8- Signal Transduction

Question 1

What are the difficulties in transducing a signal outside the cell into a cellular response inside the cell?

Answer 1

The cells must be able to respond to the signal and molecules causing the signal generally need to be impermeable to the cell membrane.

Question 2

What is a ligand?

Answer 2

A ligand is an extracellular protein that is able to bind to a specific receptor.

Question 3

What is the property of ligands that accounts for the two major classifications of signal transduction?

Answer 3

The property responsible for the two major classifications is the permeability of the ligand.

Question 4

The three histamine receptors (H1, H2, and H3) all bind histamine, but what are the differences in their response to histamine?

Answer 4

The H1 receptor is located in endothelium and smooth muscle and causes a vasodilation affect when acted upon by an antagonist. The H2 receptor is located in the stomach and causes a decrease in gastric acid secretion when acted upon by an antagonist.

Question 5

Ciproxifan is a potent and specific histamine H3 receptor antagonist. Would it be expected that ciproxifan would alleviate allergy symptoms or suppress gastric acidity? Why?

Answer 5

It would not be expected for ciproxifan to alleviate allergy symptoms or suppress gastric acidity, as the H3 receptor is located solely in the brain and neurons.

Question 6

What are three major types of molecular switches for intracellular signaling (hint- the three involve nucleotides in some way), and how is the action of each reversed?

Answer 6

cAMP. cGMP; Ca2+, and phosphatidylinositides (second messengers that affect gene transcription)

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