Question

There are at least 3 molecular reasons why the same signaling molecule causes different cells to change their behavior in different ways.

Explain 1 one these molecular mechanisms in detail.  

Answer 1

Explanation of the molecular mechanism in which same signalling molecule causes different cells to change their behaviour in different ways.

Regardless of the nature of the signal, the target cell responds by means of a specific protein called a receptor, which specifically binds the signal molecule and then initiates a response in the target cell.

So different receptors relay different signalling responses regardless of same signal molecule.

The extracellular signal molecules often act at very low concentrations, and the receptors that recognize them usually bind them with high affinity.

In most cases, these receptors are transmembrane proteins on the target cell surface.

When they bind an extracellular signal molecule (a ligand), they become activated and generate a cascade of intracellular signals that alter the behavior of the cell.

In other cases, the receptors are inside the target cell, and the signal molecule has to enter the cell to activate them: this requires that the signal molecules be sufficiently small and hydrophobic to diffuse across the plasma membrane

Figure- The binding of extracellular signal molecules to either cell-surface receptors or intracellular receptors