Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 11

Inverted Vesicles. An important advance in transport research was the development of methods for making closed membrane vesicles that retain the activity of certain transport systems. One such system uses resealed vesicles from red blood cell membranes, in which the orientation of membrane proteins may be either the same as in the intact cell (right side out)or inverted (inside out). Such vesicles have demonstrable ATP- driven Na + /K + pump activity. By resealing the vesicles in one medium and then placing them in another, it is possible to have ATP, sodium ions, and potassium ions present inside the vesicle, present outside the vesicle, or not present at all.
(a)Suggest one or two advantages that such vesicles might have compared to intact red blood cells for studying the Na+/K+ pump. Can you think of any possible disadvantages
(b)For the inverted vesicles, indicate whether each of the following should be present inside the vesicle (I), outside the vesicle (O), or not present at all (N)in order to demonstrate ATP hydrolysis: Na + , K + , and ATP.
(c)If you were to plot the rate of ATP hydrolysis as a function of time after initiating transport in such inverted vesicles, what sort of a curve would you expect to obtain