Why is it more sensible for phosphofructokinase, rather than hexokinase, to be an important control step

1)Why is it more sensible for phosphofructokinase, rather than hexokinase, to be an important control step?
2)What is the energy source that drives the condensation of oxaloacetate and and acetyl CoA to produce citrate?
3)What are the mechanisms that a cell uses to protect against the production of oxygen radicals?
4)Describe how the Citric Acid Cycle is a central metabolic pathway in cells that is used for energy metabolism and functions as an anaplerotic pathway.