A molecule that is detected by our sense of smell first binds to
A) specific receptor proteins on the cilia of receptor cells located in the epithelium of the upper nasal cavity.
B) hairs that extend beyond the mucous layer and line the upper and lower nasal cavities.
C) special mechanoreceptor cells located in the epithelium of the lower nasal cavity.
D) special receptor proteins located at the surface of thermoreceptor cells lining the upper nasal cavity.
Answer: A
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Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium channel and opens it. This is an example of _____
A) a voltage-gated sodium channel B) a voltage-gated potassium channel C) a ligand-gated sodium channel D) a second-messenger-gated sodium channel E) a chemical that inhibits action potentials
Protein synthesis occurs in the
A) nucleus. B) ribosome. C) inclusion. D) cytoskeleton. E) periplasmic space.
Dasypeltis scabra is one of the best studied species of egg-eating snakes. Which of its following characteristics would strongly suggest that it has a built-in egg-cracker?
a. pushing the egg against the rim of the bird's nest b. pushing the egg against ventral hypophyses c. pushing the egg out of the mouth d. pushing the egg against a ribbed trachea
Which of the following skin infections is caused by a protozoan?
A) leishmaniasis B) dermatophytic infections C) otitis externa D) cutaneous candidiasis E) cutaneous anthrax