Which of the following could increase the biological effect

Which of the following could increase the biological effect of messenger molecule X on a given target tissue?

A. increase the affinity of X for its receptor

B. increase the concentration of X available to bind to its receptor

C. increase the number of receptors for X in the target tissue

D. All of the above could increase the biological effect of messenger X

Solution

the answer is D .

a) by increasing the affinity of the messenger molecule with its receptor, a strong interaction between X and its receptor occurs which leads strong intracellular signaling throughout the cell. A strong signal doesnt die out and activates/deactivates various target proteins to exert its biological effects.

b) By increasing the concentration of X, more number of molecules are available to bind the receptors on the cell surface. All the receptors are saturated with its substrate X to initiate the signalling pathway for exerting biological effect in the target tissues.

c) The number of times the signalling pathway is initiated by X is proportional to the number of receptors for X on the cell surface in the target tissue. Each signalling pathway exerts the biological effect individually, therefore increasing the number of receptors on the cell\' surface increases the number of the times a signalling pathway is carried out and thus amplifies the biological effect by X.

Thus in all the three ways stated, the biological effect of X can be increased.