Question

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

Answer 1

Answer:

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.