Mitochondrial inner membrane fragments that contain ATP synthase can be isolated in the lab. Under appropriate conditions, these
membranes can be caused to form inside-out vesicles, such that the side of the membrane normally facing the mitochondrial matrix is on the outside of the vesicle. (a) These vesicles are placed in a buffer at pH 7.0, which also contains ATP, ADP and inorganic phosphate (P), at roughly equal concentrations. The pH inside the vesicles is also 7.0. Under these conditions, what reaction do you expect the vesicles to catalyze? The experiment is repeated, but is now set up so that the pH inside the vesicles is 6.5, and the pH of the buffer containing ATP, ADP and P, is 8.5. What reaction do you expect the vesicles to catalyze under these conditions? Briefly explain your reasoning in both cases
The optimum pH of ATP synthase is 6.4 therefore maximum activity will occur at pH7 by the vesicle, however because the concentration of the three , is relatively the same , and exhibited equal effects on the pH, catalysis by the vesicle will not take place BECAUSE NO HYDROGEN ION IS AVAILABLE to supply the energy
Generally the synthase activity decreases with drops in pH. The lower pH of 6.5 from the set point value , will affect catalysis.
The low pH lead to increase in concentration of base in the buffer solution. Therefore more H + are produced .for the synthesis of ATP. The vesicle catalyzed ATP production. But the increase in hydrogen ion concentration with time affect the 3 dimensional structure of the ATPase synthase enzyme in the vesicle and increases the inhibitory effect of ADP therefore the vesicle stops the catalysis.
