Acatalyst is a chemical:

found in leaves
which promotes a chemical reaction
which reacts with sunlight
produced by the chloroplast

A catalyst is a chemical ,which promotes a chemical reaction.

Explanation:

A catalyst is a substance which speeds up a reaction without it being changed at the end of the reaction. Each reaction normally needs a specific amount of energy i.e. activation energy . The role of catalyst is to reduce that activation energy needed for a reaction occur.

nanotechnology is a powerful tool in biomaterials research as it creates numerous possibilities for the engineering of functional molecules. nano-bio refers to projected ability to incorporate biomimicry into various materials at nanoscale.  

a boiling water reactor does not boil the water. a pressurized water reactor boils the water faster. a pressurized water reactor is heated directly by the core. a pressurized water reactor does not use fission.