Answer:
Ligand-receptor interaction is the first interaction that triggers cell signalling.
Ligands are the hormones, drugs or neurotransmitters that specifically bind with receptors present in cell surface to initiate cell signalling. Ligand binding to the receptor is reversible. Binding of the ligand to the receptor can activate or inactivate receptor. Activation may lead to cell signalling pathways. Inside cells, there are secondary molecules which on activation starts a cascade of reactions. which in-turn regulate the function of the ligand molecule.
At first, the activated receptor relates with G proteins molecules in the cell.
before the ultimate physiological effect of the ligand on the cell's behavior is produced Therefore, the cellular signaling starts as soon as the first messenger (the ligand) binds to its receptor.
hope this helps
 
        
             
        
        
        
If light strikes one receptor, the net effect is to excite the nearest bipolar cell and inhibit other bipolar cells to the side because of the contributions from horizontal cells.
<u>Explanation:</u>
On striking the receptor with light, the nearest bipolar cells respond to the light at the most inside the circumference. The bipolar cells which are outside the circumference responds least to the phenomena. Overall, the net effect thereby when seen, is to excite the nearest bipolar cells.
By the excitement of nearest bipolar cells, other farther cells are inhibited as a result as the horizontal cells are also excited and they contribute to inhibit the bipolar cells which are not near to the receptor cells in the eyes.
 
        
             
        
        
        
Its none of them The person who actually disporved it was Charles Wyville Thompson