Question

Investigators introduce two proteins into the membrane of artificial lipid vesicles: (1) an ATP synthase isolated from the mitochondria of cow heart muscle, and (2) a light-activated proton pump purified from the prokaryote Halobacterium halobium. The proteins are oriented as shown in the diagram. When ADP and P; are added to the external medium and the vesicle is exposed to light, would this system produce ATP? H LIGHT protein pump ATP synthase Choose one: O No, because no electron-transport chain is present. O Yes, because the proton pump will generate a proton gradient that ATP synthase can use to synthesize ATP. O No, because cows and prokaryotes are so distantly related that their proteins cannot be expected to work together. O No, because protons are small enough to pass freely in and out of an artificial lipid vesicle. O No, because ATP synthase is not oriented correctly.

Answer 1

Answer: No, because the ATP synthase is not oriented correctly. (the ATP synthase needs to be oriented opposite to what is shown here in order to generate ATP. The F1 portion, i.e. the bulbous portion generates ATP from ADP and Pi, and hence needs to face outside the vesicle, and not inside)

Elaborate electron transport chain is not needed as long as there is at least one proton pump present to transport protons inside. This proton pump will get activated by light and transfer proton to the inside of the vesicle. The origin of the proteins do not matter as they are working in an artificial system. Protons can never pass through a hydrophobic lipid membrane as protons are charged. Hence the first five options are wrong.