The cells you create will in response to the ex 27. Which of the ollowing statements about molecular switches is false 2 the phosphate from GTP on GTP-binding proteins turning them off Protein kinases A GTP-binding prot transfer the terminal phosphate from ATP onto a protein ein exchanges its bound GDP for GTP to become activated 28. Which of the following statements about the structure of microtubules is falsen Microtubules are built from tubulin dimers that come together to makea B. The two ends of a microtubule are chemically identical, with a-tubulin C.A microtubule is polar, with the two ends being chemically different. hollow structure. exposed at both ends. of the following is primarily responsible for cell crawling: A. Microtubules B. Actin filaments C. Intermediate filaments 30. Which of the following is responsible for maintaining the structure of the nucleus: A. Microtubules B. Actin filaments C. Intermediate filaments 31. Which of the following is responsible for organizing the location of organelles: A. Microtubules B. Actin filaments C. Intermediate filaments 32. Proteins transported into the nucleus: A. Are fully folded B. Are unfolded C. Are unfolded during transport D. Are transported while being translatedExplanation / Answer
26. Ras activation takes place with the help of guanine nucleotide exchange by releasing the bound GDP (inactive form) and binding to GTP,as an exchange, for activation . When a dominant-negative form of Ras binds too tightly to GDP, it will not release GDP easily and will hence stay in its inactive form for a longer duration, and seldom be able to bind to GTP for activation. Because of this, cell division will be at a slower rate in comparison to that with the normal Ras protein. So the correct answer is Option A.
28. Microtubules are formed by tubulin dimers(?- and ?-tubulins), consisting of 13 protofilaments assembled around a hollow core. THe protofilaments are arranged parallel in a head-to-tail array. Microtubules have two distinct ends, giving in a polar nature. Hence, Option B is the correct answer.
29. Cell crawling is a form of cell migration. Since, cells are very viscous, the cytoskeleton helps in movement by producing changes in cell shape. This is made possible by the rapid polimerization of the actin network at the front edge of the cell and an actin network decay at the cell's rear end. This helps in pushing the cell forward and acts as the main force for movement. Hence, actin filaments (Option B) are responsible for cell crawling.
30. Intermediate filaments, as nuclear lamins, are responsible for maintaining the structure of the nucleus. Hence, Option C is correct.
31. Microtubules serve the function of positioning the organelles in a cell's cytoplasm. Option A is the correct answer.
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