What organic molecule is built by removing water and what is broken by adding water?

Answer 1

There are several:
Esters are formed by removing water from between an acid and an alcohol.
Peptide bonds (proteins) are formed by removing water from between the carboxyl group of one amino acid and the amino group of the second.
Disaccharides and polysaccharides are formed by removing water from between two (or more) sugar molecules)
Acid Anhydrides are formed by removing water from between two carboxylic acids.

The list goes on and on. Each of these is broken by adding water.