Neonicotinoids are synthetic compounds similar to nicotine that are commonly found in pesticides. Neonicotinoids are considered to be especially suitable as pesticides because they're not toxic to humans and other mammals.
Which statements I - IV are the reasons for this?
I. A larger proportion of synapses in insects are cholinergic compared to mammals.
II. Neonicotinoids are more effective at preventing acetylcholinesterase from breaking down acetylcholine in insects compared to mammals.
III. Acetylcholinesterase in insects cannot break down neonicotinoids.
IV. Neonicotinoids bind more strongly to acetylcholine receptors in insects.
The oscilloscope trace shown below was taken using a digital oscilloscope. It shows an action potential in a hippocampal pyramidal neurone of a potoroo (a small marsupial species) that occurred when the neurone was stimulated with a current pulse.
How many action potentials could be stimulated in this neurone every second?
A research group of geneticists found a fruit fly mutant that shakes vigorously when anaesthetized with ether. Their studies showed that the shaker mutant has K+ channels that do not function properly. An action potential of a normal fruit fly and a shaker mutant is shown below.
Which of the following statements (I - IV) could be possible explanations for the differences between the action potentials?
I. The faulty K+ channels don't open for as long so there is slower diffusion of K+ ions.
II. The faulty K+ channels may be opening early, preventing maximum depolarisation.
III. The faulty K+ channels cause K+ ions to diffuse back into the axon more slowly, resulting in slower repolarisation.
IV. In wild-type drosophila, the functioning K+ channels allow for a faster rate of depolarisation.
