Why do land breezes and sea breezes occur?

 sea breezes occur in areas where a large body of water is located next to land. 
During the day the land becomes warmer than the water. As warm air rises over the land, cold from over the water moves in to fill the space, thus causing a sea breeze. However, during the night, because water holds heat longer than land, the air over the water is warmer than the air over the land. As the warm air over the water rises, the cold air over the land moves in to take it's place, thus causing a land breeze. 

b. to amplify the signal

Explanation:

A multi-enzyme phosphorylation cascade is a series of signaling events where one enzyme phosphorylates to another, then this last enzyme acts to phosphorylate another protein and so successively, thereby triggering a chain reaction that leads to the phosphorylation of hundreds or even thousands of proteins. A multi-enzyme phosphorylation cascade is known to increase the number of activated (phosphorylated) proteins at each step of the signaling cascade. Phosphorylation is a posttranslational modification capable of activating proteins during long periods, thereby a phosphorylation cascade also enables the activation of multiple proteins before these proteins become inactive again.