Activity of the neurotransmitter acetylcholine is brief because it
A) "self-destructs" shortly after leaving the presynaptic neuron.
B) is transported back into the presynaptic neuron.
C) diffuses out of the synaptic cleft.
D) is pumped out of the synaptic cleft by the sodium-potassium pump.
E) is rapidly broken down by enzymes in the synaptic cleft.
E
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The basic chemistry of DNA transposition is a:
A. kinase reaction. B. phosphoryl transfer reaction. C. phosphatase reaction. D. ubiquitination reaction. E. methylation reaction.
Estrogen is a lipid soluble hormone that can easily cross membranes. Knowing this, what can be concluded about estrogen receptors?
A. The receptors would be coupled to a G-protein. B. The receptors would be linked to enzymes that triggered a kinase cascade. C. The receptors would be found inside the cell. D. The receptors would be on the plasma membrane. E. The receptors would also be lipid soluble and able to cross membranes.
Vertebrate locomotion results from the contraction of muscles anchored to what other tissue?
A. bone B. an exoskeleton C. nerves D. the plasma membrane E. each other
The Ames test demonstrates that a chemical is
A. carcinogenic. B. carcinogenic in Salmonella. C. mutagenic in Salmonella. D. carcinogenic in humans. E. mutagenic in humans.