A protein contains an N-terminal ER signal sequence followed by several negatively charged amino acids, an internal ER stop-transfer sequence, and an internal ER start-transfer sequence (in order from N-terminal to C-terminal). The signal sequence is cleaved by signal peptidase upon lateral release from sec61. How will the protein orient in the ER membrane?

A. Lumenal N-terminal, cytosolic C-terminal
B. Lumenal N-terminal, cytosolic protein loop, lumenal C-terminal
C. Cytosolic N-terminal, lumenal protein loop, cytosolic C-terminal
D. Membrane-bound N-terminal, lumenal protein loop, cytosolic protein loop, lumenal C-terminal
E. The protein will be soluble and released into the ER lumen

Female luna moths (actias luna) attract males by emitting chemical signals that spread through the air. a male hundreds of meters away can detect these molecules and fly toward their source. the sensory organs responsible for this behavior are the comblike antennae visible in the photograph shown here. each filament of an antenna is equipped with thousands of receptor cells that detect the sex attractant. based on what you learned in this chapter, propose a hypothesis to account for the ability of the male moth to detect a specific molecule in the presence of many other molecules in the air. what predictions does your hypothesis make? design an experiment to test one of these predictions.