An experiment was conducted to investigate the effects of decreases in the pH of the matrix of mitochondria on the ability of the organelle to regenerate ATP molecules efficiently.
Scientists injected different concentrations of hydrogen ions in the matrix spaces of several samples of mitochondria and measured the resulting changes in pH. They then exposed the treated mitochondria to NADH molecules and oxygen.
After 10 minutes, ATP concentrations were measured and recorded in the graph below.
Which of the following is an appropriate conclusion to draw from the results of this experiment?