"describe the mechanism of feedback inhibition and the role this process plays in controlling enzyme activity."

In biochemistry, feedback inhibition occurs when the end product produced by the reaction using an enzyme, interacts with the enzyme again such that it inhibits the initial reactants. This is important in metabolic reactions to control too much production of amino acids or too much work done by enzymes to break down macromolecules. 

Geo-tropism is one, that's when the roots grow towards gravity.
Photo-tropism is the other, this is when roots grow away from the light.