16. A class of drugs known as receptor tyrosine kinase inhibitors (RTKIs) inhibi

Question

16. A class of drugs known as receptor tyrosine kinase inhibitors (RTKIs) inhibit signaling from RTK receptors. Which of the following could be a mechanism for how these drugs work? The drugs prevent ATP from phosphorylating the tyrosine residues. a. b. The drugs act as noncompetitive inhibitors and change the shape of the RTKs. c The drugs prevent dimerization of the RTKs. d.All of the above are possible mechanisms for how RTKls inhibit tyrosine kinase activity. 17. In a normal cell, low concentrations of calcium are maintained inside of the cytoplasm and ligand-gated caicium channeis are used for celi signaling. What do you expect to observe in a cell with a defective ligand-gated calcium channel that is constantly open? a higher concentration of calcium inside of the cell than outside of the cell a lower concentration of calcium inside of the cell than outside of the cell c. calcium at equilibrium inside and ouiside of the cell d. a cell that is more sensitive to signaling than normal 18. During digestion the hormone secretin mediates different effects on the stomach and the pancreas. How can one hormone molecule, such as secretin, cause different effects in different cells? a. Se cretin is produced in very large concentration by nearly every tissue of the body Secretin binds to specific receptors found on many kinds of cells, each with nsduction and cellular responses. pond in the same way when secretin binds to the proper receptor. c. All cells res d. Secretin has a flexible shape and can change to bind to multiple receptors. Questions #19-20 pertain to the graph below. 60 40 20 20 100

Explanation / Answer

Ans.16 - (D)

All of the three are possible mechanisms by which RTKs can inhibit tyrosine kinase activity.

Ans.17- (C)

In case of a defective calcium channel that is constantly open, calcium will enter inside the cell until an equilibrium is reached.

Ans.18 - (B)

Different effects of secretin in different target tissues are due to specific receptors present in different tissue which have different signal transduction pathways and cellular effects.

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