Question

where does ATP generating chemical reaction occur in mitochondria​

Answer 1

in the matrix ( the innermost across the inner membrane)

Answer 2

The process is called oxidative phosphorylation and it happens insidemitochondria. In the matrix of mitochondriathe reactions known as the citric acid or Krebs cycle produce a chemical called NADH. NADH is then used by enzymes embedded in the mitochondrial inner membrane to generate adenosine triphosphate (ATP).