What is required for odorant molecules to activate olfactory receptors?

What is required for odorant molecules to activate olfactory receptors?

• A. Bind to transport proteins that deliver them to olfactory dendrites.
• B. Must be detected by retinal receptors.
• C. Must be ingested and metabolized.
• D. Must be phagocytosed by supporting cells.

Answer: (A)

Olfactory detection hinges on delivering odorant molecules to the receptors on the olfactory sensory neurons. In the nasal mucus, hydrophobic odorants are bound by odorant-binding proteins that shuttle them to the dendritic membranes of the olfactory neurons. There, the odorant binds to a receptor, typically a G protein–coupled receptor, triggering a signaling cascade that depolarizes the neuron and sends a signal to the brain. This delivery step—odorants binding to transport proteins that carry them to the olfactory dendrites—is essential for activation of the receptors. The other options don’t fit: vision relies on retinal receptors, odorants aren’t required to be ingested and metabolized to be detected, and supporting cells don’t phagocytose odorants as part of normal olfactory activation.

Olfactory detection hinges on delivering odorant molecules to the receptors on the olfactory sensory neurons. In the nasal mucus, hydrophobic odorants are bound by odorant-binding proteins that shuttle them to the dendritic membranes of the olfactory neurons. There, the odorant binds to a receptor, typically a G protein–coupled receptor, triggering a signaling cascade that depolarizes the neuron and sends a signal to the brain. This delivery step—odorants binding to transport proteins that carry them to the olfactory dendrites—is essential for activation of the receptors.

The other options don’t fit: vision relies on retinal receptors, odorants aren’t required to be ingested and metabolized to be detected, and supporting cells don’t phagocytose odorants as part of normal olfactory activation.