The molecule above is known as FURA-2, and it is a dye that is used to bind to Ca(2+) ions within neurons. However, if you look at the molecule, you will realize that it can't actually cross the cell membrane of neurons because it is charged. Thus, the dye needed to be manually injected into cells for it to bind to Ca(2+). With which of the following types of functional groups can you react this molecule such that it would become electrically neutral and more likely to cross the cell membrane?
a) aldehyde b) ketone c) alcohol d) ester e) ether
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C. The reaction of an alcohol with a carboxylic acid will produce an ESTER, which is electrically neutral. This electrical neutrality would permit the molecule to cross the cell membrane since it is no longer charged. Ideally, the functional group we add on should react with the carboxylic acid in order to diminish its charges. Of the options mentioned, only alcohols will react with COOH groups, and thus, the best answer is C.