The ability of a population of fibroblasts to migrate along the surface of a tissue culture dish depends on adhesion between the cell surface and the extracellular matrix molecules coating the dish. The dish is coated with laminin, and the only cell-surface protein capable of binding laminin is a cell-adhesion protein called an integrin. Integrins are integral plasma-membrane proteins that function as heterodimers. Under these conditions the rate at which a fibroblast can migrate along the laminin coated culture dish is proportional to the strength of adhesion between the cell and the laminin substrate. The table below lists the rate of cell migration observed for fibroblasts genetically engineered to generate the indicated phenotypes.

 Which of the following is the most likely explanation for failure of overexpression of the integrin alpha subunit to alter the rate of fibroblast migration?

#Question id: 1371

#Unit 4. Cell Communication and Cell Signaling

A researcher was studying a protein ‘A’ which has been observed to move across cells when an extracellular electrical stimulus is provided. An artificial peptide ‘Z’ was prepared which resembles the structure of pannexins and competitively inhibits pannexon formation. Which one of the following statements will best explain the fate of protein ‘A’ if, the cells are treated with peptide ‘Z’ and then, electrical stimulus is provided.

#Question id: 1370

#Unit 4. Cell Communication and Cell Signaling

H. V. Wilson worked with sponges to gain some insight into exactly what was responsible for holding adjacent cells together. He exposed two species of differently pigmented sponges to a chemical that disrupted intercellular junctions, and the cells of the sponges dissociated. Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. Wilson found that the sponges reassembled into two separate species. The cells from one species did not interact or form associations with the cells of the other species.

How do you explain the results of Wilson's experiments?

#Question id: 1369

#Unit 4. Cell Communication and Cell Signaling

The following statements are made with reference to characteristics of glycosaminoglycans and proteoglycans, which are major constituents of extracellular matrix. Which one of them is incorrect?

#Question id: 1368

#Unit 4. Cell Communication and Cell Signaling

The following statements are made with reference to the characteristic of proteoglycans (major constituents of ECM). Which one of them is incorrect?

#Question id: 1080

#Unit 4. Cell Communication and Cell Signaling

 In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?

#Question id: 1081

#Unit 4. Cell Communication and Cell Signaling

Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?