Insulin is a peptide hormone that is produced by specific cells in the pancreas

Question

Insulin is a peptide hormone that is produced by specific cells in the pancreas following the ingestion of food. This causes some cell types, such as skeletal muscle, to take up the glucose that is now present in the bloodstream. The events stated in a - e below occur during the response of a muscle cell to insulin.

a. The activated receptors initiate the phosphorylation of other protein kinases that carry the signal to glucose transporters waiting in vesicles inside the cell.

b. Insulin binds to the insulin receptor, a transmembrane receptor tyrosine kinase present in the cell membrane of muscle cells.

c. Insulin is destroyed.

d. Two insulin receptors dimerize and attach phosphate groups to the other member, changing their conformations.

e. The signal causes vesicles carrying glucose transporters to move to the cell membrane and glucose is taken into the cell from the bloodstream.

Fill in the blanks with the proper label from the following list: receptor binding, receptor activation, signal transduction, response, or termination.

a. ____________________

b. ____________________

c. ____________________

d. ____________________

e. ____________________

Explanation / Answer

Event (a) corresponds to signal transduction. After activation of receptor, signal is transduced from receptor to effector molecules. Event (b) corresponds to receptor binding. In this insulin binds to insulin receptor. The binding of insulin to its receptor leads to the activation of receptor by means of phosphorylation. Event (c) corresponds to termination insulin is degraded. Since insulin controls glucose homeostasis in the cell hence it must be removed once the blood glucose level drops down. Event (d) corresponds to receptor activation. Event (e) corresponds to response.

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