The bonds that hold the two chains of an insulin molecule together are:

The bonds that hold the two chains of an insulin molecule together are two disulfide bonds.

Insulin molecule is made up of two peptide chains. These chains are referred to as the A and B chains. The A and B chains are help together by the two disulfide bonds present between them. The A chain has an additional disulfide bond inside it. The A chain is 21 amino acids long and the B chain is 30 amino acids long in most of the species.