Only the correct key will fit snugly into the lock and allow a turn of the catalytic mechanism. The wrong key will not fit into the lock, or it will fit so poorly that turning the mechanism is difficult or even impossible. Just as real tumblers directly interact with the notches on keys, so these amino acid residues directly interact with chemical groups on the coenzymes. Hydrogen bonds are the same bonds that hold molecules of water together. They are sensitive to both the angle and the distance of the interacting atoms, which accounts for the ease of boiling water, whereby hydrogen bonds are broken to liberate free water molecules as gas.
Electrostatic interactions occur between charged atoms.
Oppositely charged atoms attract one another. For example, a crystal of common salt is held together by positively charged sodium ions interacting with negatively charged chloride ions. Electrostatic interactions diminish with increasing distance, but remain insensitive to changes in angle. Steric-packing effects describe the physical fit of one molecule against another, much as the parts of a machine must fit snugly against one another. These same five amino acids are replaced by other residues in the NAD-dependent dehydrogenases.