Rab5 and Rab7 constitute a Rab cascade in the process of endosome maturation. One of the Rab5 effectors is a Rab7-GEF, while one of the Rab7 effectors is a Rab5-GAP. Which of these proteins would you expect to find in early endosomes? Write down Rab5 or Rab7 as your answer.

Indicate true (T) and false (F) statements below regarding intracellular vesicle transport. Your answer would be a four-letter string composed of letters T and F only, e.g. TTTF
( ) The plasma membrane is stiffer and flatter than most intracellular membranes, and its deformation generally requires greater force.
( ) Large molecules such as collagen fibers of about 300 µm in length are highly packed and coiled to fit into normal COPII vesicles of about 80 nm in diameter.
( ) Rab proteins are recruited to membranes following activation by Rab-GEFs.
( ) A Rab and its effector are always on two different membranes that will then fuse.

Reconstitution of vesicle transport in cell-free systems was historically carried out in the presence of isolated "donor" and "acceptor" Golgi stacks. The donor stacks are isolated from cells expressing a viral protein and lacking a processing enzyme. The protein can be transported to the acceptor stacks (that do contain the processing enzyme) and be processed only in the presence of an energy source (such as ATP) and a cytosolic fraction. The transport vesicles that mediate this process are visualized by microscopy. Various compounds can be added to this system to help understand the mechanism of transport. Two such compounds were added in early experiments in the 1980s, both of which blocked transport of the viral protein and resulted in the accumulation of transport vesicles. However, the accumulated vesicles following treatment with one of these compounds (A) appeared to be coated, while those resulting from treatment with the other compound (B) did not. If one of these compounds is a nonhydrolyzable GTP analog and the other one is N-ethylmaleimide, which compound (A or B) do you think represents the GTP analog? Write down A or B as your answer.