I just performed a biology experiment and have a question

I filled 3 test tubes with hydrogen peroxide. Then I added yeast to each one (different amounts). Then, I secured a balloon to each test tube. The balloons expanded.

My question is this:

Is the enzyme the yeast?
Is the substrate the hydrogen peroxide or the gas the mixture produced?

Please help me....

Hydrogen peroxide is usually broken down by an enzyme called catalase. Yeast make catalase so adding different amounts of yeast is equivalent to adding different amounts of catalase. But yeast is more than just the catalase enzyme.

In a chemical reaction the starting materials are the substrates so yes, hydrogen peroxide is the substrate. The things produced are the products so the gas is the product.