I believe that the answer is frequency. :)
3.) the circulatory system
Well one big factor would be the ozone layer because it absorbs sun rays. Not sure about the rest.
For a reaction to occur, substrate particles need to collide with each other with enough force (To overcome activation energy), at the right orientation for a successful collision, causing a reaction to occur.
Enzyme catalysts are a type of protein that has a specific 3 dimensional conformation. They have specific reaction sites called active sites. Substrates collides with the enzyme and binds to the active site if it fits to the specific 3 dimensional conformation. This allows bonds to be either formed or broken for reactions to occur.
This process provides an alternative reaction pathway with lower activation energy to enable the rate of reaction to increase.
I think the answer your looking for is Beach.