7. Cel A both survive in tissue but a receptor culture containing serum A produc

Question

7. Cel A both survive in tissue but a receptor culture containing serum A produces do not Factor F is known to stimulate pro in ne A. Cellline protein (R) that B does produce. ce the role of receptor You To test techniques. this receptor protein into ne B, using recombinant DNA response to then test of your various cel cel presence serum for their all lines in the of factor with the results summarized in Table Q16-1 Factor F Cell line Factor F Cells do not proliferate Factor F Cells proliferate Factor F cells do not proliferate Factor F cells do not proliferate B receptor R Factor F Cells proliferate B receptor R Factor F Cells proliferate Table Q16-1 which of the following cannot be concluded from your results above? (a) Binding of factor F to its receptor is required for proliferation of cell line A. (b) Receptor R binds to factor F to induce cell proliferation in cell line A. (c) Cell line A expresses a receptor for factor F (d) Factor F is not required for proliferation in cell line B. 8. All members of the steroid hormone receptor family (a) are cell-surface receptors. (b) do not undergo conformational changes. (c) are found only in the cytoplasm. (d) interact with signal molecules that diffuse through the plasma membrane 9. The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000-dalton protein. You add purified QGF to different types of cells to determine its effect on these cells. When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be true? (a) Because it acts on so many diverse cell types, QGF probably diffuses across the plasma membrane into the cytoplasm of these cells (b) Glial cells do not have a receptor for QGF (c) QGF activates different intracellular signaling pathways in heart muscle cells. fibroblasts, and nerve cells to produce the different responses observed. (d) Heart muscle cells, fibroblasts, and nerve cells must all have the same receptor for QGF

Explanation / Answer

7. Ans is (C)

all other options can be concluded using the table

Factor F clearly requires a receptor but it does not show the receptor protein R to be its receptor necessarily. In presence of receptor protein R in cell line B with F-, there is proliferation in the cell line. This shows protein R is not the receptor for factor F.

8. Ans (D), Interact with signal molecules that diffuse through plasma membrane because they are present inside cell i.e in cytosol or nucleus therefore can accept signals present inside the cells.

9. Ans (C), its has clearly been stated in the question that the signal is extracellular. Extracellular signals can generate various pathways inside the cell. Glial cells may or may not have receptors for the same as the ques refers that there is no effect on cell division or death in these cells. But there can be possibilities for other pathways in glial cells due to the molecule. Different cells may have different receptor types for same molecules. Therefore the molecule is possibly generating dfferent signalling pathways in different cells.

11. Ans (A), nonhydrolyzable analog of GTP would permanently bind to alpha subunit and the the effect of acetylcholine will last long. weak interactions between receptor-acetylcholine and receptor- G protein would lead to weaker effect of the molecular signal. If exchange from GDP for GTP in prevented in alfa subunit the signalling pathway will halt as GTP-alfa subunit compex is required for further signalling.

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