Chemistry Pic of the Week

cucumber beetle - Copy

I seem to be on an insect kick with these… this is a cucumber beetle in a squash flower. It’s kind of amazing to still be seeing all this insect activity in October. Cucumber beetles are pests that spread plant viruses. Interestingly, a pesticide has been developed for them that combines cucurbitacins (which are naturally found in cucumbers and attract the beetles) with carbaryl, a deadly nerve agent. Carbaryl is very similar in structure with acetylcholine, a neurotransmitter which is used to send nerve impulses to the muscles.

ccuA

carbarylacetylcholine

The neurotransmitter has to to be cleared before another signal can be sent. It’s the job of another chemical, acetylcholinesterase, to break down the acetylcholine so another signal can be sent. What carbaryl does is bind up the acetylcholinesterase, because its shape and chemical structure is similar to the nuerotransmitter, so that it can’t clear the neurotransmitter, leading to paralysis and asphyxiation of the insect.

Acetylcholine and acetylcholinesterase are also present in humans where they do the same things, although it would take larger quantities of pesticide to have the same effect on humans.

 

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