Life Science CSIR NET JRF - Cell Biology questions - Part - 4

31. Imagine two solutions separated by a selectively permeable membrane which allows water to pass, but not sucrose or glucose. The membrane separates a 0.2 M sucrose solution from a 0.2 glucose solution. With time how will the solutions change?

(a) Nothing happens because the two solutions are isotonic to one another.
(b) Water enters the sucrose solution because the sucrose molecule is a disaccharide, and is larger than the monosaccharide glucose.
(c) Water leaves the sucrose solution because the sucrose molecule is a disaccharide, and is larger than the monosaccharide glucose.
(d) The sucrose solution is hypertonic and will gain water because the total mass of sucrose is greater than that of glucose.

32. During cytokinesis in plants:
(a) a bundle of actin microfilaments called the contractile ring, pinch the cell in half
(b) small vesicles, directed by the phragmoplast, move to the spindle
(c) a cleavage furrow encircles the cell
(d) cytoplasmic division is called cleavage

33. Progression through the eukaryotic cell cycle is regulated by:
(a) microtubules (b) the p53 gene
(c) cyclin-dependent kinases (d) DNA ligase

34. The result of the operation of an electrogenic pump would be
(a) an electrochemical gradient on the cell membrane
(b) a resting potential across the membrane
(c) plasmolysis
(d) a cell with a positively charged interior

35. A plant cell is placed in a solution whose solute concentration is twice as great as the concentration of the cell cytoplasm. The cell membrane is selectively permeable, allowing water but not the solutes to pass through. What will happen to the cell?
(a) No change will occur because it is a plant cell.
(b) The cell will shrivel because of osmosis.
(c) The cell will swell because of osmosis.
(d) The cell will shrivel because of active transport of water.

36. One consequence of the sidedness of the plasma membrane is that
(a) molecules that begin on the inside face of the ER end up on the inside face of the plasma membrane
(b) the asymmetrical distribution for membrane proteins, lipids, and carbohydrate must be determined when the membrane is first constructed
(c) some proteins on the cytoplasmic side of the membrane are attached to the cytoskeleton
(d) the inside of an ER vesicle is topographical equivalent to the extra cellular surface of the plasma membrane

37. The p53 gene:
(a) is the most frequently mutated gene in human cancer
(b) can lead to cell cycle arrest at the G1 checkpoint
(c) can trigger apoptosis.
(d) all of the above

38. During the Ras pathway:
(a) cytoplasmic protein kinases are activated
(b) the growth factor receptor is dephosphorylated
(c) growth factors bind to receptors in the cytoplasm
(d) leads to the production of translation factors

39. If a DNA molecule has a deaminated base, it will be repaired by:
(a) by excision repair pathways
(b) with the help of repair endonucleases
(c) by base excision repair
(d) with the help of DNA glycosylases

40. A benign tumor is one in which the cancerous cells:
(a) have an unusual number of chromosomes
(b) can divide indefinitely if an adequate supply of nutrients is available
(c) migrate from the initial site of transformation to other organs or
(d) remain confined to their original site

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