# GMAT 考满分题库

Dogs are widely used by the police as biological recognition systems to detect drug smuggling and drug caches. Yet recent evidence suggests that insects, rather than mammals, might be used more effectively in this capacity. In the 1950s, German biologist Dietrich Schneider developed the first method that enabled researchers to record activity in insect olfactory nerves and to identify the compounds or class of compounds that trigger a particular behavioral response. The position of the insect olfactory organs on the surface of its body allows for direct investigation of the systems response. Schneiders technique formed the foundation of an olfactory detection system based upon insects, a system that is at least as effective as the ones based upon mammals.

Insects have olfactory systems that are very similar to those of vertebrates. Insects first detect odors via finger-like protuberances on the antenna, called olfactory sensilla. The odorant molecules pass through pores in the outer cuticle of the sensilla and become attached to an odorant-binding protein. This protein carries the hydrophobic molecules through the lymph fluid found inside the cell and attaches them to receptors on the dendritic projections of a sensory nerve cell. Finally, these receptors send signals to the central nervous system, allowing researchers to detect and interpret the responses.

According to the passage, which of the following roles is played by an odorant binding protein?

• AIt sends a signal to the central nervous system.
• BIt transports a molecule through a cell and fastens it to another cell.
• CIt causes the odorant molecule to become hydrophobic.
• DIt picks up the signal from the olfactory sensilla.
• EIt attaches to an odorant molecule in the outer cuticle of the sensillum.

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