[Campbell Biology P.1132] Some pesticides inhibit acetylcholinesterase, an enzyme that breaks... | Practice Question

Some pesticides inhibit acetylcholinesterase, an enzyme that breaks down the neurotransmitter acetylcholine ACh in the synaptic cleft. How would this inhibition affect excitatory postsynaptic potentials EPSPs produced by acetylcholine at the postsynaptic membrane?

  • A: EPSPs would be reduced in magnitude due to less acetylcholine binding.
  • B: The duration and magnitude of EPSPs would increase.
  • C: EPSPs would be converted into inhibitory postsynaptic potentials (IPSPs).
  • D: The rate of acetylcholine synthesis by the presynaptic neuron would decrease.

Explanation

Acetylcholinesterase is responsible for breaking down acetylcholine in the synaptic cleft, thereby terminating the signal. If this enzyme is inhibited, acetylcholine will persist in the cleft for a longer duration. This extended presence allows acetylcholine to bind to its receptors on the postsynaptic membrane for a longer period, leading to a prolonged and/or increased opening of ion channels, which manifests as an increased duration and magnitude of excitatory postsynaptic potentials EPSPs .