Where is DNA found in cheek cells besides the nucleus?

In addition to nuclear DNA, a small amount of DNA in humans and other complex organisms can also be found in the mitochondria. This DNA is called mitochondrial DNA (mtDNA).

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

this is a good question! i'll do some research and come back when i have the answer!