The inorganic substance removed when amino acids combine during dehydration synthesis is water (H₂O).

Here's why:

* Dehydration synthesis is the process of joining monomers (small molecules) together to form polymers (large molecules) by removing a water molecule.

* In the case of amino acids, the carboxyl group (-COOH) of one amino acid reacts with the amino group (-NH₂) of another amino acid.

* This reaction releases a water molecule (H₂O), forming a peptide bond between the two amino acids.

* This process continues, adding more amino acids to the chain and creating a polypeptide, which can then fold into a protein.

So, the removal of water is essential for the formation of peptide bonds and the construction of proteins from individual amino acids.