Generally speaking, enzymes (which amylase happens to be) do not undergo any permanent structural change while carrying out their function. Some do exhibit transient conformational change during a reaction, but upon completion regain their original form.
So your initial assumption is correct: once amylase has finished catalyzing the breakdown of starch into less complex sugar molecules, it moves on and repeats the process over and over.
The cel theory is important because it affects nearly every aspect of biology, from our understanding of life, death, to how we manage diseases and more.
