What is a specific example of an electrophile and nucleophile in a cell context?
This is a great question. There's a great example that can be found in what you learned during high school biology!
Converting ATP into ADP involves a chemical reaction called a nucleophillic attack. During this reaction, a lone pair of electrons on an oxygen atom in a water molecule "attacks" the Phosphorus in the terminal phosphate group, removing the the phosphate group from the ATP molecule. During this reaction, the water molecule is the nucleophile and the phosphoryl group is the electrophile.