You are studying a hormone receptor that could be either a glucagon receptor or

Question

You are studying a hormone receptor that could be either a glucagon receptor or insulin receptor. Which observation(s) would allow you to conclusively determine you are studying an insulin receptor?

A: Binding of two hormone molecules to the receptor is necessary for activation.
   B: The receptor is found in the membrane of a cell.
   C: Activation of the receptor triggers production of second messengers.
D. Either observation A or B would allow conclusive determination.
E. Either observation B or C would allow conclusive determination.

Explanation / Answer

From the given data,

Insulin receptor is embedded in the plasma membrane, thus it is called transmembrane tyrosine kinase receptor. This receptor is stimulated or activated by the hormone called insulin and other insulin like growth factors called IGF-I and IGF-II. The Insulin receptor mainly play role in the maintenance of blood glucose levels.

Upon binding of insulin to the insulin receptors the phosphorylation of receptor takes place, which lead to activation several kinases in the cytoplasm and expression of various genes. These expressed genes produce various receptor proteins. For example, the GLUT4 receptor is synthesized this mechanism, and these receptors allow the glucose into the liver cell.

Same mechanism would also occur to the glucagon, but it act against to the biological action of insulin. Therefore, Binding of two hormone molecules to the receptor is necessary for activation and activation of the receptor does not trigger production of second messengers.

Thus, the correct option is (A) Binding of two hormone molecules to the receptor is necessary for activation.

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