the biochemical properties of the respiratory enzyme complexes required for oxidative phosphorylation. Your initial goal is to measure proton pumping by the NADH dehydrogenase complex. You mix purified NADH dehydrogenase complex with phospholipids and a pH indicator dye that changes color at acidic pH, and you follow a protocol for making liposomes. After verifying that the protein complex was incorporated into liposomes, you add NADH and incubate at 37°C. You are dismayed to observe no color change in the pH indicator dye.

One lab partner says the result is not surprising, because you forgot to add a key component. What is this key component? describe why it is important.